744P F ATA 24 Electrical Power

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Training Manual

747

This manual has been prepared by Alteon Seattle, Washington for theBoeing Commercial Airplane Group.

THIS MANUAL IS FOR TRAINING PURPOSES ONLY.

NO MAINTENANCE ACTION SHOULD BE TAKEN AS A RESULT OF INFORMATION CONTAINED IN THIS MANUAL.

- ALTEON PROPRIETARY RIGHTS ARE INCLUDED IN THE INFORMATION DISCLOSED HEREIN. RECIPIENT BY ACCEPTING THIS

DOCUMENT AGREES THAT NEITHER THIS DOCUMENT NOR THE INFORMATION DISCLOSED HEREIN NOR ANY PART THEREOF SHALL BE

REPRODUCED OR TRANSFERRED TO OTHER DOCUMENTS OR USED OR DISCLOSED TO OTHERS FOR MANUFACTURING OR FOR ANY

OTHER PURPOSE EXCEPT AS SPECIFICALLY AUTHORIZED IN WRITING BY ALTEON

UNPUBLISHED - ALL RIGHTS RESERVED UNDER COPYRIGHT LAWS

(c) 2003 Alteon Training L.L.C.



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ALTEON PROPRIETARY - Copyright (c) - See title page for details

ELECTRICAL POWER -- INTRODUCTION

General

The electrical power system has components that supply

and control electrical power to the airplane. These

systems include:

- External/APU power

- Engine power

- DC power

- Standby power

- Load distribution

- Indicating.

External/APU Power

External/APU power supplies electrical power during

ground operations. It includes two external power

sources and two APU generators.

Engine Power

Engine generators supply electrical power for all usual

flight operations. There are four integrated drive

generators (IDG).

DC Power

The dc power system supplies those loads for which dc

power is necessary. It includes the batteries and

transformer rectifier units.

Standby Power

Standby power supplies power for important loads when

the primary source fails.

Load Distribution

The load distribution system controls and sends ac and

dc power to all parts of the airplane.

Indicating

Indicating includes the electrical power interfaces

with EICAS and the central maintenance computer and

related displays.

- 2 -

APU and main battery



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ELECTRICAL POWER - INTRODUCTION

IDG

APU

APU

IDG

EXTERNAL

MAIN

MAINIDG

INDICATING DISTRIBUTIONSTANDBY

DC

ENGINEEXTERNAL/APUPOWER

POWER CARTS

BATTERY

EQUIPMENT

CENTER

POWER

POWER

BATTERY

GENERATORS

POWER

IDG

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ELECTRICAL POWER -- SYSTEM SIMPLIFIEDELECTRICAL POWER -- SYSTEM SIMPLIFIED

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ELECTRICAL POWER -- SYSTEM SIMPLIFIED

General

The ac and dc distribution systems send electrical

power to all parts of the airplane. The ac distribution

system has these buses:

- AC 1, 2, 3, and 4

- F/O transfer (AC F/O XFR)

- Capt transfer (AC CAPT XFR)

- AC standby (AC STBY)- Ground handling (AC GH)

- Ground service (AC GS).

The dc distribution system has these buses:

- DC 1, 2, 3, and 4

- DC ground handling (DC GH)

- APU hot battery (APU HOT BAT)

- Main hot battery (MN HOT BAT)

- Main battery (MN BAT)

- APU battery (APU BAT).

AC Buses 1, 2, 3, and 4

The IDGs, APU generators, or external power carts

supply power to the ac buses. An IDG connects to its

related bus when the related generator circuit breaker

(GCB) closes. The IDGs are in parallel when the related

bus tie breakers (BTB) and GCBs close. The

synchronizing (synch) bus has two sections that connect

by a split system breaker (SSB). With correct use of

the breakers, a generator can supply power to one or

more load buses and one or more IDGs can operate in

parallel. The power output of the APU generators orexternal power carts can also connect to the load buses

through the auxiliary power breakers (APB) or external

power contactors (XPC).

Transfer Buses

There are two transfer buses, the captain and the first

officer. The captain transfer bus usually gets power

from ac bus 3. If ac bus 3 does not have power, thetransfer bus connects to ac bus 1 for power. The first

officer transfer bus usually gets power from ac bus 2

but connects to ac bus 1 if ac bus 2 does not have

power.

AC Standby Bus

The standby ac bus usually gets power from ac bus 3 but

connects to the static inverter if ac bus 3 does not

have power, the battery switch is on, and the standby

power switch is in the AUTO position.

The APU AC standby bus is an alternative power source

for the captain primary instruments when power to those

instruments fail, the battery switch is ON, and the

standby power switch is in the AUTO position.

Ground Handling Bus

The ground handling bus gets power from the APU

generator 1 or the external power receptacle 1 through

the ground handling relay (GHR). The bus gets power

automatically when external power or APU power is

- 5 -

so it's necessary to connect external powerreceptacle 1(the left one as you face the

receptacle) to operate low cargo door.



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747 TRAINING MANUAL


ELECTRICAL POWER -- SYSTEM SIMPLIFIED

available. If APU and external power are available at

the same time, external power connects to the ground

handling bus. The ground handling bus does not get

power in flight.

Ground Service Bus

The ground service bus always gets power from the ac

bus 1 if that bus has power. If ac bus 1 does not have

power, the ground service bus can get power from

external power 1 or APU generator 1 through the ground

service select relay (GSSR) and ground service transfer

relay (GSTR).

DC Buses 1, 2, 3, and 4

Dc buses 1, 2, 3 and 4 gets power from transformer

rectifier units (TRUs). The dc buses supply this power

through dc isolation relays (DCIRs). The bus tie switch(P5) controls the dc isolation relays.

DC Ground Handling Bus

The dc ground handling bus gets power when the ac

ground handling bus has power. TRUs supply the dc

power. These TRUs are not the same as the TRUs on the

main dc buses.

DC Cargo Handling Bus

The dc cargo handling bus gets power when the ac cargo

handling bus has power. A TRU supplies the dc power.

The TRU is the same as the TRU used on the dc ground

handling buses.

Main and APU Hot Battery Buses

The main and APU hot battery buses get power from the

main and APU batteries. When the ground service bus has

power, the battery chargers supply power to the buses

and charge the batteries.

Main and APU Battery Buses

The main and APU battery buses usually get power from

dc bus 3. If dc bus 3 does not have power and the

battery switch is on, the buses get power from their

related batteries.

- 6 -



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1

1

ELECTRICAL POWER - SYSTEM SIMPLIFIED

APU AC STBY BUSAPU STAT INV

BAT SW

STAT INV

MN BAT

MN HOT BATAPU HOT BAT

DC GH

T/R B/C B/C

AC GSAC GH

GSTR

BOTH STATIC INVS ARE OFF WHEN STBY POWER SW IS OFF

AC 1

DC 1

AC 2

DC 2

AC CAPT XFRAC F/O XFR

AC STBY

APU BAT

AC 3

DC 3

AC 4

DC 4

EXT 1

XPCSSB SYNCH BUS

GSSRGHR

T/R 1 T/R 2

XPCAPB

EXT 2

BTB

GCB

DCIR

OFF

STBY

T/R 4T/R 3

AUTO

BAT

APB

APU1

PWR SW

SYNCH BUS

APU2

IDG1

IDG2

IDG3

IDG4

- 7 -



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ELECT PWR -- MANUAL CONTROL - SYSTEM CONTROL PANEL

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General

The electrical system panel is in the flight deck on

the P5 overhead panel. The panel has switches and a

selector which gives automatic or manual control of the

electrical power system.

Drive Disconnect

The drive disconnect switch (DRIVE DISC) is a momentaryaction switch that has a guard. You push this switch to

disconnect the IDG input drive from the engine.

The amber DRIVE light in the switch gives an indication

of low pressure or high temperature of the IDG oil.

Generator Control

The generator control switch (GEN CONT) is an alternateaction switch. Operation of the switch to the latched

in position closes the generator field relay and lets

the generator circuit breaker (GCB) close when good

power is available. Operation to the out position opens

the generator field relay and the GCB.

ON is a mechanical indication of automatic GCB

operation. OFF is an amber light indication of an open

GCB.

Bus Tie

The bus tie switch (BUS TIE) is an alternate action

switch. Operation of the switch to the latched in

position gives automatic operation of the bus tiebreaker (BTB) and dc isolation relay (DCIR). Operation

to the out position opens the BTB and the DCIR.

AUTO is a mechanical indication of automatic BTB and

DCIR operation. ISLN is an amber light indication of an

open BTB.

External Power 1 and 2

The external power switch (EXT PWR 1/EXT PWR 2) is a

momentary action switch. You push the switch to open or

close the external power contactor if external power is

available.

AVAIL is a white light indication of good external

power connected to the airplane. ON is an indication of

a closed external power contactor.

APU Generator 1 and 2

The APU generator switch (APU GEN1/APU GEN 2) is a

momentary action switch. You push the switch to open or

close the auxiliary power breaker (APB) if auxiliary

power is available.

AVAIL is a white light indication of good APU power. ON

is an indication of a closed APB.

Battery

The battery switch (BATTERY) is an alternate action

switch that has a guard. Operation of the switch to the

- 9 -

switchWlatchedinv—OM

GCBW(openv—rÀaK

switchW(latched inv—OM

BTBW(openv—r a



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747 TRAINING MANUAL



latched in position connects the battery to the main

battery bus.

ON is a mechanical indication of a closed battery

switch. OFF is an amber light indication that the

battery switch is off.

Utility

The utility bus switch (L-UTILITY-R) is an alternate

action switch. Operation of the switch opens or closes

the electrical load control unit (ELCU) relays. The

left and right utility bus switches each control two

galley ELCUs and two utility bus ELCUs.

ON is a mechanical indication of a closed utility bus

switch. OFF is an amber light indication of an open

ELCU(s). The OFF indication does not show during load

shedding.

Standby Power

The standby power switch is a three position rotary

switch. In OFF the standby power is off.

In AUTO if there is a loss of ac bus three:

- Ac standby bus moves to the static inverter- Main battery bus moves from dc bus 3 to the main

battery

- APU battery bus moves from dc bus 3 to the APU

battery.

In BAT the main battery connects to the main battery

bus and the APU battery connects to the APU battery bus

if the battery switch is on. The static inverter also

supplies the ac standby bus.

- 10 -

static inverters are off when standbypower SW is off.

ON,OFFSêf/Nã‹hswitchvîRMv—OMn



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ELECT PWR - MANUAL CONTROL - SYSTEM CONTROL PANEL

wAUTO

ISLNa

DRIVE

w

a

w

a

ON

OFF

1 32

BUSTIE

GENCONT

DRIVEDISC

BUS

wAUTO

ISLNa

DRIVE

w

a

w

a

ON

OFF

BUS

wAUTO

ISLNa

DRIVE

w

a

w

a

ON

OFF

BUS

wAUTO

ISLNa

DRIVE

w

a

w

a

ON

OFF

BUS

4

STANDBY POWER

OFFAUTO

BAT

L - UTILITY - R

EXT PWR 1 APU GEN 1

ON

OFF

BATTERY

ONw

aOFF

ONw

a

OFF

ONw

aON ON ON

w

AVAIL

APU GEN 2 EXT PWR 2

APU

ONOFF START

SHUTTER CLOSED

w

AVAIL w

AVAIL w

AVAIL w

SHUTTEROPEN/ON EXPOSED

- 11 -



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General

The generator manual reset panel is in the flight deck

on the aft overhead panel (P461). The panel has seven

momentary toggle switches that have guards. It gives

indication and manual control for the:

- Engine generator field relays

- APU generator field relays

- Split system breaker (SSB).

ELECT PWR -- MANUAL CONTROL - GENERATOR MANUAL RESET PANEL

- 12 -



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ELECT PWR - MANUAL CONTROL - GENERATOR MANUAL RESET PANEL

GEN FIELD MAN RESET

1 2 3 4

FIELDOFF w

1 APU 2SPLIT SYSTEM

BREAKER

OPENw

FIELDOFF w

FIELDOFF w

FIELDOFF

w

FIELDOFF w

FIELDOFF w

- 13 -



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747 TRAINING MANUAL


General

You can connect one or two external power sources to

the airplane.

External power comes from external power carts or gate

power through two receptacles on the right forward side

of the airplane. From the receptacles the power goes to

external power contactors in P714 and P715. These

contactors connect the external power to the airplane

electrical system.

ELECT PWR -- EXT POWER - SOURCES

- 14 -



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ELECT PWR - EXT POWER - SOURCES

P714

P715

EXTERNAL

EXTERNALPOWER CARTS

POWERRECEPTACLES

- 15 -



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General

All of the components in the external power system are

in the main equipment center (MEC) except the

electrical system control panel, generator manual reset

panel, and the external power panel. The external power

system includes these components:

- External power panel with two receptacles

- Ground handling relays (2)

- Current transformers (4)- External power contactors (2)

- Bus control units (2)

- Transformer rectifier units (2)

- Ground service relays (4)

- Split system breaker

- Generator manual reset panel

- Electrical system control panel.

ELECT PWR -- EXT POWER - COMPONENTS

- 16 -



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ELECT PWR - EXT POWER - COMPONENTS

GENERATOR MANUAL

EXTERNAL POWER

ELECTRICAL SYSTEM

BUS CONTROL

TRANSFORMER

EXTERNAL POWER PANEL

CURRENT

GROUND SERVICE

SPLIT SYSTEM

GROUND HANDLING

w

FIELD

GEN FIELD MAN RESET

wOFFFIELD

wOFFFIELD

wOFFFIELD

OFF wOFFFIELD

w

OPEN

BREAKERSPLIT SYSTEM

2APU1

wOFFFIELD

4321

BREAKER

RESET PANEL (P461)

RELAY (4)

RECTIFIERUNIT (2)

UNIT (2) CONTACTOR (2)

TRANSFORMER (4)

RELAY (2)

(P36)

CONTROL PANEL (P5)

- 17 -



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747 TRAINING MANUAL


General

Two external power carts supply three-phase, 400 Hz,

115v ac to the airplane through the external power

receptacles. Before the power can connect to the

airplane systems, two bus control units (BCUs) monitor

the power for quality. BCU 1 monitors the power from

the aft receptacle. BCU 2 monitors the power from the

forward receptacle. The BCUs make a check for these:

- Plugs are fully in- Voltage, frequency, and phase are correct

- Plug interlock system does not have a short to the

main feeder wires.

When the BCUs find that all of these conditions are

correct, they cause the external power AVAIL lights to

come on at the electrical system control panel in the

flight compartment.

Ground Handling Bus

When BCU 1 causes the external power AVAIL light to

come on, it also energizes the ground handling relay

(GHR). This gives power to the ground handling bus

(GHB). Cargo loading, cleaning outlets, and fueling are

some of the systems on the GHB.

Ground Service Bus

There is a ground service switch at door 2 left.

Operation of this switch gives a signal to BCU 1 to

energize the ground service relays. These relays

connect power to the ground service bus (GSB). Cabin

lights and the battery chargers are some of the systemson the GSB.

External Power

The two momentary switches EXT PWR 1 and EXT PWR 2 are

on the electrical system control panel. When you push

EXT PWR 1, it gives a signal to BCU 1 to close its

related external power contactor (XPC). The ON light in

the switch comes on, and the AVAIL light goes off. BCU2 closes the split system breaker (SSB) at this time if

no other power is on the synchronizing (synch) bus. The

aft power cord now supplies power to the airplane. When

you push EXT PWR 2, it gives a signal to BCU 2 to open

the SSB and close its related XPC. The ON light in the

switch comes on, and the AVAIL light goes off. EXT PWR

1 now supplies power to the left side of the synch bus,

and EXT PWR 2 supplies power to the right side of the

synch bus.

ELECT PWR -- EXT POWER - OPERATION

- 18 -

E,F pin

using the power from GHB , it's not necessary to

operate the EXT POWER 1&2 SW.

GSSRGSTR



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GROUNDGROUND

SSB

TRIP

CLOSE SSB

wAUTO

BUSwAUTO

wAUTO

wAUTO

STANDBY POWER

OFFAUTO

BAT

L - UTILITY - R

EXT PWR 1 APU GEN 1

ON

OFF

BATTERY

ONw

a

w w

AVAIL

OFF

ONw

a

OFF

ONw

aON

w

AVAIL

ON

w w

AVAIL

ON

w

AVAIL

APU GEN 2 EXT PWR 2

APU

ONOFF START

BCU 1

EXTERNAL

TRIP

BCU 2

LEFT

GSR

RIGHT

AFT (LEFT) (NO. 1) FWD (RIGHT) (NO. 2)

OPEN/CLOSEOPEN/CLOSE

XPC 1

XPC 1 XPC 2

XPC 2

ELECTRICAL SYSTEM CONTROL

EXTERNAL POWERRECEPTACLE

EXTERNAL POWERRECEPTACLE

PANEL (P5)

POWER OK

OPEN/CLOSE

SERVICE

OPEN/CLOSE

SERVICESELECTED

CLOSE

SYNCH BUS SYNCH BUS

GHB

GSB

ELECT PWR - EXT POWER - OPERATION

GHR

- 19 -



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747 TRAINING MANUAL


General

The external power panel is on the right side of the

fuselage aft of the nose wheel well doors. The panel

includes:

- Two 250 ampere receptacles (the aft receptacle is

primary because the ground handling bus gets power

through it)

- AC CONNECTED lights that come on when good quality

power is available to the airplane.- POWER NOT IN USE lights that show when external

power or ground service is not in use.

ELECT PWR -- AC EXT POWER - POWER PANEL

- 20 -



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ELECT PWR - AC EXT POWER - POWER PANEL

AC CONNECTED LIGHT

AC CONNECTED

FWDAFT

POWER

EXTERNAL

NOT IN USE

LIGHTSLIGHT

POWERRECEPTACLE

(LEFT NO. 1) (RIGHT NO. 2)

- 21 -

E,F pin



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General

There are two inter-changeable ground handling relays

(GHR) in P714 in the MEC. They use 28 volts dc for

control and are 3 pole, double throw, center off type

relays. BCU 1 energizes these relays to connect the

correct power source for the ground handling bus. The

two power sources are external power 1 and APU

generator 1.

ELECT PWR -- AC PWR DISTRIBUTION - GROUND HANDLING RELAYS

- 22 -



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ELECT PWR - AC PWR DISTRIBUTION - GROUND HANDLING RELAYS

DC FROM

FROM APU

DC FROM

TO

FROM AFT EXTERNAL

P714

POWER RECEPTACLE3 PHASE 400 HZ 115/200V

BCU 1

GROUNDHANDLING

BUSSES

BCU 1

GENERATOR 13 PHASE

400HZ115/200V

- 23 -



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General

There are four current transformers (CT) related to

external power. They are in P714 and P715 in the MEC.

The CTs are used for:

- Metering (data sent to BCUs for percent load

indications on EICAS)

- Differential fault protection (data used by the

BCUs)

- Load reduction (data sent to BCUs for loadreduction circuits).

Characteristics

Each transformer assembly has a toroidal shaped core

with secondary winding wires that connect to an output

connector. Main ac feeder lines goes through the large

holes in the transformer and are the primary winding

for each transformer core. The turns ratio of all thewindings is 1000 to 1. If the primary winding (feeder

line) is 115 volts ac, secondary winding voltage is as

much as 115,000 volts with the connector off (no load).

Usually secondary voltages are very low because the

secondary loads have a low resistance.

WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT

CONNECTION WITH THE FEEDER LINES POWERED. THE

POTENTIALLY HIGH VOLTAGES COULD DAMAGE THETRANSFORMER OR RESULT IN INJURY TO PERSONNEL.

ELECT PWR -- AC EXT POWER - CURRENT TRANSFORMER

- 24 -



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ELECT PWR - AC EXT POWER - CURRENT TRANSFORMER

CONNECTOR

P714

P715

1000

1000

1000

A PHASE

B PHASE

C PHASE

FEEDERLINES

- 25 -



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General

There are two external power contactors (XPC) that

connect external power to the airplane synch bus. They

are in the MEC. The contactor for the aft external

power receptacle is in P714. The contactor for the

forward external power receptacle is in P715.

Characteristics

Each external power contactor has these properties:

- Conducts three phase ac

- Can operate at 260 amperes continuous and 350

amperes for 15 seconds

- Can open 2000 amperes

- Uses 28 volts dc for control

- Electrically held closed

- Spring loaded open.

Operation

The contactor closes when the BCU energizes the coils

of the contactor with 28 volts dc. After the contactor

closes, contacts remove power from one of the two

coils. This is because less power is necessary to hold

the contactor closed than to initially close it. This

decreases the power necessary to keep the contactor

closed.

The contactor opens when the BCU removes the coil

power. This lets the spring open the contactor.

ELECT PWR -- AC EXT POWER - POWER CONTACTORS

- 26 -



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ELECT PWR - AC EXT POWER - POWER CONTACTORS

P714

A

B

C

A

B

C

CLOSE AND

SPRING

P715HOLD INPUT28V DC

- 27 -



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General

There are two bus control units (BCU) in the MEC on the

E-1 and E-2 equipment shelves. They operate on 28 volt

dc. The units are the same and inter-changeable. The

BCUs monitor their related external power and APU power

channels and the airplane electrical system to give

control and protection. Circuit breakers on the front

panel give the internal circuits protection from shorts

on control and indication lines.

The BCUs control the XPCs, APBs and SSB. They are also

the primary communication link between the electrical

system and the EFIS/EICAS interface units (EIU).

Control Functions

Each BCU has these control functions:

- Ground power- APU interface signals

- APU generator interface

- APU generator field

- Auxiliary (APU) generator control unit (AGCU)

interface signals

- APB

- XPC

- SSB

- Anticycle and lockout functions- Master frequency reference

- No-break power transfer

- Ground service and ground handling bus

- Load management

- Autoland control (electrical system)

- DC and standby systems interface- Instrument bus voltage sensing unit (IBVSU)

interface

- System BITE

- Interface with the EIU and CMC.

Protection Functions

Each BCU has these protective functions:

- Ground power over/under voltage

- Ground power over/under frequency

- Ground power phase rotation

- Ground power plug fault

- Synch bus negative sequence voltage

- Synch bus differential fault

- Sustained unlike source protection

- CPU failure

- BCU power supply failure- APU generator bearing failure.

ELECT PWR -- AUTOMATIC CONTROL - BUS CONTROL UNITS

- 28 -

and GHR,GSTR,GSSR



747 TRAINING MANUAL

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ELECT PWR - AUTOMATIC CONTROL - BUS CONTROL UNITS

- CONTROL- PROTECTION

- 29 -



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747 TRAINING MANUAL


General

Two external power transformer rectifier units (TRU)

are in the forward left MEC at the station 400

bulkhead. They are TRU A and TRU B.

The TRUs are solid state devices that change 115 volts

ac to 28 volts dc. They keep the dc output up to a 20

ampere load. Both TRU A and TRU B get power from the

GHB. Each TRU supplies a separate dc GHB.

ELECT PWR -- AC EXT POWER - TRANSFORMER RECTIFIER UNITS

- 30 -

AC GHBTRU

TRU

DC GHB

DC GHB



747 TRAINING MANUAL

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ELECT PWR - AC EXT POWER - TRANSFORMER RECTIFIER UNITS

FWD

TRU (A)

TRU (B)

- 31 -



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747 TRAINING MANUAL


General

There are four ground service relays (GSR) in P714 in

the MEC. Each relay is a 3 pole, double throw type

relay and is inter-changeable with the others. BCU 1

energizes the relays to connect power for the ground

service bus. The three possible sources of ground

service power are:

- AC bus No. 1

- APU generator No. 1- External power No. 1.

ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE RELAYS

- 32 -

747 TRAINING MANUAL



747 TRAINING MANUAL

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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE RELAYS

P714

EXT 1

(4)

28V DC FROM

APU 1

PERMANENT

GSSR (2) GSTR (2)

28V DC FROM

GROUND

PERMANENT

AC 1MAGNET

BCU 1BCU 1

SERVICEBUS

MAGNET

- 33 -



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747 TRAINING MANUAL


General

The split system breaker (SSB) electrically connects

the left and right synch buses. It is in the P92 panel

in the MEC. The breaker is a magnetic latch type and

can operate at 450 amperes continuous. It can open up

to 5000 amperes. The breaker must get 28 volts dc to

close or to open. The control signals to the SSB come

from the BCUs. BCU 1 or BCU 2 can open the SSB. Only BCU

2 can close it. The SSB is not inter-changeable with

the other breakers on the airplane.

ELECT PWR -- MANUAL CONTROL - SPLIT SYSTEM BREAKER

- 34 -

747 TRAINING MANUAL



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ELECT PWR - MANUAL CONTROL - SPLIT SYSTEM BREAKER

P92

CLOSE28V DC

TRIP28V DC

COMMON

CLOSE (PERMANENT MAGNET)

- 35 -



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747 TRAINING MANUAL


General

You use the ground handling bus (GHB) for ground

operations. It can only get power on the ground. The

bus has two sections and can get power from external

power 1 or APU generator 1. BCU 1 controls the

connection of power to the GHB.

External Power

When there is external power at the aft external powerreceptacle, BCU 1 monitors the average of all three

phases for these:

- Voltage (104.5 to 125v ac)

- Frequency (375 to 425 hz)

- Phase rotation (A B C)

- No overcurrent or overvoltage on pins E and F (this

can occur if the external power plug had damage and

there was a short between the main ac voltage andpins E or F)

- Pin E/F connected (this makes sure that the

external power plug is fully in).

After BCU 1 finds these conditions, it gives an

external power available signal. At this time, these

conditions can keep external power off the GHB:

- Airmode (BCU 1 gets data that three IDGs are above6100 rpm)

- GHR has a failure (BCU 1 monitors for a short to

ground on the control wire to the GHRs. If itsenses a short, the BCU removes the close command

to the relay).

If the conditions for input power are true, and the

inhibit conditions are not true, the BCU energizes the

two GHRs. The GHB then gets external power.

APU Power

The auxiliary generator control unit (AGCU) monitors

power from APU generator 1. When the APU is above 95

percent, and the voltage is between 104 and 130v ac,

the AGCU sends an APU power ready signal to the BCU. If

external power is not available, and the inhibit

conditions are not true, APU generator 1 gives power to

the GHB.

ELECT PWR -- AC PWR DISTRIBUTION - GROUND HANDLING BUS CONTROL

- 36 -

747 TRAINING MANUAL



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ELECT PWR - AC PWR DISTRIBUTION - GROUND HANDLING BUS CONTROL

PIN E/F

AIR MODE

BAT SW

HOT BAT BUS

DC GHB

BCU STBY

R117 GHR 1

R118 GHR 2

TO APB

MAIN BATTERY

AC

NOT IN

PHASE

VOLTS/FREQ

NO FAULTS ON

POWER LOGIC

F

E

N

C

BA

TO

BCU 1

TO

GSTRXPCR284 GND

G

A

APU RPM >95%

APU GEN 1AGCU 1

GHB

TRU TRU GHB

EXT PWRAVAILABLE

GHR FAILED

APU POWERREADY

USE

CONN

PWR RECEPTACLE 1(AFT) (P36)

INTERLOCK

ROTATION OK

OK

BUS

(APU-BCU 1)

(MAIN-BCU 2)

SAFETY(P414)

(P714)

(P714)

SECT 1

SECT 2

INTERNALCIRCUITS

XPC

PWR XFRRLY (P414)

A B

CONNECTED

W

W

B

A

TRU

B

VOLTS OK

A

- 37 -



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747 TRAINING MANUAL


General

Power for the ground service bus (GSB) comes from AC 1

if AC 1 has power. If AC 1 does not have power, power

for the GSB is selected by a push of the ground

services switch on the attendants panel at door 2L.

This connects power from either external or APU

sources. The external source has priority. When GSB

power is from a selected source, a light in the ground

services switch on the attendants panel comes on.

ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS POWERELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS POWER

- 38 -

747 TRAINING MANUAL



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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE BUS POWER

GSB

ATTENDANTS PANEL

LIGHTS/CHIME

FORWARD

CHIME OFF

AFT

CHIME OFF

LIGHT

WORK

LIGHT

GROUND

LIGHTS

EMERGENCY

ACCESS

UPPER DECK

w w w w

rw w w

OVERSTAIR

THRESHOLD

DOOR 2L

SERVICESLIGHT

- 39 -



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747 TRAINING MANUAL



ELECT PWR -- AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL

- 40 -



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General

The ground service bus (GSB) is for ground and flight

operations. The GSB has two buses. They are the GSB and

the ground service utility bus. The control logic is

the same for the two buses. Power for the ground

service utility bus goes through the energized contacts

of utility ELCU 1 before it goes to the transfer relay.

The data that follows refers to the GSB and the ground

service utility bus unless it tells you differently.

There are three possible power sources for the GSB:

- AC bus 1

- External power 1

- APU generator 1.

Components

These components have a relation to the GSB:

- BCU 1 in MEC

- Ground service switch at the flight attendant

station, door 2 left

- Two ground service transfer relays (GSTR) in P714

in the MEC

- Two ground service select relays (GSSR) in P714 in

the MEC.

One of the two GSTRs is for the ground service bus and

the other for the ground service utility bus. When they

close, the relays connect the APU or external power to

the GSB. When they open, the relays connect ac 1 power

to the GSB.

One of the two GSSRs are for the ground service bus and

the other for the ground service utility bus. When they

close, the relays connect external power for the GSB

through the GSTRs. When they open, they connect APU

power.

AC Bus No. 1 Power

When ac 1 has power, the GSTR deenergizes. This lets ac

1 give power to the GSB. For the ground service utility

bus to get power from ac bus 1, the left utility switch

on the electrical system control panel must be on.

External Power

If ac 1 does not have power, you must push the groundservice switch to get ground service power. When the

conditions that follow are true, the BCU energizes the

GSTRs and GSSRs to let external power 1 give power to

the GSB:

- External power in limits

- GSSR or GSTR not failed (if the BCU finds a short

to ground on the control wire to the GSSR and GSTR,

it removes the close command to the relays).

NOTE: A reset is accomplished by cycling the ground

service switch.

- 41 -



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747 TRAINING MANUAL



APU Power

If ac 1 does not have power, you must push the ground

service switch to get ground service power. When the

conditions that follow are true, the BCU energizes the

GSTRs to let APU generator 1 give power to the GSB:

- External power not available (ground service uses

external power 1 if it is available)

- APU power in limits

- GSTR not failed (if the BCU finds a short to groundon the control wire to the GSSR, it removes the

close command to the relay).

NOTE: A reset is accomplished by cycling the ground

service switch.

- 42 -

747 TRAINING MANUAL



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ELECT PWR - AC PWR DISTRIBUTION - GROUND SERVICE BUS CONTROL

GSSR

GSTR

GSTR

GSTR FAULT

CYCLE GS

FAULT

FAULT

GSSR FAULT

EXT PWR RDY

28V DC

ON

GROUND SERVICE

FLIGHT ATTENDANT

AC 1

AIRMODE

GSSR

TRIP/CLOSE

AGCU 1

APU PWRBCU NO. 1

TO GHR(S)

EXT 1

APB

BTB

APU1

XPC

U-ELCU-1

BAT

POWERED

SWITCH

PANEL (DOOR 2 LEFT)

CHGR

READY

SWITCHTO RESET

SENSING

LOGIC

SENSING

DC GND HDLG BUS

AC 1

BATCHGR

GND SERV BUS

GND SERV UTIL BUS

- 43 -

747 TRAINING MANUAL



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747 TRAINING MANUAL


General

There are two external power contactors (XPCs) that

connect external power to the airplane synch bus. One

contactor is in P714, and one is in P715 in the MEC.

These are the components related to the XPCs:

- External power panel (P36)

- BCU 1

- BCU 2

- EXT PWR 1 switch- EXT PWR 2 switch.

Control

DC power for the BCUs comes from one of four power

sources. This lets the BCU operate and give control and

protection during all normal conditions of operation.

These are the sources:

- Three-phase ac from external power (an internal

TRU in the BCU makes this dc)

- Main battery bus

- DC ground handling bus

- APU hot battery bus with the battery switch on for

BCU 1 (BCU 2 uses the main hot battery bus with the

battery switch on).

The BCUs look at the external power and do a check forthese:

- Voltage (104.5 to 125v ac)

- Frequency (375 to 425 hz)

- Phase rotation (A B C)

- No faults on pins E or F (over current or overvoltage on these pins E and F give an indication of

a short in the power plug)

- Pin E and F connected (this makes sure that the

external power plug is fully in).

When the above conditions are true, the BCUs cause the

external power AVAIL lights in the P5 external power

switches, the NOT IN USE, and the AC CONNECTED lights

to come on. The NOT IN USE light goes off when the XPCor GSTR closes.

These are the conditions necessary for the external

power close command:

- External power available

- No inputs from trip logic (These inputs open the

XPC for system protective trips, power transfers

and last source on logic)- A close command from the external power switch and

not in air mode (There is a 4.5 second interval if

there was a close command before this one).

When these conditions are true, the BCU sends an

external power close command to the no break power

transfer logic. This logic sends the close command to

the XPC. When the XPC closes, these things occur:

- Sync bus gets three-phase, 400 hz ac

- External power ON light comes on

- AVAIL light goes off

- NOT IN USE light on P36 goes off.

ELECT PWR -- EXT POWER - CONTACTOR CONTROL

- 44 -

747 TRAINING MANUAL



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ELECT PWR - EXT POWER - CONTACTOR CONTROL

DC GHB

SYNCH

PIN E/F

TRIP LOGIC

AC

XPCGSTR

EXT PWR AVAIL

PHASE

VOLTS/FREQ

TRU

TO INTERNAL

MAIN

EXT POWER

F

E

N

C

B

A

EXT PWR AVAIL

BCU 1

TRIP/CLOSE

NOT IN

NO FAULTS ON

AIR

EXT PWR

EXT

ELECTRICAL SYSTEM

NO BREAKXPC

POWER LOGIC

BCU STBY PWR

HOT BAT BUS

BAT SW

AV

ILw

w

ONA

BATTERYBUS

XFR RLY (P414)

(APU-BCU 1)(MAIN-BCU 2)

CONTROL PANEL (P5)

PWRON

USE

CONN

(P36)

NOTE: SYSTEM 1 SHOWN SYSTEM 2 SIMILAR

LOGIC(4.5 SEC TD)

POWERTRANSFER

BUS

CIRCUITS

OK

ROTATION OK

INTERLOCK

CONNECTED

CLOSECOMMAND

MODE

W

W

RECEPTACLE 1

EXT PWR 1

- 45 -

747 TRAINING MANUAL



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747 TRAINING MANUAL


Manual Operation

The SSB control switch manually controls the split

system breaker (SSB). The switch is a momentary type

with a guard. It is on the generator manual reset panel

in the flight deck. Each operation of the switch

changes the position of the SSB from open to closed or

closed to open. The switch does not cause operation of

the SSB when the BCUs are in air mode or there are

sources on each side of the synch bus that cannot

connect together.

If there is IDG power on both sides of the synch bus,

you can manually open the SSB with the SSB control

switch. If you operate the switch again, the SSB does

not close until an auto parallel sequence is done.

SSB Close

The SSB automatically closes for these conditions:

- First source on the synch bus

- A close command from BCU 1 (a close signal from BCU

1 goes to BCU 2 and BCU 2 closes the SSB)

- IDG power is on each side of the synch bus, and

parallel conditions and a 300 MS time delay is true

- One side of the synch bus loses power after each

side had power (not as a result of a synch bus

malfunction, break power transfer, or the SSBcontrol switch).

The close signal goes to the SSB through the usually

closed contacts of the SSB protection relay.

SSB Trip

The SSB automatically opens for:

- No break power transfer (NBPT) logic under some

electrical system configurations

- Sources on each side of the synch bus that cannot

connect together

- Loss of power to the opposite BCU (loss of

protection to one side of the synch bus)

- A negative sequence or differential fault on thesynch bus.

A negative sequence or differential fault resets for

these conditions:

- IDG power on each side of the synch bus and auto

parallel conditions are true

- Operation of the SSB switch

- Power removed from the airplane (the first sourceon resets the fault).

Indication

A light below the SSB control switch shows SSB

position. The light is on when the SSB is open. The

light gets power through a set of auxiliary contacts in

the SSB.

ELECT PWR -- EXT POWER - SPLIT SYSTEM BREAKER CONTROL

- 46 -

747 TRAINING MANUAL



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ELECT PWR - EXT POWER - SPLIT SYSTEM BREAKER CONTROL

300 MS

BPT LOGIC

FIRST SOURCE ON SYNCH BUS

CLOSE COMMAND (BCU 1)

POWER ON BOTH SIDES

S

CLOSE

OPEN

R

AUTO PARALLEL COMPLETE

IDG POWER ON BOTH

EXT/APU/UNLIKE POWER ON

EXT/APU/UNLIKE POWER ON

FIRST SOURCE ON SYNCH BUS

AUTO PARALLEL COMPLETE

OPP BCU SYNCH BUS FAULTS

LOGICTRIP/CLOSE

AIRMODE

SR

SYNCH BUS FAULTS

TRIP

CLOSEOS

OS

IDG POWER ON BOTH

S R

NBPT LOGIC

OPPOSITE BCU NOT POWERED

SYNCH BUS FAULTS

AIRMODE

CYCLE SSB SW

AIRMODE

SSB (P92)

BCU 2 (E2-2)

SPLIT SYSTEM

OPEN

SSB CONT SW

CLOSE

OPEN

FROM

R8128 SSB

SIDES OF SYNCH BUS

OF SYNCH BUS

TD

BOTH SIDES OF SYNCH BUS

SIDES OF SYNCH BUS

BOTH SIDES OF SYNCH BUS

AUXCON-TACTS

PROTECTION(P92)

BCU 1

(P461)

BREAKER

A

A

- 47 -

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747 TRAINING MANUAL


General

The electrical system can do no break power transfers

(NBPTs). A NBPT is a change of an ac power source

without a break in power. To do this, power sources

momentarily operate in parallel. All power transfers

between engine generators, APU generators and external

power are no break power transfers. The only time power

breaks occur are when two external power sources or two

APU generators connect to an airplane that has no other

electrical sources connected. If all buses get powerfrom one external power source and you connect the

second external source, the SSB opens before the second

XPC closes. This causes a momentary break in power. If

all buses get power from an APU generator and you

connect the second APU generator, there is also a

momentary break in power. The two BCUs have the primary

control for NBPT.

Power Configurations

Before you connect EXT power to the airplane, the NBPT

logic in the BCUs finds the power configuration of the

synch bus. These are the seven possible power

configurations of the synch bus:

- No power

- Adjacent APU generator

- Adjacent IDG- Opposite APU generator with SSB closed

- Opposite IDG with SSB closed

- Adjacent and opposite IDG

- Opposite external power with SSB closed.

ELECT PWR -- EXT POWER - NO BREAK POWER TRANSFER

- 48 -

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ELECT PWR - EXT POWER - NO BREAK POWER TRANSFER

EXTERNAL

NO POWER

OPPOSITE APU

OPPOSITE

SSB

SYNCH BUS POWER

NO BREAK POWER

POWER INTERRUPT

ADJACENT IDG

OPPOSITE IDG

ADJACENT

ADJ AND OPP

APU GENERATORPOWER

CLOSED

GENERATOR

IDG

EXTERNAL POWER

TRANSFER

- 49 -

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General

When the no break power transfer logic in BCU 1 senses

no power on the synch bus and an external power close

command, it closes its XPC and sends a signal to BCU 2

to close the SSB. If the close command goes to BCU 2

with a dead synch bus, BCU 2 closes its XPC and the SSB.

BCU 1 and BCU 2 can open the SSB, but only BCU 2 can

close it.

ELECT PWR -- EXT POWER - NBPT - DEAD SYNCH BUS

- 50 -

747 TRAINING MANUAL



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ELECT PWR - EXT POWER - NBPT - DEAD SYNCH BUS

NO BREAK POWERCLOSE

XPC

SSB

BCU 2BCU 1 (E1-2)

CLOSEEXT PWR 1

POWER ON ADJ

SSB

CLOSECOMMAND

SYNCH BUS

TRANSFER LOGIC

LOGIC

- 51 -

747 TRAINING MANUAL



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General

If the synch bus has power from an APU generator and

you connect power from an adjacent external source, the

no break power transfer (NBPT) logic momentarily

connects the two sources in parallel. The adjacent APB

then opens to remove the APU generator power from the

synch bus.

Operation

Before the NBPT logic in the BCU connects the two power

sources in parallel, a comparator circuit compares

voltage, frequency and phase between the synch bus

power and the external power. Differences must be less

than:

- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

If there is a frequency difference of more than 3 Hz,

the BCU gives a speed command to the APU controller

(APUC). This increases or decreases the APU speed. All

speed signals that go to the APUC go through BCU 1.

When the voltage, frequency and phase are in limits,

the XPC closes. The BCU senses the position of the XPC

through a set of auxiliary contacts in the XPC. Afterthe XPC closes, the BCU opens the APB. The power on the

synch bus now comes from the external source.

The BCU has a 6 second time delay that becomes active

when the close command signal goes to the BCU. This

time delay causes the APB to open if voltage, frequency

and phase are not in limits after 6 seconds. After this

time delay the APB opens and removes power from the

synch bus, and the XPC closes. This causes a momentary

break in power. When the XPC closes, the 6 second time

delay resets.

Sustained Unlike Source Protection

Sustained unlike source protection (SUSP) is a

protection circuit in the BCU. Its primary function is

to put a maximum limit on the time (110 ms) that two

power sources of different types are in parallel. SUSP

starts when the XPC closes. It resets when the APB

opens. If the APB does not open in the time limit, the

SUSP opens the APB and the XPC. This removes the two

sources from the sync bus. After a SUSP trip you must

connect the necessary power source again.

ELECT PWR -- EXT POWER - NBPT - ADJACENT APU

- 52 -

747 TRAINING MANUAL



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ELECT PWR - EXT POWER - NBPT - ADJACENT APU

6

SUSP TRIP

SUSP RESET

APBTRIP

TRIP

TRIPSPEED

POWER ON ADJ

V/F/PHASE

BCU

XPC CLOSEDXPC

EXT PWR

POWER ON

RESET

TRIP

ADJ APB

EXT PWR

SUSP XPC CLOSED

TD

SYNCH BUS

CLOSED

CLOSECOMMAND

COMMANDTO APUC

SYNCH BUS

COMPARATOR

110 MS LOGIC

- 53 -

if the XPC fails to close in 6 second,theTD outlet a trip discrete to trip APB.AfterAPB triping,the XPC closes.

if APB fails to open in 110 ms after XPCclosing,the SUSP output a trip discrete to tripXPC and APB simultaneously.

the SUSP provides a tiime-limit for maximumperiod different type sources are in parallel.

for increasing or decreasing the

speed of APU .In order tosynchronize the voltage,frequencyand phase .

747 TRAINING MANUAL



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General

If the synch bus has power from an IDG and you connect

power from an adjacent external source, the no break

power transfer (NBPT) logic momentarily connects the

two sources in parallel. The adjacent GCB then opens to

remove the IDG power from the synch bus. If there are

two IDGs in operation, they operate the same.

Operation




power and the APU power. Differences must be less than:

- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

The BCU monitors external power C phase frequency and

sends this data as a digital reference frequency to the

GCU. The GCU increases or decreases IDG speed until the

difference between the frequency of IDG and external

power is in limits. When the voltage, frequency and

phase are in limits, the XPC closes. The BCU senses the

position of the XPC through a set of auxiliary contacts

in the XPC. After the XPC closes, the BCU sends an open

signal on the digital data bus to the GCU. The GCUopens the GCB if the BTB is closed. If the BTB is open,

the GCB stays closed. The power on the synch bus now

comes from the external source.



time delay causes the BCU to send a trip signal to the

GCU over the digital data bus if voltage, frequency and

phase are not in limits after 6 seconds. After this

time delay the GCU opens the GCB and removes power from

the synch bus. The XPC then closes. This causes a

momentary break in power. When the XPC closes, the 6

second time delay resets.



protective circuit in the BCU. Its primary function is



starts when the XPC closes. It resets when IDG power is

no longer on the adjacent synch bus. If the GCB does

not open in the time limit, the SUSP sends a trip

signal over the digital data bus to the GCU. The GCU

opens the BTB on IDGs where the GCB did not open.

ELECT PWR -- EXT POWER - NBPT - ADJACENT IDG

- 54 -

747 TRAINING MANUAL



24-40-00

2 4 - 4 0 - 0 0 - 0 0 9

R e

v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - EXT POWER - NBPT - ADJACENT IDG

6

NOTE: TYPICAL OF BCU AND 2 ADJACENT IDG CHANNELS

POWER ON ADJ

V/F/PHASE

GCU

BCU

BTBGCB

TRIPTRIP

BTBGCB

TRIP

SUSP TRIP

XPC CLOSEDXPC

CLOSE XPC

EXT PWR C PHASE

EXT PWR

POWER ON

RESET

TRIP

SUSP RESET WITH NO IDG

ADJ BTB AND

EXT PWR

SUSP XPC CLOSED

POWER ON ADJ SYNCH BUS

SYNCH BUS

GCB CLOSED

CLOSECOMMAND

REF FREQ TO GCU(S)

SYNCH BUS

COMPARATOR

TD LOGIC LOGIC

LOGIC110 MS

- 55 -

for increasing or decreasing theIDG speed .In order to

synchronize thevoltage,frequency and phase .

trip the BTB where theGCB didn't open.

trip the GCB where

the BTB is closed.

747 TRAINING MANUAL

ELECT PWR EXT POWER NBPT OPPOSITE APU



24-40-00 2 4 - 4 0 - 0 0 - 0 1 0

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1 0 / 2 8 / 1 9 9 9


General

If the synch bus has power from an APU generator and

you connect power from an opposite external source, the

no break power transfer (NBPT) logic momentarily

connects the two sources in parallel. If the two

external power sources are available, the SSB opens. If

only one external power is available, the opposite APB

opens.

Operation





than:

- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

If there is a frequency difference of more than 3 Hz,

the BCU gives a speed command to the APU controller

(APUC). This increases or decreases the APU speed. All

speed signals that go to the APUC go through BCU 1.



through a set of auxiliary contacts in the XPC. After

the XPC closes, the BCU opens the SSB or the APB. If the

two external power sources are available the SSB opens.

If only one external power source is available, the

opposite APB opens.



time delay causes the SSB or APB to open if voltage,

frequency and phase are not in limits after 6 seconds.

This removes power from the synch bus, and the XPC

closes. This causes a momentary break in power. When

the XPC closes, the 6 second time delay resets.






starts when the XPC closes. It resets when APU power is

no longer on the adjacent synch bus. If the APB (one

external source available) or SSB (two external sources

available) does not open in the time limit, the SUSP

opens the XPC and the APB. This removes the two sources

from the sync bus. After a SUSP trip you must connect

the necessary power source again.

ELECT PWR -- EXT POWER - NBPT - OPPOSITE APU

- 56 -

if the two external power sources and the two APU powersources are used, After pressing in the external powerswitch,the adjacent APB and SSB open. After pressing inthe opposite external power switch,the SSB stays opened

and opposite APB opens.

747 TRAINING MANUAL



24-40-00

2 4 - 4 0 - 0 0 - 0 1 0

R e

v

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1 0 / 2 8 / 1 9 9 9


ELECT PWR - EXT POWER - NBPT - OPPOSITE APU

6TRIP

SSB

SUSP

BOTH EXT

APB

XPC CLOSED

XPC

TRIP

RESET

V/F/PHASE

SPEED

BCU

EXT PWR

POWER ONTRIP

CLOSE XPC

SUSP

OPP APB

SSB

TRIP

EXT PWR

POWER ON ADJ

SUSP RESET WITH NO APU

XPC CLOSED

TD

SYNCH BUS

CLOSED

CLOSED

CLOSECOMMAND

COMMANDTO APUC

SYNCH BUS

COMPARATOR

POWER ON ADJ SYNCH BUS

PWR AVAILABLE

110 MS

LOGIC

TRIP

- 57 -

747 TRAINING MANUAL

ELECT PWR -- EXT POWER - NBPT - OPPOSITE IDG



24-40-00 2 4 - 4 0 - 0 0 - 0 1 1

R e v

1

1 0 / 2 8 / 1 9 9 9


General

If the synch bus has power from an IDG and you connectpower from an opposite external power source, the no

break power transfer (NBPT) logic momentarily connects

the two sources in parallel. If the two external power

sources are available, the SSB opens. If only one

external power source is available, the opposite GCB

opens. If there are two IDGs in operation, they operate

the same.

Operation





than:

- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

The BCU monitors external power C phase frequency and

sends this data as a digital reference frequency to the

GCU. The GCU increases or decreases IDG speed until the

difference between the frequency of IDG and APU power C

phase power is in limits.



through a set of auxiliary contacts in the XPC. After

the XPC closes, the BCU then finds if opposite external

power is available. If the opposite external power is

available, then the SSB opens. If the opposite external

power is not available, then the GCB opens.



time delay causes the SSB or GCB to open if voltage,

frequency and phase are not in limits after 6 seconds.

After this time delay the SSB opens if two external

power sources are available, or the GCB opens if only

one external power source is available. This removes

power from the synch bus, and the XPC closes. This

causes a momentary break in power. When the XPC closes,

the 6 second time delay resets.






starts when the XPC closes. It resets when IDG power is

no longer on the adjacent synch bus. If the SSB or GCB

does not open in the time limit, the SUSP sends a trip



ELECT PWR EXT POWER NBPT OPPOSITE IDG

- 58 -

external

747 TRAINING MANUAL



24-40-00

2 4 - 4 0 - 0 0 - 0 1 1

R e

v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - EXT POWER - NBPT - OPPOSITE IDG

6

XPC CLOSED

EXT PWR

SSB

XPC CLOSED

SUSP TRIP

POWER ON ADJ

OPP BTB AND

TRIP

RESET

POWER ON

EXT PWR

BCU

V/F/PHASE

EXT PWR C PHASE

CLOSE

BTBGCB

TRIPTRIP

GCU

OPEN

SUSP

OPP EXT

SUSP RESET WITH

SYNCH BUS

GCB CLOSED

CLOSED

CLOSECOMMAND

REF FREQ TO GCU(S)

SYNCH BUS

NO IDG POWER ONADJ SYNCH BUS

PWR AVAIL

LOGIC

COMPARATOR

TD

XPC SSB

LOGIC LOGIC

110 MS

XPC SSB GCB BTB

- 59 -



747 TRAINING MANUAL

ELECT PWR -- EXT POWER - NBPT - ADJACENT AND OPPOSITE IDG



24-40-00 2 4 - 4 0 - 0 0 - 0 1 3

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- 62 -

747 TRAINING MANUAL

CLOSEOPENSSB

SSBOPENED

XPCCLOSEDXPC



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v

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1 0 / 2 8 / 1 9 9 9


ELECT PWR - EXT POWER - NBPT - ADJACENT AND OPPOSITE IDG

6

SUSP

RESET

SUSP RESET WITH

BCU

EXT PWR

ANY OPP

ANY ADJ

OPP EXTTO ALL

TO ADJ GCU(S)

TO ALL GCU(S)

OPP EXT

EXT PWR C PHASE

EXT PWR

POWER ON

V/F/PHASE TRIP

TRIP

XPC

GCB ANDBTB CLOSED

GCB ANDBTB CLOSED

CLOSEDCOMMAND

PWR AVAIL

COMPARATOR

SYNCH BUS

NO IDG POWER ONADJ SYNCH BUS

110 MS

CLOSEDLOGIC

PWR AVAILFOUR GCU(S)

TO TRIPGCB(S)

TO TRIP GCB(S)

FOR BTB SUSP TRIPREF FREQ TO GCU(S)

TD

SSB XPC

- 63 -

747 TRAINING MANUAL

ELECT PWR -- EXT POWER - NBPT - OPPOSITE EXTERNAL POWER



24-40-00 2 4 - 4 0 - 0 0 - 0 1 2

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General

If the synch bus has power from the opposite externalpower source and you connect power from the adjacent

external power source, the system does not use the no

break power transfer (NBPT) logic. When the BCU gets

the external power close command, it opens the SSB.

This causes a momentary break in power. When the BCU

senses that the SSB is open, it closes the XPC. The BCU

monitors SSB position through the auxiliary contacts in

the SSB.

- 64 -

747 TRAINING MANUAL



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2 4 - 4 0 - 0 0 - 0 1 2

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ELECT PWR - EXT POWER - NBPT - OPPOSITE EXTERNAL POWER

BCU

TRIP

CLOSE

SSB OPEN

CLOSE XPC

OPPOSITE XPC

POWER ON ADJ

SSB CLOSED

EXTERNAL POWER

SYNCH BUS

CLOSED

CLOSE COMMAND

ADJ XPC

SSB

XPC

- 65 -

747 TRAINING MANUAL

G l

ELECT PWR -- AC GENERATION - APU POWER SOURCES



24-20-00 2 4 - 2 0 - 0 0 - 0 0 1

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General

The airplane can use the two APU power sources while onthe ground.

The two APU generators on the APU load gearbox supply

400 Hz, 3 phase, 115 volts ac and can supply a maximum

of 90 kva. The generator feeders are AWG 0 copper in

the APU compartment and have a splice to AWG 00

aluminum forward of the APU firewall. The AWG 00

aluminum feeders go to the main equipment center. They

connect at their related auxiliary power breakers (APB)in P714 and P715.

- 66 -

747 TRAINING MANUAL



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2 4 - 2 0 - 0 0 - 0 0 1

R

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ELECT PWR - AC GENERATION - APU POWER SOURCES

APU DRIVEN

APU GENERATOR

P714

P715

GENERATORS

FEEDERS

- 67 -

747 TRAINING MANUAL

General

ELECT PWR -- AC GENERATION - APU POWER COMPONENTS



24-20-00 2 4 - 2 0 - 0 0 - 0 0 2

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General

The APU power system components are in the MEC, flightdeck and in the APU compartment in the tail. The APU

power system includes:

- APU generators (2)


- Electrical system control panel

- Current transformers (5)

- Auxiliary power breakers (2)

- Bus control units (2)- Auxiliary generator control units (2).

- 68 -

747 TRAINING MANUAL

4321

GEN FIELD MAN RESET



24-20-00

2 4 - 2 0 - 0 0 - 0 0 2

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ELECT PWR - AC GENERATION - APU POWER COMPONENTS

GENERATOR MANUAL

QAD RINGS

AUXILIARY GENERATOR

ELECTRICAL SYSTEM

AUXILIARY POWER

BUS CONTROL UNITS

CURRENT

APU GENERATORS

ww

ww

w

w

21

w

FIELDOFF

FIELD

OFFFIELD

OFFFIELD

OFF OFFFIELD

OPEN

BREAKERSPLIT SYSTEM

APU

OFFFIELD

RESET PANEL (P461)

CONTROL UNITS

BREAKERS

TRANSFORMERS

CONTROL PANEL (P5)

- 69 -

747 TRAINING MANUAL

General close its related auxiliary power breaker (APB). The ON

ELECT PWR -- AC GENERATION - APU POWER GENERAL OPERATION



24-20-00 2 4 - 2 0 - 0 0 - 0 0 3

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General

Two APU generators supply three-phase, 400 Hz ac powerto the airplane. Before the power connects to the

airplane systems, two auxiliary generator control units

(AGCU) monitor the power to make sure that it is at the

correct voltage and frequency. When the AGCUs find that

the power is good, they send a signal to the BCUs to

turn on the two APU generator AVAIL lights on the

electrical system control panel in the flight deck.

Ground Handling Bus

When BCU 1 turns on the APU generator AVAIL light, it

also energizes the ground handling relay (GHR) to give

power to the ground handling bus (GHB). Cargo loading,

cleaning outlets and fuel are some of the systems on

the GHB.

Ground Service Bus

The ground service switch is at the flight attendant

panel at door 2L. When you push this switch, BCU 1

energizes the ground service relays to give APU power

to the ground service bus (GSB). APU power does not

connect to the GSB if ac bus 1 has power or external

power 1 is available.

APU Power

The two momentary switches, APU GEN 1 and APU GEN 2,

are on the electrical system control panel. When you

push APU GEN 1, BCU 1 sends a close signal to AGCU 1 to

close its related auxiliary power breaker (APB). The ON

light in the switch comes on and the AVAIL light goes

off. BCU 2 closes the SSB at this time if no other poweris on the synch bus. APU GEN 1 now supplies power to the

airplane. When you push APU GEN 2, BCU 2 opens the SSB

then sends a close signal to AGCU 2 to close its

related APB. The ON light in the switch comes on and

the AVAIL light goes off. APU GEN 1 now supplies power

to the left side of the synch bus and APU GEN 2 supplies

power to the right.

If you push the APU GEN switch with the APB closed, theBCU sends an open command to the AGCU and APB. The AGCU

then also sends an open command to the APB. This makes

sure that the APB opens.

The BCU or AGCU can open the APB for electrical

malfunctions.

- 70 -

747 TRAINING MANUAL

STANDBY POWER

OFFAUTO

BAT

L - UTILITY - R

OFF

ONw

aOFF

ONw

a

APU

ONOFF START



24-20-00

2 4 - 2 0 - 0 0 - 0 0 3

R

e v

1

0 7 / 2 5 / 2 0 0 1


FAULT TRIP/FAULT TRIP/

GROUND

APU GEN 1 APU GEN 2

AUX PWR

GROUND

GHB

GSB

AGCUSSB

TRIP

TRIP

AGCU

CLOSESSB

APBAPB

wAUTO BUSw

AUTOw

AUTOw

AUTO

EXT PWR 1 APU GEN 1

ON

BATTERY

w w

AVAIL

OFF

ONw

aON

w

AVAIL

ON

w w

AVAIL

ON

w

AVAIL

APU GEN 2 EXT PWR 2

APBAPB

FAULT TRIP

BCU 1 BCU 2

FAULT TRIP

SYNCH

OPEN/CLOSE

OPEN/CLOSE

OPEN/CLOSE

OPEN/CLOSE

OPEN/CLOSE

OK

OPEN

SERVICE

OPEN/CLOSE

OPEN

CLOSE

BUSSYNCHBUS

SELECTEDSERVICE

ELECT PWR - AC GENERATION - APU POWER GENERAL OPERATION

- 71 -

747 TRAINING MANUAL

General dc goes to the field of the main generator. The main

ELECT PWR -- AC PWR GEN AND PROTECTION - APU GENERATORS



24-21-00 2 4 - 2 1 - 0 0 - 0 0 1

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There are two inter-changeable generators on theforward face of the APU load gearbox. Each generator

supplies the airplane on the ground with ac power up to

90 kva. The generator contains three generators in one:

- Permanent magnet generator (PMG)

- Exciter generator

- Main generator.

Characteristics

Bendix makes the APU generators. The generators have

these properties:

- Weight, 68 lbs

- Rated voltage (line-to-neutral), 120 volts ac

- Rated voltage (line-to-line), 208 volts ac

- Phase, 3

- Frequency, 375-425 Hz- Rated speed, 7600-8400 rpm

- Rated load (continuous), 90 kva

Operation

There are six permanent magnets attached to the rotor

shaft. These supply three phase, 80 volts ac (at zero

load). The AGCU changes the voltage to dc, controls it,

and sends it back to the generator exciter field. Thearmature of the exciter generator supplies three phase

ac to the field of the main generator. Three diodes

turn with the field and change the voltage to dc. This

generator supplies three phase, 400 Hz, 120/208 volts

ac.

There is a current transformer on each phase of the

ground side of the main generator leads. These current

transformers monitor for differential protection and

total current output of the generator.

- 72 -

747 TRAINING MANUAL

CURRENT



24-21-00

2 4 - 2 1 - 0 0 - 0 0 1 R

e v

1

1 0 / 2 6 / 1 9 9 9


ELECT PWR - AC PWR GEN AND PROTECTION - APU GENERATORS

3 PHASE

3 PHASE

DIFFERENTIAL

DC

MAIN

EXCITERPMG

AGCU

QAD RING

TERMINAL

CURRENTTRANSFORMERASSEMBLY

BLOCK

400 HZPROTECTIONCURRENTTRANSFORMERS

GENERATOR

GENERATOR

80V AC

115/200V

- 73 -

747 TRAINING MANUAL

General

ELECT PWR -- AC PWR GEN AND PROTECTION - APU GENERATOR INSTALLATION



24-21-00 2 4 - 2 1 - 0 0 - 0 0 2

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1

1 0 / 2 6 / 1 9 9 9


Each APU generator attaches to the APU load gearboxwith a quick attach detach (QAD) ring or clamp. An

adapter plate attaches to the gearbox pad with machine

screws. The QAD ring pulls the generator toward the

plate as you tighten the ring. This is because of the

slope of the surface on the ring and adapter plate.

Before you install the generator, you must put on a new

lubricated O-ring. Be careful to make sure that the

index pin correctly engages with the generator indexpin hole before you torque the ring. It is possible to

install the QAD ring and not have the index pin in the

hole.

- 74 -

747 TRAINING MANUAL



24-21-00

2 4 - 2 1 - 0 0 - 0 0 2 R

e v

1

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ELECT PWR - AC PWR GEN AND PROTECTION - APU GENERATOR INSTALLATION

1

3

2

N

QAD RING

QUICK

INDEX PIN

APU O-RING

TERMINAL

ADAPTER

APU LOAD

GENERATOR

PLATE

GEARBOX

ATTACH-DETACHMOUNTING DEVICE

APU LOAD GEAR-BOXBLOCK

- 75 -

747 TRAINING MANUAL

General WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT

CONNECTION WITH THE FEEDER LINES POWERED THE

ELECT PWR -- AUTOMATIC CONTROL - APU POWER CURRENT TRANSFORMERS



24-23-00 2 4 - 2 3 - 0 0 - 0 0 2

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1

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The current transformers (CT) related to APU power arein P714 and in P715. The CTs have these functions:

- Metering (data sent to the BCUs for percent load

indications on EICAS, Sundstrand CTs)

- Load reduction (data sent to the BCUs for load

reduction circuits, Sundstrand CTs)

- Differential fault protection (data used by the

AGCUs, Bendix CTs)

In addition each APU generator has one CT in the

generator for differential fault protection.

Characteristics

There are two different types of CTs related to the APU

power system. Sundstrand makes one and Bendix makes the

other. Each transformer assembly has a toroidal shaped

core with secondary winding wires that connect to anoutput connector. Main ac feeder lines goes through the

large holes in the transformer and are the primary

winding for each transformer core. The turns ratio of

all of the windings of the Sundstrand transformers is

1000 to 1. The Bendix CTs are 500 to 1. If the primary

winding (feeder line) is 115 volts ac, secondary

winding voltage is as much as 115,000 volts with the

connector off (no load). Usually secondary voltages are

very low because the secondary loads have a lowresistance.


POTENTIALLY HIGH VOLTAGES COULD DAMAGE THETRANSFORMER OR RESULT IN INJURY TO PERSONNEL.

- 76 -



747 TRAINING MANUAL

General

ELECT PWR -- AC PWR GEN AND PROTECTION - AUXILIARY POWER BREAKERS



24-21-00 2 4 - 2 1 - 0 0 - 0 0 3

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1

1 0 / 2 6 / 1 9 9 9


There are two auxiliary power breakers (APB) thatconnect APU power with the airplane synch bus. They are

in the MEC in P714 and P715. The breakers are a

magnetic latch type and can operate at 275 amperes

continuous or 350 amperes for 15 seconds. Each can open

at up to 5000 amperes. The breakers must get 28 volts

dc to close or to open. The control signals to the APBs

come from the BCUs and AGCUs. The APBs are inter-

changeable with all of the other generator circuit

breakers and bus tie breakers.

- 78 -

747 TRAINING MANUAL



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2 4 - 2 1 - 0 0 - 0 0 3

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ELECT PWR - AC PWR GEN AND PROTECTION - AUXILIARY POWER BREAKERS

COMMON

28V DCTRIP

CLOSE

28V DCCLOSE

P715

P714

(PERMANENT MAGNET)

- 79 -

747 TRAINING MANUAL

General

ELECT PWR -- AC PWR GEN AND PROTECTION - AUXILIARY GENERATOR CONTROL UNITS



24-21-00 2 4 - 2 1 - 0 0 - 0 0 4

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There are two auxiliary generator control units (AGCU)in the MEC on the E1 and E2 equipment racks. They have

functions as voltage regulators and interface units

between the BCUs, APU generators and APBs.

Control Functions

Each AGCU has these control functions:

- Generator field control and indication- APB control

- APU generator power ready

- Auto parallel

- Anti-cycle.

Protective Functions

Each AGCU has these protective functions:

- Underspeed

- Overvoltage

- Undervoltage

- Differential fault

- Overcurrent.

- 80 -

747 TRAINING MANUAL



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ELECT PWR - AC PWR GEN AND PROTECTION - AUXILIARY GENERATOR CONTROL UNITS


- 81 -

747 TRAINING MANUAL

General you operate the field switch again the GCR opens. A GCR

open signal can occur because of:

ELECT PWR -- AC PWR GEN AND PROTECTION - AGCU OPERATION



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The two auxiliary generator control units (AGCU) in theMEC have functions as voltage regulators, generator

controllers and interface units between the BCUs, APU

generators and APBs.

Voltage Regulation

The PMG supplies three-phase 80-volt ac to the AGCU. A

TRU changes this voltage to dc for use by internal

control circuits and the APB. PMG voltage goes to thegenerator control relay (GCR). With the GCR closed

three-phase ac goes to a field current regulator

circuit which changes it to dc pulses. This dc goes to

the exciter generator which supplies the main generator

field. The main generator supplies the three-phase, 400

Hz, 115 volts ac. A circuit in the AGCU senses the

voltage and controls the field current regulator to

keep the correct voltage output of the generator.

GCR Control

The GCR in the AGCU is a latch type relay with an open

and a close coil. Power from the generator output goes

through the GCR to the field current regulator. The

relay is open by internal protective circuits, the

flight deck fire switch and the BCU. You momentarily

operate the APU generator field switch on the generator

manual reset panel to close the GCR. Each operationchanges the position of the GCR. The trip/close logic

in the BCU sends a close signal to the AGCU, and if

there is no malfunction, the AGCU closes the GCR. If

- An under voltage not caused by under speed or GCR

open

- An over voltage

- Fire switch operation

- APU generator bearing malfunctions: 5-minute time

delay (Reset with field switch)

- APU generator field switch operation.

- 82 -

747 TRAINING MANUAL

TO APBT1

T2

T3

VOLTAGESENSING



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ELECT PWR - AC PWR GEN AND PROTECTION - AGCU OPERATION

5 MIN

GENERATOR MANUAL

APU GEN

PMGGCR

FIELD

CLOSE

TRU

AGCU

TRIP

UNDER SPEED

GCR TRIPPED

UNDER VOLTAGE

DIFF FAULT

FIRE SWITCH

OVER VOLTAGE

POWER

EXCITER

TRIP/CLOSE

BCU

MAIN

PRIMARY

AUX

S

CLOSE

TRIP

R

1

FIELDOFF W

NO. 1

BEARINGFAIL

BAT BUS

CONTACTS

RESET PANEL (P461)

LOGIC

CURRENTREGULATOR

- 83 -

747 TRAINING MANUAL

General

ELECT PWR -- AC GENERATION - APU GENERATOR AVAILABLE LIGHT



24-20-00 2 4 - 2 0 - 0 0 - 0 0 4

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The APU generator AVAIL lights are on the electricalsystem control panel in the flight deck. The two

lights, one for APU GEN 1 and one for APU GEN 2, show

when APU power is in limits for frequency and voltage

and the APB is open.

Operation

The AGCUs give a power ready signal when:

- APU speed is above 95 percent

- Voltage is 104 to 130 volts ac

- There are no trip signals to the GCR.

After the BCUs get the power ready signal, the power

available driver turns on the APU generator AVAIL

lights. R230 in P414 inhibits the lights when the

airplane is in flight.

- 84 -

747 TRAINING MANUAL

STANDBY POWER

OFFAUTO

BAT

L - UTILITY - R

ONw

ONw

APU

ONOFF START



24-20-00

2 4 - 2 0 - 0 0 - 0 0 4

R e v

1

1 0 / 2 2 / 1 9 9 9


ELECT PWR - AC GENERATION - APU GENERATOR AVAILABLE LIGHT

APU

VOLT

VOLT

GCR NOT

AGCU

APU

POWER AVAIL

GND

AIR

ELECTRICAL SYSTEM

ON

wIAVA

APU GEN

R230 AIR/

BCU

EXT PWR 1 APU GEN 1

ON

OFF

BATTERY

a

w w

AVAIL

OFFa

OFF

ONw

aON

w

AVAIL

ON

w

AVAIL

ON

w

AVAIL

APU GEN 2 EXT PWR 2

w

APB

SPEED>95%

>104+/-1.5

<130+/-3

TRIPPEDCLOSED

GND SAFETY(P414)

CONTROL PANEL (P5)

DRIVER

POWERREADY

w

w

- 85 -

747 TRAINING MANUAL

General When the APB closes, auxiliary contacts in the APB turn

on the APU GEN ON light. The light does not show when

ELECT PWR -- AC GENERATION - AUXILIARY POWER BREAKER CONTROL



24-20-00 2 4 - 2 0 - 0 0 - 0 0 5

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1

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Two auxiliary power breakers (APB) connect APUgenerator power to the airplane synch bus. They are in

P714 and P715 in the MEC. These components have a

relation to the control of the APBs:

- AGCUs (2), BCUs (2)

- APU generator switches (2), APB close protection

relays (2).

APB Close

Each time you push the momentary APU generator switch,

it causes an APB close or APB open command. The

trip/close logic ignores new switch commands until it

completes the last command (APB open or closed) or a

4.5 second time delay. The BCU gives an APB close

command if all of these conditions are true:

- trip/close logic gives a close command- opposite APB is open or closed for 3.5 seconds

- no air mode inhibit with any GCB closed

- power ready signal from the AGCU.

The close APB signal goes to the no break power

transfer and auto parallel logic. The BCU then closes

the APB close protection relay and sends an APB close

signal to the AGCU. When the AGCU finds that the

generator can parallel or the bus is dead, it closesthe APB.

the airplane is in flight.

APB Open

The BCU or AGCU can send signals to open the APB. The

AGCU opens the APB for:

- Underspeed

- GCR trip signal.

The BCU opens the APB for:

- Synch bus faults

- CPU failure (BCU internal failure)

- Sustained unlike source protection

- Trip logic (power transfer complete, last source

on, bearing failure)

- No APU power ready signal.

- 86 -

747 TRAINING MANUAL

AIR

GNDAPU GEN 1

ON

AVA

I

APB CLOSED



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ELECT PWR - AC GENERATION - AUXILIARY POWER BREAKER CONTROL

AIRMODE

T

RS

C

AIRIL w w

ELECT SYSTEM

TRIP/CLOSE

GCR TRIP

AGCU 1

CLOSE

R301 APB CLOSE

APB

TRIP

POWER

NOTE: SYSTEM 1 SHOWN,

TRIP

R229 AIR

UNDER SPEED

DEAD BUS

V/F/PHASE OK

CPU FAIL

TRIP LOGIC

SYNCH BUS FAULTAPU POWER READY

SUSP

NBPT

BCU 1

ANY GCB

CLOSEOPP APB CLSD 3.5 SEC

CONT PANEL (P5)

LOGIC

(4.5 SEC TD)

CLOSED

READY

APB

GROUND SAFETY(P414)

PROTECTION (P714)

SYSTEM 2 SIMILAR

APB

ANDAUTO PAR

- 87 -

747 TRAINING MANUAL

General

The electrical system can do no break power transfers

ELECT PWR -- AC GENERATION - APU POWER NO BREAK POWER TRANSFER



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The electrical system can do no break power transfers(NBPT). A NBPT is a change of an ac power source

without the momentary break in power. To do this power

sources momentarily operate in parallel. All power

transfers between engine generators, APU generators and

external power are no break power transfers. The only

time power breaks occur are when two external power

sources or two APU generators connect to an airplane

that has no other electrical sources connected. If all

buses get power from one external power source and youconnect the second external source, the SSB opens

before the second XPC closes. This causes a momentary

break in power. If all buses get power from an APU

generator and you connect the second APU generator,

there is also a momentary break in power. The two BCUs

have the primary control for NBPT.

Power Configurations

Before you connect APU power to the airplane, the NBPT

logic in the BCUs finds the power configuration of the

synch bus. The seven possible power configurations of

the synch bus are:

- Dead (no power)

- Adjacent external power

- Adjacent IDG

- Opposite external power with SSB closed- Opposite IDG with SSB closed

- Adjacent and opposite IDG

- Opposite APU generator with SSB closed.

- 88 -

747 TRAINING MANUAL

DEAD



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ELECT PWR - AC GENERATION - APU POWER NO BREAK POWER TRANSFER

OPPOSITE

SSB

NO BREAK POWER

POWER INTERRUPT

ADJACENT IDG

OPPOSITE IDG

ADJACENT

OPPOSITE

APU

SYNCH BUS POWER

ADJ AND OPP

POWER

CLOSED

EXTERNAL POWER

EXTERNAL POWER

IDG

APU GENERATOR

TRANSFER

- 89 -

747 TRAINING MANUAL

General

When the no break power transfer logic in BCU 1 sensesl APB d ith th h b

ELECT PWR -- AC GENERATION - APU POWER NBPT - DEAD SYNCH BUS



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When the no break power transfer logic in BCU 1 sensesa close APB command with no power on the synch bus, a

signal goes to the APB close protection relay, to the

AGCU and to BCU 2 to close the SSB. The AGCU does a

check to find that the adjacent synch bus does not have

power then closes the APB. There is now APU power on

the left and right synch bus.

- 90 -

747 TRAINING MANUAL



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ELECT PWR - AC GENERATION - APU POWER NBPT - DEAD SYNCH BUS

APU PWR 1 APB

SSBSSB CLOSE

BCU 2

POWER ON ADJ

BCU 1 (E1-2)

NO BREAK POWER

NO POWER ON ADJ

AGCU

R301 APB CLOSE

LOGIC

CLOSECOMMAND

SYNCH BUSTRANSFER LOGIC

PROTECTION(P714)

SYNCH BUS

- 91 -

747 TRAINING MANUAL

General

If the synch bus has power from an external power

source and you connect power from an adjacent APU



time delay causes the XPC to open if voltage, frequency

and phase are not in limits after 6 seconds After this

ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT EXERNAL POWER



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source and you connect power from an adjacent APU

source, the no break power transfer (NBPT) logic

momentarily connects the two sources in parallel. The

adjacent XPC then opens to remove the external power

from the synch bus.

Operation

Before the NBPT logic in the BCU connects the two powersources in parallel, a comparator circuit compares



- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

If there is a frequency difference of more than 3 Hz,the BCU gives a speed command to the APU controller

(APUC). This increases or decreases the APU speed. At

the same time the APU close protection relay energizes

and a close APB signal goes to the AGCU. The AGCU

comparator monitors the voltage, frequency and phase

and closes the APB when they are in limits. The BCU

senses the position of the APB through a set of

auxiliary contacts in the APB. After the APB closes,

the BCU removes power from the XPC and it opens. Thepower on the synch bus now comes from the APU source.

and phase are not in limits after 6 seconds. After this

time delay the XPC opens and removes power from the

synch bus, and the APB closes. This causes a momentary

break in power. When the APB closes, the 6 second time

delay resets.


Sustained unlike source protection (SUSP) is aprotection circuit in the BCU. Its primary function is



starts when the APB closes. It resets when the XPC

opens. If the XPC does not open in the time limit, the

SUSP opens the XPC and the APB. This removes the two

sources from the sync bus. After a SUSP trip you must

connect the necessary power source again.

- 92 -

747 TRAINING MANUAL

CLOSE APB



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ELECT PWR - AC GENERATION - APU POWER NBPT - ADJACENT EXERNAL POWER

6

SUSP

SUSP

XPC

APB

ADJ XPC

POWER ON

SUSP TRIP

TRIP

BCU

APB

APB CLOSED

28V

AGCU

V/F/PHASE

APU PWR

APB

SPEED COMMAND

RESET

TRIP

APB/SPEED

POWER ON ADJ CLOSE

APU PWR

APU PWR

POWER ONSYNCH BUS

COMPARATOR

SYNCH BUS

CLOSED

CLOSECOMMAND

TO APUC

SYNCH BUS

TD

CONTROL

APB

CLOSEPROTECTIONRELAY

CLOSED

LOGIC

110 MS

RESET

DC

- 93 -

747 TRAINING MANUAL

General

If the synch bus has power from an IDG and you connect

power from an adjacent APU source, the no break power

the GCU. The GCU opens the GCB if the BTB is closed. If

the BTB is open, the GCB stays closed. The power on the

synch bus now comes from the APU source.

ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT IDG



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p j , p

transfer (NBPT) logic momentarily connects the two

sources in parallel. The adjacent GCB then opens to

remove the IDG power from the synch bus. If there are

two IDGs in operation, they operate the same.

Operation

Before the NBPT logic in the BCU connects the two powersources in parallel, a comparator circuit compares



- Voltage, 10 volts

- Frequency, 3 Hz

- Phase, 20 degrees

The BCU monitors APU power C phase frequency and sendsthis data as a digital reference frequency to the GCU.

The GCU increases or decreases IDG speed until the

difference between the frequency of IDG and APU power C

phase power is in limits.

The BCU energizes the APB close protection relay and

sends a close APB signal to the AGCU. The AGCU

comparator monitors the voltage, frequency and phase

and closes the APB when they are in limits. The BCUsenses the position of the APB through a set of

auxiliary contacts in the APB. After the APB closes,

the BCU sends a trip signal on the digital data bus to



time delay causes the BCU to send a trip signal to the

GCU over the digital data bus if voltage, frequency and

phase are not in limits after 6 seconds. After this

time delay the GCU opens the GCB and removes power from

the synch bus. The APB then closes. This causes a

momentary break in power. When the APB closes, the 6second time delay resets.



protective circuit in the BCU. Its primary function is



starts when the APB closes. It resets when IDG power isno longer on the adjacent synch bus. If the GCB does




- 94 -



747 TRAINING MANUAL

APB

V/F/PHASE

CLOSE APB

R301 APB

APB SSB

OPEN

APU PWR

CLOSED SSB



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ELECT PWR - AC GENERATION - APU POWER NBPT - OPPOSITE IDG

6

SUSP

CLOSE

GCB BTB

BTB

TRIP

POWER ON ADJ

APU PWR

V/F/PHASE

APU POWER

AGCU

RESET

TRIP

OPPOSITE BTB

APU PWR

SUSP RESET

BCU

APB/FREQ

GCB

TRIP

GCU

APB CLOSED

OPP APU

POWER ON

SSB CLOSED

SUSP

TRIP

SYNCH BUSCOMPARATOR

CLOSEPROTECTION(P714)

SYNCH BUS

AND GCB CLOSED

CLOSECOMMAND

C PHASE REF FREQTO GCU(S)

TD

CONTROL

APBLOGIC

110 MS

WITH NO IDGPOWER ON ADJSYNCH BUS

TRIP

PWR AVAIL

LOGIC LOGIC

- 99 -



747 TRAINING MANUAL

ELECT PWR -- AC GENERATION - APU POWER NBPT - ADJACENT AND OPPOSITE IDG

starts when the APB closes. It resets when IDG power is

no longer on the adjacent synch bus. If the GCB does


signal over the digital data bus to the GCU. The GCUopens the BTB on IDGs where the GCB did not open.



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p p

- 102 -

747 TRAINING MANUAL

SSB

V/F/PHASE

AGCU

APU PWR

POWER ON SYNCH BUS

APB

APB

COMPARATOR



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ELECT PWR - AC GENERATION - APU POWER NBPT - ADJACENT AND OPPOSITE IDG

6

RESET

APB/FREQ

TO ALL

TO ALL GCU(S)APU POWER C PHASE

OPP APU

SSBOPEN

TO ADJ GCU(S)

OPP APU

ONE OR TWO

ONE OR TWO

APU PWR

APU PWR

SUSP RESETSUSP

APB CLOSED

APB

CLOSE

BCU

CPR

TRIP

TRIP

SSB OPENED

ADJ GCBS ANDBTB CLOSED

OPP GCBS ANDBTB CLOSED

CLOSECOMMAND

PWR AVAIL

APB

CONTROL

WITH NO IDGPOWER ONADJ SYNCH BUS

110 MS

LOGIC

CLOSED

TO TRIP GCB(S)

TD

PWR AVAILFOUR GCU(S)TO TRIPGCB(S)

REF FREQ TO GCU(S) FOR BTB SUSP TRIP

- 103 -



747 TRAINING MANUAL

General

The airplane has four integrated drive generators

(IDG). Each IDG is a combined generator and constantspeed drive (CSD). The generator part gives 3 phase,

400 Hz 115 volts ac at 90 kva The CSD part keeps the

ELECT PWR -- GEN DRIVE - INTRODUCTION



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400 Hz, 115 volts ac at 90 kva. The CSD part keeps the

generator at a constant 12,000 rpm during usual

operation. This makes sure that the generator supplies

a constant 400 Hz.

The IDG power goes to the airplane through generator

feeders. The feeders have a short length of AWG 0

copper spliced to AWG 00 aluminum. The length of coppergoes in the engine compartment and connects to the

aluminum at the copper-aluminum splice in the strut.

The part of the feeders from the IDG to the bottom of

the strut has quick disconnect clamps to aid in engine

removal. The aluminum feeders go along the wing leading

edge and connect at their related generator circuit

breakers in the generator power centers.

- 106 -

747 TRAINING MANUAL



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ELECT PWR - GEN DRIVE - INTRODUCTION

INTEGRATED

GENERATOR

MEC

P615

P614P514

IDG 4

IDG 1IDG 2 DRIVE

GENERATOR

FEEDER

P515IDG 3

INTEGRATEDDRIVE

GENERATOR

- 107 -

BOEING 747-400

TRAINING MANUALATA 24

ELECTRIC PWRVersion 1

Oct 1, 2009

NOTES



FOR TRAINING PURPOSE ONLY PAGE 108 TECHNICAL TRAINING DEP



BOEING 747-400

TRAINING MANUALATA 24


Oct 1, 2009

IDG Operation and Control (cont)

The heat generated by the IDG is carried by the oil tothe air/oil heat exchanger and oil cooler then back to theIDG. The position of the air/oil heat exchanger valve is



p gnormally controlled by the GCU but can be overriddenby the electronic engine control (EEC) under someoperating conditions.

FOR TRAINING PURPOSE ONLY PAGE 109A TECHNICAL TRAINING DEP



747 TRAINING MANUAL

General

The engine power system includes:



iff i l i f ( 2)

ELECT PWR -- GEN DRIVE - ENGINE POWER COMPONENTS



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- Differential protection current transformers (12)

- Generator control current transformers (GCCT) (4)

- Generator circuit breakers (GCB) (4)

- Bus tie breakers (BTB) (4)

- Generator control units (GCU) (4)

- Integrated drive generators (IDG) (4)

- Lightning protectors (12).

- 110 -

747 TRAINING MANUAL

2

APU

FIELDOFF OFF

FIELDOFFFIELD

BREAKERSPLIT SYSTEM

21

OFFFIELD

431

GEN FIELD MAN RESET



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ELECT PWR - GEN DRIVE - ENGINE POWER COMPONENTS

GENERATOR MANUAL

IDG

ELECTRICAL SYSTEM

DIFFERENTIAL PROTECTION

GCBBTB LIGHTING PROTECTOR

OFFFIELD

OFFFIELD

OPEN

CONTROL PANEL

GENERATOR CONTROL UNITGENERATOR CONTROL

CURRENT TRANSFORMER

RESET PANEL (P461)

CURRENT TRANSFORMER(4)(12)(4)(4)(4)(4)

- 111 -

747 TRAINING MANUAL

General

Power from each IDG goes to its related load bus

through the GCB and to the synch bus through the BTB.The GCUs and the electrical system control panel

control the related BTBs and GCBs.

monitors real load and uses speed signals to keep the

correct real load balance with the other IDGs.

Excitation

The GCUs receives ac voltage from the PMG and changes

it to dc The IDG uses PMG voltage for excitation The

ELECT PWR -- GEN DRIVE - ENGINE POWER GENERATION CONTROL



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BTB Control

The electrical system control panel has a bus tie

switch for each IDG. When you set the switch to ISLN

(isolation), the BTB opens, and the ISLN light comes

on. When you set the bus tie switch to AUTO, the BTBcloses. In the AUTO position the BTB opens for a fault

trip or autoland command.

GCB/GCR Control

The electrical system control panel has a generator

control switch for each IDG. When you set the switch to

off, the generator control relay (GCR) and GCB open.

The OFF light in the generator control switch showsthat the GCB is open. When you set the control switch

to ON, the GCR closes. When the GCU senses good power

from the IDG, it closes the GCB.

Speed Control

BCU 1 sends a reference frequency to the GCUs. The GCUs

monitor the output frequency of the IDGs and compare it

to the reference frequency. A difference gives a speedcommand to the IDG. When IDGs are in parallel, the GCU

it to dc. The IDG uses PMG voltage for excitation. The

GCU controls the excitation to control the voltage and

reactive load of the generator.

Drive Disconnect

When you push the DRIVE DISC switch, the disconnectsolenoid in the IDG energizes, and the generator field

relay in the GCU opens. When you use the DRIVE DISC

switch to disconnect the IDG, you can only connect it

again on the ground at the IDG.

- 112 -

747 TRAINING MANUAL

SYNCH BUS



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ELECT PWR - GEN DRIVE - ENGINE POWER GENERATION CONTROL

IDG

GCB/GCR

GCR TRIPEXCITATION

BTB CONTROL

DRIVE DISCONNECT

GCB

BTB

GCB CONTROL

SPEED

BTB CONTROL

GCU

ELECTRICAL SYSTEM

REFERENCEBCU 1

AC BUS

OFF

BUS

ON

a

w

a

w

DRIVE

aISLN

AUTOw

DISCDRIVE

CONT

GEN

TIEBUS

CONTROL

CONTROL PANEL (P5)

FREQUENCY

PMG

- 113 -



747 TRAINING MANUAL

GCR

VOLTAGEREGULATOR



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ELECT PWR - GEN DRIVE - GENERATOR

3 PHASE

GCUCURRENT

IDG

PMG

EXCITER

MAIN

DC

3 PHASE

TRANSFORMERS

GENERATOR

GENERATOR

400HZ115/200V

1200HZ100V AC

- 115 -



747 TRAINING MANUAL



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ELECT PWR - AUTOMATIC CONTROL - GENERATOR CONTROL UNITS


- 117 -

747 TRAINING MANUAL

General

There are four GCBs and four BTBs that connect engine

power to the airplane main load buses and the synchbus. They are in the MEC in P514, P614, P515 and P615.

The breakers are a magnetic latch type and can operate

275 i 350 f 15

ELECT PWR -- MANUAL CONTROL - BTB/GCB POWER BREAKER



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at 275 amperes continuous or 350 amperes for 15

seconds. They can open up to 5000 amperes. The breakers

must get 28 volts dc to close or to open. The control

signals to the GCBs and BTBs come from the GCUs. The

GCBs and BTBs are inter-changeable with each other and

with the auxiliary power breakers.

- 118 -

747 TRAINING MANUAL

P515

P615

CLOSE28V DC



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ELECT PWR - MANUAL CONTROL - BTB/GCB POWER BREAKER

P514

P614TRIP

28V DC

COMMON

CLOSE (PERMANENT MAGNET)

- 119 -

747 TRAINING MANUAL

General

Lightning protectors give protection for the electrical

system from transients caused by lightning strikes.There are three for each generator channel. The

protectors are in P514, P614, P515 and P615.

The lightning protectors prevent equipment damage from

ELECT PWR -- AC PWR GEN AND PROTECTION - LIGHTNING PROTECTORS



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The lightning protectors prevent equipment damage from

transient voltages that are more than 252 volts. These

transient voltages go to ground through the lightning

protectors. The lightning protectors connect from the

load side of the GCBs to ground on all three phases. A

one-ampere circuit breaker is in series with eachlightning protector. This is to prevent loss of a load

bus because of a short to ground in a one related

lightning protector.

- 120 -

747 TRAINING MANUAL

P515

TOIDGLOAD



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ELECT PWR - AC PWR GEN AND PROTECTION - LIGHTNING PROTECTORS

GCBP614

P615

P514LIGHTNINGPROTECTORS

- 121 -

747 TRAINING MANUAL

Location

Six voltage harmonic distortion filter units are on the

floor beam in the right main equipment center above themain battery.

Operation

ELECT PWR -- AC PWR DISTRIBUTION - HARMONIC DISTORTION FILTER UNIT



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Voltage harmonic distortion filters minimize electrical

power degradation from the interactive video system

(IVS) and the overhead video system. The active filters

are on each phase. They sense excessive voltage

harmonics on the AC bus 3 and 4, and produce an equalharmonic 180 degrees out of phase to cancel the

harmonic.

The green light is on when there is power through the

unit. The red light stays off.

Maintenance Practices

The filter units have BIT which detects variousinternal failures. Push and hold the test switch for

five seconds. The green light goes off and the red

light comes on. A failure results in these:

- Filter shuts down

- Green light is off

- Red light is on

- ELEC FILTER FAIL status message.

- 122 -

747 TRAINING MANUAL

P180 DCE30EQUIPMENTRACK DISTRIBUTION

PANEL



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ELECT PWR - AC PWR DISTRIBUTION - HARMONIC DISTORTION FILTER UNIT

FWD

INBD

NOSE GEAR

MAINGREEN LED

RED LED

TEST SWITCH

BATTERY

WHEEL WELL(FAULT)

(NORM)

- 123 -

747 TRAINING MANUAL

General

The airplane has four generator control current

transformers (GCCT). The GCCTs give the GCUs datanecessary for control and protection. They are in the

generator power centers, P515, P615, P514 and P614.

Operation

WARNING: DO NOT DISCONNECT THE TRANSFORMER OUTPUT


POTENTIALLY HIGH VOLTAGES COULD DAMAGE THE

TRANSFORMER OR RESULT IN INJURY TO PERSONNEL.

ELECT PWR -- AUTOMATIC CONTROL - GENERATOR CONTROL CURRENT TRANSFORMERS



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The generator feeders go through the holes in the GCCT.

During system operation the coils in the GCCTs make a

current that has a relation to the current that goes

through the feeders. The GCU uses this current for:

- Over/under excitation protection

- Difference current protection

- Reverse power protection

- Real/reactive load control

- Over/under frequency protection (Real load sensing

bias).

Characteristics

Each transformer assembly has toroidal shaped cores

with secondary winding wires that connect to an output

connector. Main ac feeder lines go through the large

holes in the transformer and become the primary winding

for each transformer core. The turns ratio of all the

windings is 1000 to 1. If the primary winding (feeder

line) is 115 volts ac, secondary winding voltage is as

much as 115,000 volts with the connector off (no load).Usually secondary voltages are very low because the

secondary loads have a low resistance.

- 124 -

747 TRAINING MANUAL

P615

P515

A PHASE

B PHASE

C PHASE

DIFFERENCE

REVERSE

OVER/UNDERCURRENT EXCITATION

POWER

1 1

1



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ELECT PWR - AUTOMATIC CONTROL - GENERATOR CONTROL CURRENT TRANSFORMERS

REAL/

THESE COILS CONNECT IN

P614

P514

OF/UFBIAS REACTIVE

LOAD

1SEPARATE EQUALIZATION LOOPS

- 125 -



747 TRAINING MANUAL

C PHASE

1000

1000

P615

P515



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ELECT PWR - AUTOMATIC CONTROL - DIFFERENTIAL PROTECTION CURRENT TRANSFORMERS

A PHASE

B PHASE1000

1000

P614

P514

- 127 -

747 TRAINING MANUAL

General

To get maximum system capacity and prevent IDG overload

during parallel operation, the system must balance realand reactive loads between generators. To do this the

system compares the real and reactive loads on each

generator with the average load. The system controls

the IDG to this average value.

The example that shows uses a 10 to 1 ratio in the GCCT.

The four parallel IDGs supply a total reactive load of

210 amperes. The average current in the equalizing loop

is 21/4 or 5.25 amperes. If there are 2 amperes in thecurrent loop of IDG 1, GCU 1 senses the differential

current of 3.25 amperes. This causes more excitation to

the IDG so it gets more of the reactive load. In GCU 2

the differential current is in the reverse direction.

This causes less excitation to IDG 2

ELECT PWR -- AUTOMATIC CONTROL - EQUALIZING LOOP



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A coil in the generator control current transformer

(GCCT) senses load current from its related IDG. The

real/reactive load coils in each GCCT connect in series

to make an equalizing loop. The current in this loop isan average of the load current of all the generators in

parallel. A generator control unit (GCU) senses the

difference in the average loop current and the related

IDG current. The GCU circuits find the real and

reactive components of the load current to give speed

and electrical control of the IDG.

There are three other equalizing loops in the system:

- Over-excitation and under-excitation protection

- Over-frequency and under-frequency protection

- Difference current protection.

The loops give an out-of-balance indication to the GCU.

When an IDG is not in parallel, auxiliary contacts in

the related open BTB or GCB short the coils in the

GCCT. Auxiliary contacts of the SSB make two loops ifthe SSB is open.

This causes less excitation to IDG 2.

- 128 -

747 TRAINING MANUAL

5.255.25

REACTIVE REACTIVE REACTIVE REACTIVELOAD 20 LOAD 70 LOAD 60 LOAD 60



24-23-00

2 4 - 2 3 - 0 0 -

0 0 6

R e v

1

1 0 / 1 3 / 2 0 0 0


ELECT PWR - AUTOMATIC CONTROL - EQUALIZING LOOP

SSB

CTGENERATOR2

CT CT66

CT

GCB

BTB

AUX

GCB

BTB

AUX

GCU 3 GCU 4

5.25

KW/KVAR CUR

GCB

BTB

GCB

BTB

AUX

GCU 2GCU 1

5.25

AUX

7

5.25

ALL CONTACTORS SHOWN

IDG 2IDG 1 IDG 3 IDG 4

CONTROLCURRENTTRANSFORMER

IN CLOSED POSITION(AUX CONTACTS ARE OPEN)

SENSE MONITOR

CONTACTS3.25

CONTACTS1.75

CONTACTS.75

CONTACTS.75

AUXCONTACTS

- 129 -

747 TRAINING MANUAL

General

An electrically controlled mechanical governor controls

IDG speed. The electrical portion of the governor (trimhead) gets speed commands from the GCU trim head

control. When it is active, this trim head can keep the

output frequency of the IDG between 375 and 425 Hz.

Operation

- Master frequency: The master frequency comes from

BCU 1. It is the reference frequency when the

generator is in parallel.

- External power C phase: When you push externalpower switch 1, BCU 1 momentarily sends external

power 1 C phase frequency to the related GCUs. (GCU

1 and 2 if the SSB is open and all four if the SSB

is closed). When you push the external power 2

switch, BCU 2 sends external power 2 C phase

ELECT PWR -- GEN DRIVE - IDG SPEED CONTROL



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Operation

To find the correct speed command the GCU monitors the

frequency of the generator output and compares it to

the reference frequency in use. A difference betweenthe two frequencies causes a speed command to go to the

trim head.

To keep the real load in balance during parallel

operation, the trim head control gets A phase voltage

from the point of regulation and load current data from

the kw/kvar sense monitor. The kw/kvar current sense

monitor gets current inputs from the GCCT.

Reference Frequency

The reference frequency select circuit finds what

frequency the trim head control is to use. There are

five possible sources for the reference frequency:

- Synch bus C phase: With the GCB or BTB open and

synch bus frequency between 375-425 Hz, the GCU

uses synch bus C-phase. The exception to this iswhen the GCB opens for an underspeed or the BTB

opens for autoland.

switch, BCU 2 sends external power 2 C phase

reference frequency to BCU 1. BCU 1 sends it to the

related GCUs.

- APU power C phase: When you push the APU power 1

switch, BCU 1 momentarily sends APU power 1 C phasefrequency to the related GCUs (GCU 1 and 2 if the

SSB is open and all four if the SSB is closed).

When you push the APU power 2 switch, BCU 2 sends

APU power 2 C phase reference frequency to BCU 1.

BCU 1 sends it to the related GCUs.

- Internal reference frequency: The GCU uses an

internal reference when the reference frequency

from the BCU is more than 425 Hz or less than 375

Hz, or there is no BCU reference frequency signal.

- 130 -

747 TRAINING MANUAL

GCB

TO LOAD BUS

APU GEN 1EXT PWR 1

LIA

VA

wwON

LIA

VA

wwON



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0 0 7

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ELECT PWR - GEN DRIVE - IDG SPEED CONTROL

GCU 1/2

GOV

TRIM

REFERENCETRIM HEAD

GCCT

GCBBTB

IDG

US

GCB OPEN

BTB OPEN

AUTOLAND

APU 1

APU GEN 2EXT PWR 2

LIAVA

ww

ON

BCU 2

MASTER

BCU 1SYNCH

EXTERNAL

SYNCH APU 2 C

EXTERNAL PWR

GCU

REFERENCE

INTERNAL

SYNCH BUS

HEAD

CONTROL

LOAD

FREQUENCY

SELECT

FREQUENCY

420-380 HZ

ENABLE

PHASE

3/4

FREQUENCY

POWER 1C PHASE

C PHASE

FREQUENCY

2 C PHASE

PHASE

LIAVA

ww

ON

CURRENT KW/KVARCUR SENSEMONITOR

REFERENCE BUS

BUS C

- 131 -

747 TRAINING MANUAL


ELECT PWR -- GEN DRIVE - GCR AND VOLTAGE CONTROL



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- 132 -

747 TRAINING MANUAL


General

The PMG supplies three phase, 100v ac and sends it to

the GCU for:

- Voltage regulation

- Internal power supplies

- Frequency indication (metering)

Frequency sensing (over/under frequency

the power to the exciter generator field to keep 115v

ac. During parallel operation the kw/kvar current sense

monitor gets inputs from the GCCT.

The voltage regulator gets inputs from the monitor. The

monitor uses the output of the GCCT to find the

reactive load of the generator. The voltage regulator

uses this data to increase or decrease the excitation

current to keep the correct reactive load of the



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- Frequency sensing (over/under frequency

protection)

- Field current (excitation).

Power to the GCU comes from three possible sources.

This makes sure that the bus protection circuits in the

GCU have power when the bus has power. These are the

possible sources:

- PMG voltage

- Main hot battery bus (battery switch on)

- DC ground handling bus.

Voltage Regulation

PMG voltage goes to the GCR. When the GCR closes, PMG

voltage goes to the voltage regulator. The voltage

regulator controls the PMG voltage and makes it a

pulsed dc current.

The dc current (excitation) goes to the exciter

generator field. This gives excitation power to the

main generator field. This excitation power causes the

main generator to supply 3 phase, 400 Hz, 115v ac. The

voltage regulator monitors this voltage and controls

current to keep the correct reactive load of the

generator.

GCR Control

The GCR is in the GCU and is a latch type relay with a

trip and a close coil. This relay opens or closes to

remove or connect the generator output to the voltage

regulator. These manually control the GCR:

- Generator control switch

- Field reset switch

- Fire switch

- Drive disconnect switch.

The control function of the generator field reset

switch on the P461 panel is active only when the

generator control switch is off.

The GCR automatically opens for one of these faults:

- SPMG (short on PMG)

- Overvoltage

- Undervoltage

- Differential fault

- 133 -

747 TRAINING MANUAL


- Overfrequency

- Underfrequency

- Generator diode failure

- Open phase

- GCU internal failure.

After a fault trip occurs, you must set the GCB switch

to the off position then back to the on position to

make the field operate again.



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If there is still an overfrequency or underfrequency

after a reset, the GCR and GCB does a trip again. If

this occurs, disconnect the IDG. The software causesthe drive light to come on and makes the EICAS message

ELECT DRIVE show after the second trip.

- 134 -

747 TRAINING MANUAL

LOAD

GCCT

VOLTAGEEXCITER

MAIN GEN

BUS

1

OFF

ON

a

w

GEN REGULATOR

CURRENTCONT

GCBBTB

KW/KVARCUR SENSEMONITOR

GEN

CLOSE

OPEN



24-11-00

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0 0 6

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ELECT PWR - GEN DRIVE - GCR AND VOLTAGE CONTROL

TRUPOWER

OF/UF

FREQUENCY

GCU

TO BCU FOR

PMG

IDG

ELECTRICAL SYSTEM

DRIVE

GENERATOR MANUAL

MAIN HOT

FIRE

S

TRIP

RFAULT

DRIVE

GCR

CLOSE

TRIP

wOFFFIELD

CYCLE

TRIP/

CLOSE

TRIP

BCU STBYBAT SW

DC

GEN

BAT BUS

PWR XFR

FREQUENCYINDICATION

PROTECTION

SENSE

SUPPLY

REGULATOR

GCS ORFIELD SWTO RESET

LOGIC

TRIPS

RESET PNL (P461)

CONTROL PNL (P5)

DISC

GCB

GHB

a

w

CLOSE

OS

OS

SW

RLY (P414)

2ND TRIP COUNTER

TO EICAS

- 135 -

747 TRAINING MANUAL


ELECT PWR -- GEN DRIVE - GCB CONTROL



24-11-00 2 4 - 1 1 - 0 0 - 0 0

8

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- 136 -

747 TRAINING MANUAL


General

The generator control switch (P5) and the GCU control

the GCB. When you put the generator control switch tothe OFF position, the GCB automatically opens. When you

put the switch to the ON position, the GCU closes the

GCB if related system conditions are true.

GCB Close

reset the SUSP circuit (two unlike sources in parallel

for more than 110 ms). With the GCB and BTB closed a

digital signal goes to the BCU to open the XPC or APB

that gives power to the adjacent synch bus.

GCB Trip

The GCB opens for:



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These system conditions must all be true for the GCU to

close the GCB:

- Generator control switch to on

- GCR closed (no faults)

- No underspeed

- Dead load bus or generator voltage, frequency and

phase match the power on the synch bus (auto

parallel)

- No APB or XPC closed inputs with BTB closed

- No inputs from last source on logic

- Good power: voltage between 104.5 and 131 volts

sensed at the point of regulation (generator side

of GCB) and frequency between 375 and 425 Hz (input

from the PMG).

When these conditions are true, a close signal goes to

the GCB through a one shot that gives power to the GCB

for 300 ms. This close signal goes to the GCB through

the usually closed contacts of the GCB protection

relay. After the GCB closes, a set of auxiliary

contacts in the GCB causes the generator off light (P5)

to go off. Another set of contacts cause the BCU to

- Generator control switch to off

- Any malfunction that causes the GCR to open

- Underspeed

- An XPC or APB closed signal with the BTB closed(APU or external power no break power transfer

logic trip of a GCB)

- Last source on logic trip; last source logic trip

comes from the BCU for power transfers that use the

BTB. Last source on is the power source connected

to the airplane.

These are examples of last source on power:

- Example 1; The BTB is open and the IDG gives power

to its related load bus. If you put APU power on

the synch bus, the APU is the last source on. If

you then close the BTB, the GCB opens.

- Example 2; The BTB is open and external power gives

power to the synch bus. If you close the generator

control switch, and the IDG gives power to its

related load bus, the IDG is the last source on. If

you then close the BTB, external power

disconnects.

- 137 -

747 TRAINING MANUAL


Signals that open the GCB also energize the GCB

protection relay. This opens the close circuit from the

GCU.

Break Power Transfer

A break power transfer occurs when the XPC or APB opens

before the GCB closes. This causes an interruption of

power on the synch bus. The break power transfer lets

the IDG give power to the synch bus when it cannot auto



24-11-00 2 4 - 1 1 - 0 0 - 0 0

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the IDG give power to the synch bus when it cannot auto

parallel with external or APU power. The break power

transfer occurs when APU or external power give power

to the synch bus and:

- Generator control switch is on

- GCR closed (no faults)

- No underspeed

- BTB is closed

- there is a 6 seconds time delay.

If the synch bus has power by one IDG, and you try to

connect another IDG that cannot match the synch busfrequency, the GCB does not close.

- 138 -

747 TRAINING MANUAL

ON w

OFFa

DRIVE

w

a

P5

ARINCRCVR

TD 6

TO BCUFOR XPCAND APBTRIPS(ADJ SYNCHBUS PWR)

A

DTUNDERSPEED

GCR CLOSED

BTB CLOSEDGCS ON



24-11-00

2 4 - 1 1 - 0 0 - 0 0 8

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1 0 / 2 5 / 1 9 9 9


ELECT PWR - GEN DRIVE - GCB CONTROL

FROM

TO

GCU GCB PROTECTION

CLOSE

OPEN

AUX

GCB

SO

GCS CYCLED

CONTACTS

O

AUTO PARALLEL

GCB CLOSED

CONT

LT &BCU

SUSP

GOOD PWR

ARINCRCVRBCU

A

LAST SOURCE ON LOGIC TRIP

GCB TRIP AND RESET LOGIC

APBOR XPCCLOSED

S

R

UNDERSPEED

DEAD LOAD BUS

SW

GEN

FOR

OFF

- 139 -



747 TRAINING MANUAL

ELECT PWR -- GEN DRIVE - BTB CONTROL

General

The BTB manually operates with the bus tie switch. If

you put the switch to the isolation (out) position, theBTB opens and the ISLN light comes on. If you put the

switch to the AUTO (in) position, the BTB closes

through auto parallel, dead synch bus or GCB logic.

With the BTB closed the ISLN light goes out.

BTB Close

- Load bus malfunction (differential malfunction)

- Synch bus malfunction

- SUSP with the GCB closed

- Over or under excitation; A parallel conditionmalfunction that opens the BTB first. If the

condition continues, the system thinks it is a

voltage fault and the GCR and GCB open

- Difference current; Generator output is different

than the average of the other generators that

operate in parallel by 35 to 40 amperes



24-11-00 2 4 - 1 1 - 0 0 - 0 0 9 R

e v

1

1 0 / 2 2 / 1 9 9 9


BTB Close

The BTB closes if all of these conditions are true:

- No load bus malfunction (differential malfunction)

- No synch bus malfunctions (differential or

negative sequence)

- No SUSP fault with the GCB closed

- No generator power faults (over or under

excitation, reverse power, difference current,

open phase, over or under frequency)

- No autoland request

- Bus tie switch in AUTO- No adjacent synch bus power, auto parallel

conditions true or GCB open. If the generator

cannot match the synch bus power, the BTB does not

close.

Close signals to the BTB go through the usually closed

contacts of the BTB protection relay.

BTB Trip

The BTB opens for:

operate in parallel by 35 to 40 amperes

- Reverse power; This does not let the electrical

system operate the IDG as a motor (8+/-1 kw)

- Open phase; This is when the lowest phasegenerator feeder current is less than 6+/-5

amperes and the next lowest is 55+/-5 amperes or

more

- Over and under frequency; below 370 Hz and above

430 Hz

- Autoland request; When the autoland signal goes

away, the BTB closes again

- Bus tie switch to ISLN; With the BTB switch in the

ISLN position a signal goes directly to open theBTB and reset internal fault latches in the GCU.

Signals that open the BTB also energize the BTB

protection relay. This opens the close circuit from the

GCU.

Auto Reclose

Auto reclose of the BTB occurs when the BTB opensautomatically in any channel, and subsequently the GCB

opens automatically in the same channel. The BTB does

- 141 -

747 TRAINING MANUAL

ELECT PWR -- GEN DRIVE - BTB CONTROL

not close again by the auto reclose logic if the BTB

opened because of load bus malfunctions, synch bus

malfunctions, SUSP, autoland or by manual operation of

the bus tie switch. You must put the bus tie switch to

the ISLN position then to the AUTO position to get the

BTB to close.



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- 142 -

747 TRAINING MANUAL

LOAD

SUSP

RESET

GENERATOR

ISLNa

SYNCH

FROM ARINCBCU RCVR

POWERFAULTS

S

R

GCB

BUS FAULT

BUS FAULT

CLOSED



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- 0 0 9

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ELECT PWR - GEN DRIVE - BTB CONTROL

TO BCU FOR

AUTO PARALLEL

DEAD ADJ SYNC BUS

BTB OPEN

LIGHT

AUTO

AUTO LAND

GCU

CYCLE

ISLNa

AUTOw

BUS TIE

GCB OPEN

BTB

CLOSE

OPEN

AUX

BTB

SO

S

GCS ON

BTB

AUTO RECLOSE

GCB

POSITIONLOGICCONTACT

PROTECTION

SWITCH

TO RESET

R

SO

OPENS

OPEN

- 143 -

BOEING 747-400TRAINING MANUAL

ATA 24


Oct 1, 2009

POWER TRANSFER SUMMARY

This chart summarizes all power transfers to sources on

the left side. The chart shows contactors or breakerstripped during normal no break power transfers andnon-normal break power transfers.





ATA 24


Oct 1, 2009



FOR TRAINING PURPOSE ONLY PAGE 143B TECHNICAL TRAINING DEP


ATA 24


Oct 1, 2009

NOTES





ATA 24


Oct 1, 2009

ENGINE POWER SYSTEM (IDG)

General

The IDG portion of the engine power system involvesthe mechanical aspects of the IDG and its oil coolingcomponents.

Operation

Control

Control and monitoring of the IDG is done by the GCU.The GCU receives oil temperature, oil pressure, andIDG speed signals. It sends speed commands to theIDG governor and control signals to the air/oil heatexchanger valve



Operation

The CSD portion of the IDG is a hydromechanicaldevice. It adds or subtracts speed from the variableinput of the engine gearbox to maintain the IDGgenerator at 12,000 rpm.

IDG oil is used for speed control, lubrication and cooling.

Heat generated by the IDG is cooled by passing the oilthrough an air/oil heat exchanger and a fuel cooled oilcooler. The cooled oil is then returned to the IDG. Theoil cooler is the primary means of cooling the oil but isassisted by the air/oil heat exchanger under certainoperating conditions.

exchanger valve.

Oil temperature comes from two temperature bulbsinside the IDG and is used for:- High oil temperature light- Oil out temperature indication- oil rise temperature indication- Air/oil heat exchanger valve control

oil pressure comes from an oil pressure switch insidethe IDG and is used for the IDG DRIVE light.

Speed inputs come from the magnetic pickup unit (MPU)and are used for underspeed trips and airmode inhibits.

Speed commands from the GCU to the IDG are used tocontrol IDG speed to maintain reference frequency andreal load division.



ATA 24


Oct 1, 2009

Control (cont)

Air/oil heat exchanger valve control signals are sent to

the valve to control the opening and closing of the valve.The signal must pass through an override pressureswitch. The pressure switch along with the air/oil heatexchanger valve override solenoid allow the EEC tooverride the GCU signal and control the valve.



FOR TRAINING PURPOSE ONLY PAGE 144B TECHNICAL TRAINING Dep


ATA 24


Oct 1, 2009




747 TRAINING MANUAL

General

The IDG system includes these components:

- Air/oil heat exchanger valve override solenoid -controls the position of the override pressure

switch. It is controlled by the EEC and is at the

1:00 position under the intermediate fan case

- Override pressure switch - when closed it lets the

GCU control the air/oil heat exchanger valve. When

open, it causes the air/oil heat exchanger valve

t It i t th 1 00 iti d th

ELECT PWR -- GEN DRIVE - IDG COMPONENTS



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to open. It is at the 1:00 position under the

intermediate fan case

- Oil cooler and bypass valve - cools IDG oil withfuel. They are at the 9:00 position below the 2.9

bleed valve.

- IDG - Maintains the IDG generator speed at 12000

rpm. It is on the aft, left side of the main

gearbox.

- Air/oil heat exchanger and valve - cools IDG oil.

They are at the 3:00 position under the

intermediate fan case.

- 146 -

747 TRAINING MANUAL

OVERRIDE

IDG AIR/OIL HEAT EXCHANGER

VALVE OVERRIDE SOLENOID

HPC SECONDARY FLOW CONTROL

VALVE AND IDG AIR/OIL

HEAT EXCHANGER VALVE

PRESSURE

SWITCH



24-11-00

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ELECT PWR - GEN DRIVE - IDG COMPONENTS

OIL COOLER AND BYPASS VALVEIDG AIR/OIL HEAT

EXCHANGER AND VALVEIDG

HEAT EXCHANGER VALVE

OVERRIDE SOLENOID ASSEMBLY

- 147 -

747 TRAINING MANUAL

Right Side

These are on the right side of the IDG:

- IDG housing - a two part magnesium casting with adry weight of 118 pounds

- Oil ports - the oil in and oil out ports give a

connection point between the IDG and the external

oil cooling system; a pressure relief valve at the

oil in port gives protection to the IDG housing

from overpressure if there is a core rupture of the

fuel/oil cooler

60 psid; the differential pressure indicator does

not operate below 145 F to prevent a nuisance

indication

- Electrical connectors - two connectors (A and B)

make an interface with airplane wiring forcontrol, protection, and monitor circuits.

Left Side

These are on the left side of the IDG:

- Terminal block - the main generator stator three

ELECT PWR -- GEN DRIVE - IDG GENERATOR



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fuel/oil cooler

- Governor adjustment - a mechanical adjustment that

sets the basic speed of the IDG- Drain and fill ports - you remove the case drain

plug to drain the oil from the IDG case; the

service couplings connect to the pressure fill

port and overflow drain port to do servicing of the

IDG; the overflow drain connects to an internal

standpipe

- Case thermal relief valve - lets hot IDG oil drain

overboard if the IDG oil temperature is more than

430F (221C)- Oil level indicator - a prismatic sight glass that

gives a visual indication of low IDG oil

- Scavenge filter and delta pressure indicator - a

non-bypass filter on the discharge side of the

scavenge pump removes contamination from the oil

that goes out of the IDG; the scavenge filter

contains a pop-out delta pressure indicator; the

red button comes out when the pressure drop gets to

Terminal block the main generator stator three

phase output and neutral output leads connect at a

four stud terminal block- Disconnect reset ring - lets you do a reset of a

disconnected IDG on the ground; this engages the

IDG input and interconnect shafts

- Muff spline - a 1.5-inch, male spline on the input

drive shaft that you can remove; it connects the

IDG shaft to the engine gearbox; the input shaft

shear section breaks if there is an input torque of

9000 +/-400 inch-pounds.

- 148 -

747 TRAINING MANUAL

SCAVENGE FILTER CASE THERMALRELIEF VALVEDELTA P INDICATOR

(ACTIVATED)

ADJUSTMENTGOVERNOR

FILL PORTPRESSURE

OIL IN

OIL OUT

DRAIN PORTOVERFLOW

CONNECTOR BELECTRICAL



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ELECT PWR - GEN DRIVE - IDG GENERATOR

CONNECTOR A

RIGHT SIDE

LEFT SIDE

FILTER

INDICATORLOW OIL LEVEL

CASE

SERVICE

RESET RINGDISCONNECT

SHEAR SECTIONDRIVE SHAFT

SPLINEMUFF

COVERTERMINAL

GENERATOR

ELECTRICAL

OIL OUT

SCAVENGE COUPLINGS

DRAIN

- 149 -

747 TRAINING MANUAL


ELECT PWR -- GEN DRIVE - IDG OPERATION



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- 150 -



747 TRAINING MANUAL

ELECT PWR -- GEN DRIVE - IDG OPERATION

clutch to disconnect and stop the operation of the IDG.

You cannot reset the thermal disconnect. You can reset

the electrical solenoid disconnect.

Case Thermal Relief

If the IDG temperature goes above 450F (232C), a solder

pellet melts and lets all of the oil drain from the

IDG.



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- 152 -

747 TRAINING MANUAL

VARIABLE

OIL-IN

LEFT PUMP

RIGHT PUMP TO

GOVERNORMAG

CHARGE

CONT CYL

FIXED

DEAERATOR

EXTERNAL

FROM

TO SUMP

CHARGE

DISPLACEMENTHYDRAULICUNITS AND MOTOR

AND MOTOR SUMP

TRIM

DISPLACEMENTHYDRAULICUNITS

PUMP

TEMP BULB

CIRCUITBYPASSVALVE

COOLER



24-11-00

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0 - 0 1 3

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ELECT PWR - GEN DRIVE - IDG OPERATION

OUTPUT

PLANETARY

GENERATOR

CHARGE PUMP

CONTROL

WORKING

CHARGE

RETURN OILSUMP OIL

CHARGE

TO

TO EXT

DISCONNECT

INPUT

DISCONNECTINVER SCAV

SCAV SCAV

OIL-OUT

CHARGE

INPUT

PRESSURE DIFFERENTIAL

CASE THERMAL

PRESSURESWITCH

PRESSURE

PRESSURE

PRESSURE

SUPPLY OILRELIEF VALVE

GEAR

DIFF

SPEED SENSOR

SOLENOIDPUMP

PUMP FILTER

INDICATOR

RELIEFVALVE

SHAFT

RESET RING

CIRCUITBYPASSVALVE

COOLER

TEMP BULB

- 153 -

747 TRAINING MANUAL

General

You can disconnect the IDG input shaft from the

interconnect shaft from the flight compartment. This

lets the engine continue to operate while a defectiveIDG stops.

Operation

Push the guarded drive disconnect switch on the P5

panel to disconnect the IDG. A disconnect solenoid

energizes and lets a spring-loaded plunger engage the

interconnect shaft This ca ses the interconnect shaft

the solenoid nose pin moves into position, and you hear

a click.

Thermal Disconnect

The IDG also has a thermal disconnect in the disconnect

solenoid. The thermal material uses solder in a closed

chamber. At temperatures more than 213C (415F), the

solder melts and lets a spring retract the solenoid

pin. This lets the plunger engage the interconnect

shaft to disconnect the IDG.

Yo can not reset a thermal disconnect

ELECT PWR -- GEN DRIVE - IDG DISCONNECT - FUNCTIONAL DESCRIPTION



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interconnect shaft. This causes the interconnect shaft

to move away from the input shaft. This disconnects theIDG from the input shaft.

The same disconnect signal goes to the GCU to open the

GCR and GCB. This isolates the generator from its

electrical load. When the IDG disconnects, a DRIVE DISC

advisory and status message show on EICAS.

Maintenance Practices

Do not push the disconnect switch unless the engine is

at or above idle speed. You can push the disconnect

switch with the engine off. You must then reset the IDG

before you start the engine. The dog teeth do not fully

disconnect if the engine is less than idle speed or

off.

You can only reset the IDG on the ground with the

engine off. To do this, pull out the reset ring until

You can not reset a thermal disconnect.

- 154 -

747 TRAINING MANUAL

DISCONNECT

DRIVE

DISCONNECT

PLUNGER

RAMP

GEN DR DISC

THERMAL

P180CLUTCH

SOLENOID

DISCONNECTSOLDER

RESET RING

28V DCBAT BUS



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ELECT PWR - GEN DRIVE - IDG DISCONNECT - FUNCTIONAL DESCRIPTION

TRIP

GCU BCU(S) EIU(S)

GCR

GCB

GEN

DRIVE

INTERCONNECT

DRIVE DISC 1

AUX EICAS

>DRIVE DISC 1

MAIN EICAS

BUS

DRIVE

w

a

w

a

ON

OFF

DISC

CONT

DISCSWITCH

TRIP

STATUS PAGE

ADVISORY

INPUTSHAFT

- 155 -

747 TRAINING MANUAL

General

A speed sensor on the interconnect shaft senses the IDG

speed. The speed sensor is a magnetic pickup unit

(MPU). As each tooth on the shaft comes near to thesensor, it causes a current in the sensor. This signal

goes to the speed detector circuit in the GCU. At less

than 4525 rpm a trip signal goes to the GCB for an

underspeed condition. The sensor also sends signals to

inhibit undervoltage or underfrequency trips until the

IDG input speed is more than 4525 rpm. At 6100 rpm and

above the GCU sends a digital signal to the bus control

units The BCUs use this signal to cause airmode

ELECT PWR -- GEN DRIVE - IDG SPEED SENSING



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units. The BCUs use this signal to cause airmode

inhibits.

These are the related engine values for IDG input

speeds of 4525 and 6100 rpm:

- PW 54.3 and 73.3% N2

- GE 55.3 and 74.6% N2

- RR 50.0 and 67.4% N3.

- 156 -

747 TRAINING MANUAL

INPUT

MPUINPUT

IDG

SHAFT

SPEEDSENSOR



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ELECT PWR - GEN DRIVE - IDG SPEED SENSING

AIR

BCU 1

BCU 2

<4525

>6100

SPEED DETECTOR

US LOGIC

ARINC

US TRIPGCB

GCU

UNDER SPEED

RPM

RPM429 XMTR

CIRCUITS MODE

AIRMODE

INHIBITS

- 157 -

747 TRAINING MANUAL

General

There is a mechanical governor in the IDG that controls

its speed. The governor is a spring-biased flyweight

operated hydraulic control valve. During usualoperations there is a relation between the position of

the flyweights and a magnetic field supplied by a coil

above the flyweights. The GCU controls the current in

the coil. This sets the position of the flyweights and

thus the speed of the IDG. This lets the GCU adjust the

speed of the IDG to keep the reference frequency and kw

load balance.

ELECT PWR -- GEN DRIVE - IDG SPEED CONTROL



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- 158 -

747 TRAINING MANUAL

KW CURRENT

TRIM

IDG VOLTAGE

GENERATOR CONTROL UNIT

REFERENCE

CONNECTOR A

MAGTRIMCOIL

HEADCONTROL

FREQUENCY



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ELECT PWR - GEN DRIVE - IDG SPEED CONTROL

IDGGOVERNOR

FLYWEIGHTS

DRAIN TO

CHARGE OILCONTROLCYLINDER

(SUPPLY)

CASE

- 159 -

747 TRAINING MANUAL

General

The GCU monitors oil temperature to and from the IDG

cooling loop. It gets these temperatures from two

resistive type temperature bulbs. The oil outtemperature bulb senses the temperature of the oil that

goes out of the IDG to the cooling loop. The oil in

temperature bulb senses the temperature of the oil that

comes in from the cooling loop. The oil in and oil out

temperatures go to the oil temperature processor

circuit in the GCU. The temperature processor supplies

signals to the BCU for:

DRIVE X TEMP SNS status message shows if oil out or oil

in temperature is more than 260C or less than -70C.

Maintenance Page

Oil out and Oil rise temp shows on the maintenance page

at all times. EICAS makes a snapshot if IDG rise

temperature is more than 10C above than the other

generators.

CMC Messages

To find low IDG oil quantity, the GCU software monitors

ELECT PWR -- GEN DRIVE - IDG OIL TEMPERATURE



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- Main EICAS (advisory message)- Auxiliary EICAS (status message)

- Maintenance page (indication).

Main EICAS

If oil pressure is less than 140 psi, or oil out

temperature is more than 185 C, EICAS shows an ELEC

DRIVE 1-4 advisory message and makes an auto snapshot.

For this to occur the engine must be on, and the IDGconnected.

Auxiliary EICAS

IF the IDG outlet temperature is more than 155C but

less than 260C for 10 minutes, or oil pressure is less

than 140 psi, EICAS shows an ELEC DRIVE 1-4 status

message and makes an auto snapshot. For this to occur,

the engine must be on, and the IDG connected.

the cycle rate of the charge pressure switch and makesa CMC message IDG-X LOW OIL QUANTITY.

- 160 -



747 TRAINING MANUAL

General

The IDG air/oil heat exchanger gives more cooling as

necessary for the IDG oil. This occurs when engine

power is low or IDG oil temperature is high. The heatexchanger valve controls air to the heat exchanger.

Heat Exchanger

The air/oil heat exchanger is a tube and fin assembly

in one housing. The oil in and return ports are on the

aft face of the heat exchanger.

position. Switches on the bottom edge of the valve body

provide valve position signals to the GCU. A visual

valve position indicator is on the top edge of the

valve body.

ELECT PWR -- GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER AND VALVE



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Valve

The air/oil heat exchanger valve is a two-position

valve that ducts fan air or 2.5 bleed air to the heat

exchanger. Which air is used for cooling depends on the

position of the 2.5 bleed ring of the engine. When the

2.5 bleed ring is open (low engine power), 2.5 air is

used for IDG oil cooling. At high engine power the 2.5

bleed ring is closed and fan air is used for cooling.

The heat exchanger valve is on the forward face of theheat exchanger. It consists of these three main

subassemblies:

- Solenoid

- Dual butterfly valves mounted on a single shaft

- Fuel pressure driven actuator.

The valve is solenoid controlled and hydraulically

operated. It is either fully open or fully closed. Thevalve is spring loaded to the open (fail safe)

- 162 -

747 TRAINING MANUAL

CASE

INTERMEDIATE

2.5ORAIRFAN

VALVEEXCHANGERIDG AIR/OIL



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ELECT PWR - GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER AND VALVE

OIL-INPORT

AIRBLEED

VALVESBUTTERFLY

CONNECTORELECTRICAL

HEAT EXCHANGERIDG AIR/OIL

PORTOIL-OUT

FWD

- 163 -



747 TRAINING MANUAL

FUEL OUT

COOLING COREENGINE OIL

CORECOOLINGIDG OIL



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ELECT PWR - GEN DRIVE - IDG OIL COOLER

PUMP FILTER)(TO FUELFUEL OUT

OIL INIDG

OUTIDG OIL

BOOST STAGE)(FUEL PUMPFUEL SUPPLY

BYPASS VALVEFUEL PUMPFUEL FROM

- 165 -

747 TRAINING MANUAL

General

When the engine oil temperature is less than 160C or N2

speed is more than 72%, the EEC energizes the IDG

air/oil heat exchanger valve override solenoid to letPs3 air pressure close the override pressure switch.

This connects the GCU to the IDG air/oil heat exchanger

valve so that the GCU can control it.

When IDG oil temperature is less than 127C, the GCU

supplies 28v dc through the pressure switch to the heat

exchanger valve control solenoid. When the control

solenoid is energized, fuel pressure (PF) closes the

heat exchanger valve

ELECT PWR -- GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL



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heat exchanger valve.

If the IDG oil temperature is more than 127C, the GCU

removes power from the control solenoid of the heat

exchanger valve. When power is removed, the solenoid

de-energizes and removes fuel pressure to let the

spring open the valve. On decreasing IDG oil

temperature, the GCU closes the valve at 104C.

There is a switch in the heat exchanger valve thatsenses valve position for the GCU. This lets the GCU

determine proper operation of the valve.

- 166 -

747 TRAINING MANUAL

EEC

GCU

SUPPLYPOWER

>127CPROCESSORTEMP

SWITCHPRESSOVERRIDE

PS3

TO GCUPOSITIONVALVE

CLOSED

OVERRIDE SOLENOID

EXCHANGER VALVEIDG AIR/OIL HEAT



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ELECT PWR - GEN DRIVE - IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL

IDG

PFOUTFUEL

INFUEL

COOLEROILFUEL

OIL OUT

AIRBLEED2.5ORAIR

TEMPERATURE

EXCHANGER VALVEIDG AIR/OIL HEAT

FAN

INLET OIL

SENSOR

- 167 -

747 TRAINING MANUAL

General

The GCU provides 28v dc to close the IDG air/oil heat

exchanger valve and removes the voltage to open the

valve. The GCU monitors these valve command signals aswell as valve position. From these, the GCU can

determine if the valve fails.

EIU Logic

If the GCU senses a difference between the commanded

position and the actual valve position, a disagreement

condition exists. If the disagreement exists for longer

than 6 seconds the GCU sends a valve failed signal to

ELECT PWR -- GEN DRIVE - IDG COOLING VALVE FAILURE



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than 6 seconds, the GCU sends a valve failed signal tothe BCUs. When it receives the valve failed signal, BCU

1 (BCU 2 if BCU 1 has failed) sends a valve failed

signal to the EIUs. If engine N2 speed is 88% or more

and the valve is not being commanded open by the EEC

then after 60 seconds, the EIUs cause ELEC IDG VALVE to

show on the EICAS status page.

- 168 -

747 TRAINING MANUAL

6 SECTD

TEMPERATUREPROCESSOR

VALVEPOSITIONCONTROLLOGIC

IDG 1

DISAGREEMENT

TRANSMITTER429

BCU 1 BCU 2

- N2 >88%

IDGTEMPERATURE

VALVECOMMANDS



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ELECT PWR - GEN DRIVE - IDG COOLING VALVE FAILURE

GCU 1

2, 3, AND 4 ARE SIMILARNOTE: SYSTEM 1 SHOWN,

EIU

ELEC IDG 1 VALVE

EICAS STATUS PAGE

OPEN BY EEC

N2 >88%- NOT COMMANDED

- (60 SEC TD)

AOC VLV 1

VALVE POSITION

- 169 -

747 TRAINING MANUAL

General

The IDG air/oil heat exchanger valve override solenoid

is one of two solenoids mounted to a common valve

housing. the solenoid controls filtered Ps3 air to theoverride pressure switch. This solenoid is controlled

by the electronic engine control (EEC) and is used to

override GCU commands. The EEC de-energizes the

override solenoid when it senses engine oil temperature

above 160`C or engine speed below 72% N2. De-energizing

the solenoid vents Ps3 air from the pressure switch

causing it to open. This removes power from the IDG

air/oil heat exchanger valve control solenoid causing

the valve to go open. The override solenoid is not linereplaceable

ELECT PWR -- GEN DRIVE - OVERRIDE SOLENOID AND PRESSURE SWITCH



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the valve to go open. The override solenoid is not linereplaceable.

Pressure Switch

The IDG air/oil heat exchanger valve override pressure

switch is a single pole, double throw type switch. It

is spring loaded open when no air pressure is applied

to it. The switch is a line replaceable unit.

- 170 -

747 TRAINING MANUAL

INTERMEDIATE

PS3 MUSCLE

PS3

LEFT SOLENOID

NORMAL MODE (ENERGIZED)

IDG AIR/OIL HEATPRESSURETO PRESSURESWITCH

CASE

EXCHANGER VALVEOVERRIDE SOLENOID



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ELECT PWR - GEN DRIVE - OVERRIDE SOLENOID AND PRESSURE SWITCH

FWD

IDG AIR/OIL HEAT

VENT

PRESSURE

PS3

LEFT SOLENOID

SWITCH VENTPRESSURE

OVERRIDE MODE (DEENERGIZED)

EXCHANGER VALVEOVERRIDE PRESSURESWITCH

- 171 -

747 TRAINING MANUAL

General

You service the IDG with a pressure fill type system.

Pressure and drain lines attach to the related

couplings on the IDG. When you attach the pressure fillline to the IDG, a check valve in the elbow coupling

opens to let the IDG fill by pressure. When you fill

the IDG through the pressure fill coupling, oil flows

first through the IDG scavenge filter then through the

external oil circuit and back to the IDG. Air in the

circuit goes out in front of the oil to the overflow

drain. The oil level goes up until it gets to the top of

the overflow drain. This is the correct fill level for

the IDG oil system. The IDG oil level is correct whenoil goes out of the overflow drain and the flow

ELECT PWR -- GEN DRIVE - IDG SERVICING



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oil goes out of the overflow drain and the flow

decreases to a drip after you turn off the fill

pressure. You must let a minimum of one quart of oil go

out of the IDG overflow drain to make sure that you

serviced the IDG correctly.

WARNING: MANY WARNINGS AND CAUTIONS ARE CONTAINED IN

THE MAINTENANCE MANUAL REGARDING IDG

SERVICING. FAILURE TO ADHERE TO THEMAINTENANCE MANUAL PROCEDURES MAY RESULT IN

IMPROPER IDG SERVICING AND SUBSEQUENT IDG

FAILURE OR INJURY TO PERSONNEL.

- 172 -

747 TRAINING MANUAL

TO SUMPSCAVENGE

AIR/OIL

FUEL/OIL

AIR EXHAUST

250 PSI

CHARGE

DE-AERATORCHARGEPRESSURE

RELIEFVALVE

COOLER

HEAT

EXCHANGER

PUMP

OIL IN

OIL OUT



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ELECT PWR - GEN DRIVE - IDG SERVICING

OVERFLOW

SCAVENGE

350 PSI

SUMP

PRESSURE

STAND

IDG

PRESSURE

OIL LEVEL

CONTAINER

OVERFLOW

IDG

FILTER

SCAVENGEPRESSURE

RELIEFVALVE

OIL LEVEL

SIGHT GAUGE PIPE DRAIN COUPLING

DRAIN

FILLCOUPLING

FILL

COUPLING

INDICATOR

FWD

COUPLING

SCAVENGEPUMPS

CASETHERMALRELIEFVALVE

- 173 -

747 TRAINING MANUAL

General

The IDG oil level indicator is on the lower right side

of the IDG. You use it to do a visual check of the IDG

oil level. The graphic shows the indicator with the IDGoil at three different levels.

The left view shows a very low oil level. The indicator

shows a large bright spot.

The middle view shows an oil level approximately one

quart low. The indicator shows a light area in the

center.

The right view shows a full IDG. The indicator shows a

ELECT PWR -- GEN DRIVE - IDG OIL LEVEL INDICATOR



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g

fully dark area with an OK.

You must service an IDG that shows the left and middle

indications.

- 174 -



747 TRAINING MANUAL

General

The scavenge filter does not have a bypass. It removes

contamination from the oil that goes out of the IDG. It

has a filter element and a differential indicator on

the aft face of the IDG.

The differential pressure indicator does not operate

below 145 F. This prevents a nuisance indication.

If the indicator is out, you must replace the IDG. If

the filter shows damage or there is indications that

contaminated oil went through it, you must flush the

external oil circuit before you can operate a new IDG.If there is no filter damage and no indication the

i d il h h i d h

ELECT PWR -- GEN DRIVE - IDG SCAVENGE FILTER



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contaminated oil went through it, you do not have to

flush the external oil cooling circuit.

CAUTION: BE SURE FILTER COMPONENTS ARE SEATED IN THE

IDG SCAVENGE FILTER CAVITY BEFORE INSTALLING

FILTER COVER. DO NOT FORCE FILTER COMPONENTS

INTO HOUSING BY TIGHTENING FILTER COVER.

- 176 -

747 TRAINING MANUAL

SCAVENGE



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ELECT PWR - GEN DRIVE - IDG SCAVENGE FILTER

SCAVENGE

"O" RING

USUAL (RESET)OUT

"O" RING

DELTA PINDICATOR

RED BUTTON RED BUTTON

FILTER

FILTER

FWD

- 177 -



747 TRAINING MANUAL

ACCESSORY

LOCKWIRE

GEARBOX



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ELECT PWR - GEN DRIVE - IDG REMOVAL AND INSTALLATION

QAD RING AND

LOCKWIRE

TENSION

ALIGNMENT MARKS

QAD TENSION

ADAPTER PLATE

BOLT

(CLOSED POSITION)

BOLT

- 179 -

747 TRAINING MANUAL

General

These supply power for airplane dc power:

- Main battery - forward-right main equipment center

- Main battery charger - forward-right main

equipment center, E30-2

- Transformer rectifier units (TRU) (4) - forward-

right main equipment center, E30-2

- APU battery - aft equipment center, E33-2

- APU battery charger - aft equipment center, E33-1.

ELECT PWR -- DC GENERATION - INTRODUCTION



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- 180 -

747 TRAINING MANUAL

APU BATTERY

APU BATTERY CHARGER



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ELECT PWR - DC GENERATION - INTRODUCTION

TRU(S)

MAIN MAINBATTERY

CHARGER

BATTERY

- 181 -

747 TRAINING MANUAL

Power Components

The dc power system components are in the MEC, flight

deck and in the aft equipment center. The dc power

system includes:

- TR Units (4)


- Remote Control Circuit Breakers

- Battery Chargers (2)

- DC Current Sensors (6)

- Batteries (2)

- APU TR Unit.

ELECT PWR -- DC GENERATION - DC POWER COMPONENTS



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- 182 -

747 TRAINING MANUAL

ELECTRICAL SYSTEM

BATTERY (2)

DCCS (6)

CONTROL PANEL (P5)



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ELECT PWR - DC GENERATION - DC POWER COMPONENTS

TRU

APU TRUBATTERY

RCCB(4)

CHARGER (2)

- 183 -

747 TRAINING MANUAL


ELECT PWR -- DC GENERATION - DC POWER SYSTEM



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- 184 -

747 TRAINING MANUAL


General

The dc power system supplies and distributes 24/28

volts dc to the airplane. These supply dc power to the

system:

- 75 ampere TRUs (4)

- 24 volt 40 amp-hr batteries (2)

- Battery chargers (2).

These are the dc buses:

- DC buses 1, 2, 3, and 4

- Main hot battery bus- APU hot battery bus

- Main battery bus

ampere TRU and keeps a constant potential on the main

hot battery bus.

APU Hot Battery Bus

The APU hot battery bus gets power from the APU battery

and the APU battery charger. Under some conditions, the

APU battery charger operates as a 64 ampere TRU and

keeps a constant potential on the APU hot battery bus.

Main Battery Bus

The main battery bus gets power through RCCBs from two

possible power sources, the dc bus 3 source or the mainhot battery bus source. Under usual conditions, dc bus

3 gives power to the main battery bus through the



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Main battery bus

- APU battery bus.

DC Buses

The four dc buses get power from four 75 ampere TRUs.

DC current sensors (DCCSs) monitor current from the

TRUs. Each dc bus can be in parallel with the othersthrough the contacts of a dc isolation relay (DCIR).

The DCIRs open and close by the bus tie switches on the

P5 electrical system control panel.

Main Hot Battery Bus

The main hot battery bus gets power from the main

battery and the main battery charger. Under some

conditions, the main battery charger operates as a 64

3 gives power to the main battery bus through the

contacts of the energized battery transfer relay. If

the dc bus 3 source loses power, the battery transfer

relay deenergizes and the main battery relay energizes.

The main hot battery bus then gives power to the main

battery bus.

APU Battery Bus

The APU battery bus gets power through RCCBs from three

possible power sources; the dc bus 3 source, APU hot

battery bus source, or the main hot battery bus source.

Under usual conditions, dc bus 3 gives power to the APU

battery bus through the contacts of the energized

battery transfer relay. If dc bus 3 loses power, the

battery transfer relay deenergizes and the main battery

relay energizes. The APU hot battery bus then givespowers to the APU battery bus.

- 185 -

747 TRAINING MANUAL


The APU battery bus can also get power from the main

hot battery bus. During an APU start on an airplane

with no power, the APU transfer relay energizes and

connects the main hot battery bus to the APU battery

bus. This is to make sure that the decrease in voltage

on the APU hot battery bus (caused by the APU startermotor) does not have an effect on the APU control

circuits on the APU battery bus.



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- 186 -

747 TRAINING MANUAL

INVERTER

DCCS

DCIR

DC

DC BUS 3

TRUTRUTRU

APU BATXFER RLY BUS XFR

2 3LOADS

APU HOT BAT BUSAPU

DCCS APU BATCHARGER

BATAPU BAT BUS

RCCB

1

DCCS

DCIR

DC

DC BUS 2

LOADS

RCCB

DCCS

DCIR

DC

DC BUS 1

LOADS

RCCB

TRU4

DCCS

DCIR

DC

DC BUS 4

LOADS



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ELECT PWR - DC GENERATION - DC POWER SYSTEM

APU STAT

TO APU

RCCB

MAIN HOT BAT BUSMAIN

DCCS MAIN BAT

TO AC

STATIC

MAIN BATBAT RLY

INVERTER

XFR RLY

CHARGER

BAT

INVERTER

XFER RLY

STANDBY BUS

BUS XFRRELAY

STANDBY BUS

CHARGER

RCCB

RCCB

RCCB

MAIN BAT BUS

RCCB

- 187 -

747 TRAINING MANUAL

General

The controls for the dc system are on the electrical

system control panel in the flight deck. These controls

are the battery switch, bus tie switches and standby

power switch.

Battery Switch

The battery switch is a latch type switch; push in

(latched on), push out (latched off). With the battery

switch latched in the ON light in the switch comes on.

With the battery switch out the OFF light comes on.

Bus Tie Switch

Operation to the latched in position enables automatic

ELECT PWR -- DC GENERATION - DC CONTROL



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Operation to the latched in position enables automatic

operation of the bus tie breaker and the dc isolation

relay. Operation to the out position opens the BTB and

the dc isolation relay.

Standby Power Switch

The standby power switch is a rotary-type, three-

position switch. With the switch in AUTO or OFF the hot

battery bus sources give power to their related battery

buses only with a loss of power from the dc bus 3

source. If you put the switch to BAT, the hot battery

bus sources give power to their related battery buses.

- 188 -

747 TRAINING MANUAL

wAUTO

ISLNa

BUS

TIEw

AUTO

ISLNa

wAUTO

ISLNa

wAUTO

ISLNa

L - UTILITY - R

EXT PWR 1 APU GEN 1

ON

OFF

BATTERY

ONw

a

w w

AVAIL

OFF

ONw

a

OFF

ONw

aON

w

AVAIL

ON

w w

AVAIL

ON

w

AVAIL

APU GEN 2 EXT PWR 2

APU

ONOFF STARTBAT

AUTOOFF

STANDBY POWER



24-30-00

2 4 - 3

0 - 0 0 - 0 0 3

R e v

1

1 0 / 2 6 / 1 9 9 9


ELECT PWR - DC GENERATION - DC CONTROL

ELECTRICAL SYSTEM CONTROL PANEL (P5)

DRIVE

w

a

w

a

ON

OFF

1 32

GEN

CONT

DRIVE

DISC

BUS

DRIVE

w

a

w

a

ON

OFF

BUS

DRIVE

w

a

w

a

ON

OFF

BUS

DRIVE

w

a

w

a

ON

OFF

BUS

4

- 189 -

747 TRAINING MANUAL

General

There are four inter-changeable 75 ampere TRUs on the

E30-2 equipment shelf in the forward right main

equipment center. All are static devices change three-

phase, ac power into 28 volts dc power for the dcbuses.

Forced air cooling is necessary when the TRUs supply

maximum output current. The units can operate at 25% to

30% of their maximum current with convection cooling

only.

ELECT PWR -- TRANSFORMER RECTIFIER UNITS - INTRODUCTION



24-32-00 2 4 - 3 2 - 0 0 - 0 0 1

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- 190 -

747 TRAINING MANUAL

P180 DCDISTRIBUTIONPANEL



24-32-00

2 4 - 3

2 - 0 0 - 0 0 1

R e v

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1 0 / 2 8 / 1 9 9 9


ELECT PWR - TRANSFORMER RECTIFIER UNITS - INTRODUCTION

FWD

INBD

E30

NOSE GEAR

TRU 1, 2,

EQUIPMENTRACK

WHEEL WELL

3 & 4

- 191 -

747 TRAINING MANUAL

General

A DCCS is an electronic unit that senses dc current.

The DCCSs are in six locations in the airplane dc

system:

- Four in the P180 to monitor TRU output current

- One at the main battery to monitor main battery

current

- One at the APU battery to monitor APU battery

current.

Function

The DCCSs do these functions:

Gi TRU t d t t th GCU d BCU f

DC CURRENT SENSORS (DCCS) --



24-34-00 2 4 - 3 4 - 0 0 - 0 0 1

R e v

1

1 0 / 0 1 / 1 9 9 9


- Gives TRU current data to the GCUs and BCUs for

indication on the EICAS maintenance page

- Gives TRU current data to the GCUs and BCUs for TRU

malfunction indication on EICAS and triple channel

autoland operation

- Gives battery current data to the BCUs for

indication on the EICAS maintenance page andbattery discharge indication at an advisory level

on EICAS.

- 192 -

747 TRAINING MANUAL

(4) (1)

P180 DC AFT

APU

CLOSET

DISTRIBUTIONPANEL

BATTERY

LEFTDOOR 5



24-34-00

2 4 - 3

4 - 0 0 - 0 0 1

R e v

1

1 0 / 0 7 / 1 9 9 9


DC CURRENT SENSORS (DCCS)

FWD

INBD

FWDINBD

(1)

NOSE GEAR

MAIN

CLOSET

WHEEL WELL

BATTERY

- 193 -

747 TRAINING MANUAL

General

Remote control circuit breakers (RCCB) are in P180 and

P183. The RCCB is a circuit breaker that uses a remote

1/2 ampere circuit breaker for control and indication.

The 1/2 ampere circuit breakers are in the flight deck.When the RCCB senses an overload, it opens the circuit

internally and opens the breaker in the flight deck.

You push in the flight deck circuit breaker to reset

the RCCB. The physical position of the RCCB shows in a

window on it as a red flag (closed) or a green flag

(open).

ELECT PWR -- AC ELECT LOAD DISTRIBUTION - REMOTE CONTROL CIRCUIT BREAKERS



24-50-00 2 4 - 5 0 -

0 0 - 0 0 2

R e v

1

1 0 / 2 8 / 1 9 9 9


- 194 -

747 TRAINING MANUAL

P180 DC

E30

P183

DISTRIBUTIONPANEL

DISTRIBUTIONPANEL



24-50-00

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0 - 0 0 - 0 0 2

R e v

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ELECT PWR - AC ELECT LOAD DISTRIBUTION - REMOTE CONTROL CIRCUIT BREAKERS

RCCB

POWER LOAD

DOORGREEN (OPEN)

(P6)

RED (CLOSED) 5L

- 195 -

747 TRAINING MANUAL

General

The four dc buses get power from four 75 ampere TRUs.

The GCUs monitor voltage and current from the TRUs.

Each TRU can be in parallel with the others through the

contacts of a dc isolation relay (DCIR). The DCIRs openand close with the bus tie switches (P5).

DC Bus Power

The dc buses can get power from their related TRU or

from the other TRUs through the dc isolation relays.

Each TRU gets 3-phase, 400 Hz, 115 volts ac power from

its ac load bus. The TRU changes the 115 volts ac to 28

volts dc.

DCIR Control

ELECT PWR -- DC GENERATION - DC BUS CONTROL



24-30-00 2 4 - 3 0 -

0 0 - 0 0 5

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1

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Each DCIR gets manual control from its related bus tie

switch in the flight deck or automatic control from its

related GCU when there is an autoland mode request.

With the bus tie switch in the isolation position 28

volts goes to energize the DCIR. This isolates the dcbus.

When the GCU gets an autoland request from the BCUs and

3 or more IDGs are available, the GCU energizes the

DCIR and isolates the dc bus. The two BCUs monitor the

auxiliary contacts of the DCIRs for an indication of dc

bus isolation.

- 196 -

747 TRAINING MANUAL

DCCS

TO OTHER

TO

RCCB

R7219 DC

EIU

BCU 2

BCU 1TRU 1

DC BUS 1

+28V DC

AUTO

BUS TIE SW (P5)

P6

TRANSFORMER

115V AC

ISLN

BUS 1

RECTIFIERUNIT 1

(E30-2) (P180)

(P180)

DC LOADS

ISOLATION(P180)

DCIR



24-30-00

2 4 - 3

0 - 0 0 - 0 0 5

R e v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - DC GENERATION - DC BUS CONTROL

+28V DC

BCU 1

NOTE: SYS 1 SHOWNTRU 2, 3, AND 4 SIMILAR

GCU 1

3 IDGS

3 IDGS

AUTOLAND MODEAVAILABLEBCU 1

AVAILABLEBCU 2

- 197 -

747 TRAINING MANUAL

General

To find if a TRU has a malfunction the GCU first does a

check to see if the DCIR is open or closed.

If the DCIR is open (dc bus isolated), the GCU looks atthe dc bus voltage to find if it is less than 18 volts

and TRU current is less than 2.5 amperes.

If the DCIR is closed, the GCU only looks at TRU

current to find if it is less than 2.5 amperes. It does

not look at dc bus voltage because the voltage on the

bus could be from a different TRU.

When one of these two conditions is true and therelated ac bus has power and the DCCS is in operation,

a digital TRU fail signal goes to BCU 1 and 2. BCU 1

(BCU 2 if BCU 1 has a malfunction) causes ELECT TR UNIT

ELECT PWR -- TRANSFORMER RECTIFIER UNITS - FAILURE INDICATION



24-32-00 2 4 - 3 2 -

0 0 - 0 0 3

R e v

1

1 0 / 2 8 / 1 9 9 9


to show on the EICAS status page. This message shows

that the TRU has a malfunction.

- 198 -

747 TRAINING MANUAL

TRU 1 DCCS

ELEC TR UNIT 1

DC BUS 1

EIU

TRU 1

TRU DC VOLTS <18

DC CURRENT <2.5

DCIR OPEN

(E30-2) (P180)VOLTAGE(P180)

VOLTAGECURRENT



24-32-00

2 4 - 3 2 - 0 0 - 0 0 3

R e v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - TRANSFORMER RECTIFIER UNITS - FAILURE INDICATION

EICAS STATUS PAGE

GCU 1

NOTE: TRU 1 SHOWN

BCUBCU1 2

TRU FAILED

FROM

DCIR CLOSED

AC BUS 1 POWERED

DCCS NOT FAILEDOTHER GCU(S)

TRU 2, 3, AND 4

SIMILAR

- 199 -

747 TRAINING MANUAL

General

The main and APU battery buses usually get power from

dc bus 3 through the contacts of the energized battery

transfer relay (R7224). If a condition occurs that

deenergizes the battery transfer relay, the mainbattery relay energizes. This connects the main and APU

battery buses to their related hot battery buses for dc

standby power.

Battery Transfer Relay

Power from dc bus 3 energizes the battery transfer

relay. The power goes through the contacts of the

energized dc voltage sense relay (R7228) and thecontacts of the deenergized single TRU operation relay

(R7225). The battery transfer relay deenergizes when:

P i l t f d b 3

APU Battery Bus Transfer Relay

During an APU start the APU battery bus transfer relay

(R7687) energizes. If the main battery relay energizes

(such as on an airplane with no power), the main hot

battery bus connects to the APU battery bus. This isdone to make sure that the decrease in voltage on the

APU hot battery sources (caused by the APU starter

motor) does not have an effect on the APU control

circuits on the APU battery bus.

ELECT PWR -- BATTERIES - MAIN/APU BATTERY BUS POWER



24-31-00 2 4 - 3 1 -

0 0 - 0 1 0

R e v

1

1 0 / 2 8 / 1 9 9 9


- Power is lost from dc bus 3 sources

- The standby power switch is in the BAT position

(this causes the dc voltage senses relay to

deenergize and remove power from R7224)

- The single TRU operation relay energizes (if one

of the two BCUs sense only one TRU in operation,R7225 energizes and removes power from R7224).

Main Battery Relay

The main battery relay (R7223) gets power from the main

hot battery bus sources. With the battery switch on and

the battery transfer relay deenergized the main battery

relay energizes and connects the main and APU hot

battery buses to their related battery buses.

- 200 -



747 TRAINING MANUAL

General

The BCUs use the single TRU operation relay (R7225) to

control the battery transfer relay (R7224). When one of

the two BCUs sense that only one TRU is in operation,

the single TRU operation relay energizes. Thisdeenergizes the battery transfer relay and removes the

main and APU battery bus loads from the one TRU.

Operation

The DCCSs sense the current output of the four TRUs.

This data goes to the related GCU. If the GCU finds

that the output of the TRU is less than 2.5 amperes, it

sends a TRU fail signal to the BCUs. When one of the twoBCUs find that only one TRU is in operation, the single

TRU operating relay energizes.

ELECT PWR -- TRANSFORMER RECTIFIER UNITS - SINGLE TRU OPERATION



24-32-00 2 4 - 3 2 -

0 0 - 0 0 2

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1

1 0 / 2 8 / 1 9 9 9


- 202 -

747 TRAINING MANUAL

TRU TRU FAIL

TRU

DCCSARINC

GCU 1

ARINCSINGLE

TRU FAIL

GCU 2 GCU 3 GCU 4

FAILLOGIC

429XMITTER

429RECEIV

TRU

DC BUS 1

DC BUS 3



24-32-00

2 4 -

3 2 - 0 0 - 0 0 2

R e v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - TRANSFORMER RECTIFIER UNITS - SINGLE TRU OPERATION

R7228 DC

R7225 SINGLE

R7224

BCU 2

BCU 1 VOLTAGESENSE (P6)

TRU OPERATION

(P180)

BAT. XFR(P180)

RECEIV-ERS

LOGICDC BUS 3

- 203 -



747 TRAINING MANUAL

R7219 - R7222

DC CURRENT

P180

RCCB

RCCB

DC ISOLATIONRELAYS

SENSORS

P180 DC

FWD

DISTRIBUTIONPANEL



24-30-00

2 4 -

3 0 - 0 0 - 0 0 4

R e v

1

1 0 / 2 8 / 1 9 9 9


ELECT PWR - DC GENERATION - P180 INSTALLATION

OPTIONAL BATTERY OR

OPTIONAL BATTERY POWERED

P180-1 DC

R7224 BATR1195 TOWING

R8154 TOWING

R7223 MAIN

R7225 SINGLE TRU

R7687 APU BAT

DISTRIBUTION PANEL

BUS XFER RELAY

POWER XFER

TOWING BUS

GHB POWERED TOWING BUS OPERATION RELAY

GHB/BAT XFERCONT

XFER RELAY

BAT RELAY

1

2

2

1

- 205 -

747 TRAINING MANUAL

General

The main battery is in the forward right main equipment

center. The APU battery is aft of the 5L door on the

E33-2 equipment rack. These are 40 amp-hr, 24 volt dc

nickel-cadmium batteries. Natural convection removesheat from these batteries. They have a vent into the

related equipment center. Each battery has:

- case

- cover

- twenty cell assemblies

- temperature sensor assembly.

The sensor assembly includes a thermoswitch and acharge control thermistor. The thermoswitch removes

power to the battery charger if the battery temperature

goes above safe operation limits. The charge control

thermistor gives a signal to the battery charger to

ELECT PWR -- BATTERIES - MAIN/APU BATTERY



24-31-00 2 4 - 3 1 - 0 0 - 0 0 1

R e v

1

1 0 / 2 6 / 1 9 9 9


control the charge in relation to the battery

temperature.

The APU battery ground is a dual ground configuration

connection connected to a bracket on the airframe.Other electrical components in the aft equipment center

having similar connections are the APU battery charger

and TRU.

NOTE: To prevent possible arcing or overheating at the

ground, maintenance procedures require these

connections be properly torqued.

- 206 -

747 TRAINING MANUAL

APU BATTERY(E33-2 RACK)

APU TRU

APU BATTERYCHARGER SEEPANEL

DISTRIBUTIONP180 DC

RACKEQUIPMENTE30

DUAL GROUNDCONFIGURATION(TYPICAL)

WIRE

LUG

BRACKET

DUAL GROUND

A

A



24-31-00

2 4 -

3 1 - 0 0 - 0 0 1

R e v

1

1 0 / 0 9 / 2 0 0 0


ELECT PWR - BATTERIES - MAIN/APU BATTERY

NO. 5L MAINENTRY DOOR

AFT EQUIPMENT CENTER (E8)

BATTERYMAIN

INBD FWD

WHEEL WELLNOSE GEAR

FWD

INBD

- 207 -

747 TRAINING MANUAL

General

The main battery charger is on the E30-2 shelf in the

forward right main equipment center. The APU battery

charger is aft of the 5L door on the E33-1 equipment

rack. These chargers have two different functions. Theygive a dc output to charge the related battery and

operate as a TRU during some conditions.

The battery chargers get forced air cooling and are

inter-changeable. AC power for the charger comes from

the ground service bus.

Charge Mode

In the charge mode, the battery charger starts the

battery charge cycle in the constant current mode (38

amperes). As the battery charges, the output voltage

increases with the battery condition of charge and load

i t At th t t it i 28 lt d ith th

TR Mode

In the TR mode, the charger supplies a constant 27.75v

dc up to 64 amperes. This voltage keeps the battery

charge with minimum electrolyte loss.

Charger Off

The battery charger goes off for these conditions:

- Battery connector off when power connected

- Battery interlock open (small connector off)

- Overcurrent (internal fault)

- Battery overtemperature

- Loss of input power- Input ac voltage more than 134 volts or less than

94 volts.

ELECT PWR -- BATTERIES - MAIN/APU BATTERY CHARGER



24-31-00 2 4 - 3 1

- 0 0 - 0 0 2

R e v

1

0 1 / 1 5 / 2 0 0 1


resistance. At the start, it is 28 volts dc with the

current at 38 amperes. As the battery charge increases,

the output voltage increases until it gets to the

inflection voltage. The inflection voltage changes with

battery temperature but is 31v dc at normal ambienttemperatures. At the inflection voltage, the battery

voltage continues to increase during an overcharge

period. The quantity of overcharge is percentage (12%)

of the time necessary for the battery to get to the

inflection voltage. The battery charger then changes to

the constant potential mode of 27.75 volts dc. In the

constant potential mode, there is a current limit of 38

amperes.

- 208 -



747 TRAINING MANUAL

Operational Test

The following is a battery charger test for the APU

battery charger: (Main battery charger test is

similar.)

- Proper operation of an APU battery charger can be

verified by observing a charge cycle. A new charge

cycle is initiated when input power is removed for

more than 500 MSEC and then reapplied. When an APU

battery is replaced, the charge cycle will be

initiated by the opening and closing of circuit

breaker /APU BAT CHGR/ on the P183 panel. On the

EICAS ELEC MAINTENANCE page, the APU BAT current

will indicate /CHG/ with 31 to 43 AMPS. APU batteryvoltage will start at 27 to 29 volts, rise to 31

volts as the battery state of charge increases,

then drop to 28 volts. When the voltage drops to 28

volts, the current also reduces to /CHG/ or /DIS/

of 0 to 5 amps

minimum battery voltage is 4 volts dc to initiate the

charge cycle.

Charger Off

The battery charger turns off under the followingconditions:

- Battery connector off when power applied

- Battery interlock open (small connector off)

- Overcurrent (internal fault)

- Battery over temperature

- Loss of input power

- Input ac voltage over 134 volts or under 94 volts.

ELECT PWR -- BATTERIES - BATTERY CHARGER CHARGE MODE



24-31-00 2 4 - 3 1

- 0 0 - 0 1 1

R e v

1

1 0 / 0 1 / 1 9 9 9


of 0 to 5 amps.

NOTE: The state of charge of a nickel-cadmium battery

cannot be determined by measurement of battery

voltage. With the exception of dead batteries,the voltage at both open circuit and under load

conditions do not significantly vary with respect

to state of charge. The only dependable method to

determine a battery's state of charge is through

a measured complete discharge.

The battery charger is capable of fully recharging a

battery within a 75 minute time period, provided the

- 210 -



747 TRAINING MANUAL


ELECT PWR -- BATTERIES - MAIN HOT BATTERY BUS POWER



24-31-00 2 4 - 3 1

- 0 0 - 0 0 5

R e v

1

1 0 / 2 6 / 1 9 9 9


- 212 -



747 TRAINING MANUAL

ELECT PWR -- BATTERIES - MAIN HOT BATTERY BUS POWER

in the MEC. For this condition the battery charger does

not go into the constant current charge mode so that it

does not release gas into the MEC.

Charger Failed

A charger malfunction signal goes to BCU 1 when:

- The interlock opens (small connector off)

- The battery temperature is more than 63C

- There is no input power.

NOTE: The battery charger does not turn on unless the

battery voltage is above 4 volts when power is

first applied to the battery charger.



24-31-00 2 4 - 3 1

- 0 0 - 0 0 5

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1

1 0 / 2 6 / 1 9 9 9


- 214 -



747 TRAINING MANUAL


ELECT PWR -- BATTERIES - APU HOT BATTERY BUS POWER



24-31-00 2 4 - 3 1 - 0 0 - 0 0 6

R e v

1

1 0 / 2 6 / 1 9 9 9


- 216 -



747 TRAINING MANUAL

ELECT PWR -- BATTERIES - APU HOT BATTERY BUS POWER

deenergizes, or the two primary and secondary

lavatory/galley vent control relays deenergize. When

the battery transfer relay deenergizes, or the APU

inverter relay energizes, the higher current limit is

available to supply the APU battery bus loads. If the

two lavatory/galley vent control relays deenergize, thebattery charger does not go into the constant current

charge mode so that it does not release gas around the

battery.

Charger Failed

A charger malfunction signal goes to BCU 2 when the:

- Interlock opens (small connector off)- Battery temperature is more than 63 C

- Input power is removed.

NOTE: The battery charger does not come on unless the

battery voltage is above 4 volts when power is

first connected to the battery charger



24-31-00 2 4 - 3 1 - 0 0 - 0 0 6

R e v

1

1 0 / 2 6 / 1 9 9 9


first connected to the battery charger.

- 218 -

747 TRAINING MANUAL

APU BAT

R7498 PRI LAV-GLY

R1434 APU INV

APU BAT

R7218 APU BATP183

28V DC APU

115V AC

APU HOT

- LOSS OF POWER- BAT TEMP >63C- CONNECTOR OFF BAT CHARGER

CONT

- 28V DC CONSTANT

- 28V DC CONSTANT

- 38A CONSTANT

APU BAT

P183

DC

RCCB

GSB XFR

CHARGER

OVHT PROT

(P183)

XFR (P183)

VENT CONT (E8)

CUR CHARGE

POTENTIAL 38A

POTENTIAL

MALFUNCTION

CHARGEROUTPUT

BAT BUS

(P183)

LOADS

TO BCU 2

LIMIT

64A LIMIT

HOT BAT BUS

R7188 APUSTART (P83)

1

CHARGER DISABLE



24-31-00

2 4

- 3 1 - 0 0 - 0 0 6

R e v

1

1 0 / 2 6 / 1 9 9 9


ELECT PWR - BATTERIES - APU HOT BATTERY BUS POWER

DCCS

STANDBY PWR SW (P5)

OFF

AUTO

BAT

TO

T

-

+

APU BATTERY

69C59C

INTER-

BCU 2

LOCK

APU BAT CHARGER(E33-2)

R7224 BAT XFR (P180)

R7498 SEC LAV-GLYVENT CONT (E8)

1 ENERGIZED DURING APU START

- 219 -



747 TRAINING MANUAL

60 SEC

BAT TEMP

OPEN = 1

BAT CHARGER MAINCHARGER

AUTOOFF

BAT

STANDBY PWR

BATTERY CHARGER

INTERLOCK OPEN

LOSS OF

BAT CHARGER APU

SW (P5)

TD

>63C

INPUT PWR

MALFUNCTIONARINC429XMTR



24-31-00

2 4

- 3 1 - 0 0 - 0 0 7

R e v

1

1 0 / 1 6 / 2 0 0 0


ELECT PWR - BATTERIES - MAIN/APU BATTERY CHARGER FAILURE INDICATION

EIU

EICAS STATUS PAGE

GSB

- MAIN BATTERY CHARGER - BCU 1

BCU

- APU BATTERY CHARGER - BCU 2

TD

POWERED

- 221 -

747 TRAINING MANUAL

General

A DCCS senses battery current. This sensor is on the

battery ground wire adjacent to the battery. Current

data from this sensor goes to BCU 1 for the main

battery and BCU 2 for the APU battery. When the BCU

finds a battery discharge of two amperes or more, it

tells the EIUs to show the advisory message BAT DISCH

APU or BAT DISCH MAIN. Logic circuits in the EIUs make

the decision when to show the messages. This includes

an APU start inhibit for BAT DISCH APU and possible

time delays necessary for the message.

ELECT PWR -- BATTERIES - MAIN/APU BATTERY DISCHARGE INDICATION



24-31-00 2 4 - 3

1 - 0 0 - 0 0 8

R e v

1

1 0 / 2 8 / 1 9 9 9


- 222 -



O Æ

致獨鐘 ~

MAINTENANCE

TRAINING

M NU L

APU

TRU

The

APU t r ansformer

r e c t i f i e r

un i t

TRU)

i s an l t e r n dc power source

for

s t a r t i n g

the APU.

The un i t

cons i s t s

of a

cool ing

fan ,

power

t r ansformer

, thermal

switches and

two

three phase f u l l wave

r ec t i f i e r s .

The

TRU produces 28 vo l t s dc from

an

input

h r e e p h s e

400

Hz

,

115

vo l t s

ac.

The TRU i s in the e q u i p m e n t cen te r .



747

FEB 11/93

--\

24.32.504.003

AGE

2

PAGE 223A

AFT LEFT

DOOR

5

E33-1

EQUIPMENT

R CK

~

NEGATIVE

C

POSITIVE

C

INBD ~

UNITECTIFIER

R N S F O R

PU



24.32 .004 .003

PAGE

275

APU TRU

747

JAN 05/93 PAGE 223B

O Æ

W 間

MAINTENANCE

TRAINING

M NU L

APU TRU

POWER

The APU TRU i s used for APU s t a r t i n g

power when the

APU s t a r t

source swi tch

on

P461

i s in

TR

dur ing an APU s t a r t .

AC power

for

the

APU

TRU

i s

suppl ied

from AC

Bus

4 th ru t he

u t i l i t y

ELCU 4 ,

and t he r i gh t u t i l i t y swi tch

placed

in

t he ON

l l l



747

AUG 13/97 PAGE 223C

24.32.506.002

PAGE

276

\

--\

\

E33-1)

TRU

R700

GALLEY/

TRU

XFER P30)

APU

SW

RIGHT

UTILITY

APU

SOURCE

BATTERY

@

APU

ON

O?@ RT

APU



ELCU

4

P5

24.32.006.002

PAGE 277

POW R

PU TRU

29/97

PAGE 223D

747

AUG

H Æ W 唔 ~

I N T E N N E

TRAINING

M NU L



747

SEP 10/87 PAGE 223E

r:

( ì

00.00.001.

001

PAGE

278

r .

H D ~ w ~ 7

MAINTENANCE

TRAINING

M NU L

APU TRU OPERATION

旦旦旦旦主主

The

APU

TRU

i s

in the a f t e q u i p m e n

cen te r on

the

she l f . Three-phase

115 ac

power i s suppl ied to the

TRU from

the

u t i l i t y ELCU in P414.

Wh

en us ing the TRU

to

s t a r t the

APU ,

power

i s

t r ans fer red

f r o m h e u t i l i

Y

bus

to the APU TRU. with power

app l i ed

the TRU supp l i e s 28 vo l t s dc d i r e c t l y

to

the APU s t a r t e r

motor.

To

APU TRU

for s t a r t i n g the

APU , power must be ava i l ab le on the GSB

and on main ac bus No. 4

,

and

the

r i gh t

u t i l i t y bus switch

la tched

on.

TRU s t a r t s a re

accomplished by plac ing

APU s t a r t

source

se l ec t

P461)

to

TR

and

ro t a t i ng

the

APU

master

control

s w i t c h START.

During s t a r t with

u t i l i t y

4

power ava i l ab le the

ac

power sense-TRU

APU s t a r t r e l ay R8225) energized.

This arms the t r a n s f e r c i r c u i t .

At

the

same t ime

the

APU-TRU

t rans fe r

re l ay

R8204) i s energized arming

the

APU

s t a r t and TRU

l a t ch

re l ay r c u i t s

With a TRU s t a r t se lec ted

the

APU

TRU

d isab le

r e l ay R8203) i s

also

energized . This

u a l l y

d isab le s the

APU b a t t e r y

c i r c u i t and

ac t iva t es

the APU TRU s t a r t r c u i t

The

galley/TRU

t rans fe r

r e l ay R700)

i s

energized through R8203. This

t r an s f e r s u t i l i t y

4 ga l l ey power to

the

APU

TRU. The output of the APU TRU

i s

c o n n e c d i r e c t l y to

the

APU

s t a r t e r

motor.

Energiz ing

R700 causes the

r e l ay R704) to energize .

connects ground service ac

APU

TRU cool ing

fan.

APU TRU

This

power to the

Wh en

the

APU i s completed, power

i s

t r ans fer red

from

the

TRU back

to the

ga l l ey .

Protec t ion

r i n g an APU TRU

s t a r t the

TRU

cool ing

fan

i s

always r u n n i n g the TRU

tempera ture exceeds 50

o

C

, the

cool ing



747

NOV 28/94 PAGE 223F

fan s tays on un t i l e m p e r a t u r e

lowers.

24.32.505A.002

PAGE 279

Æ 致 W G

M INTEN NCE

TR INING

M NU L

王旦主豆豆且

cont)

the TRU

tempera ture exceeds

12 0

o

C

,

the APU TRU

l a t ch

re l ay R8202) i s

energized . This disarms the APU TRU

c i r c u i t

t r ans fer r ing

s t a r t e r

motor

power

to

the

APU bat t e ry .

R8202

remains

energized as

long

as

the

APU

TRU

tempera ture

i s above

12 0

0

C or the

APU

i s

s ta r t ing .



747

NOV

28/94 PAGE 223G

2 4 . 3 2 . 5 5 B . 0 0 2

PAGE

280

1)

f

DC

PWR

TO APU

STARTER

O T O R

f

f 九

APU

BA

T.

TO

LOAD

APU

TRU

斗

E33-1

OVERHEATRU

PU

120

0

C

訂

已

ι 一 ÷ →

UTIL

B

BUS 4

P414)

28V

DC

BAT.

BUS APU TRU

CONTROL

R8204 APU

TRU

XFR

DURING

江百

午址

1 1



P183)

b i l i R ; ; 需

需可言 : : E

〉

斗

3 2 5 2

PAGE 281

APU TRU

OPERATION

P461)

13/94 PAGE 223H

747

DEC

747 TRAINING MANUAL

General

The ac standby power system gives power to flight

critical loads if there is a loss of airplane

electrical power. The system has these components:

- Transfer relay- AC standby bus

- Static inverter

- Control switch.

The flight critical loads connect to the ac standby

bus, which receives power from ac bus 3 or the static

inverter. Manual control of the static inverter is from

the standby power switch on the electrical system

control panel in the flight compartment.

ELECT PWR -- AC STANDBY PWR GENERATION - INTRODUCTION



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- 224 -

747 TRAINING MANUAL

STANDBY POWER

OFFAUTO

BAT STANDBY POWER

ELECTRICAL SYSTEM

CONTROL

TRANSFER RELAY(P6)

CONTROL PANEL (P5)

AC BUS 3AC STBY



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ELECT PWR - AC STANDBY PWR GENERATION - INTRODUCTION

STATIC INVERTER(E30-2)

- 225 -

747 TRAINING MANUAL

General

The position of the standby power switch causes manual

or automatic control of the ac standby power system.

The static inverter always has power but is not always

on. When it gets an on command, the static inverter

gives power to the ac standby bus.

Automatic Operation

When ac bus 3 has power, and the standby power switch

is in AUTO, the standby power transfer relay energizes.

This connects ac bus 3 to the ac standby bus. Another

set of contacts in the relay puts a ground on the

remote control lead of the static inverter. This keeps

it off. If ac bus 3 loses power, the standby powertransfer relay deenergizes. This connects the ac

standby bus to the output of the static inverter and

removes the ground from the remote control lead. The

static inverter comes on and supplies 115 volts ac

power to the ac standby bus.

Manual Operation

deenergizes and R7223 energizes. This connects the

inverter to the main hot battery bus. The static

inverter then gets power from the battery and gives

power to the ac standby bus.

ELECT PWR -- AC STANDBY PWR GENERATION - OPERATION



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Manual Operation

If you put the standby power switch to OFF, a ground onthe remote control lead keeps the static inverter off.

If you put the standby power switch to BAT, the standby

power relay deenergizes. This causes the static

inverter to come on and moves the inverter's 28 volts

dc input power. Under usual conditions R7224 contacts

are closed. This gives the static inverter power from

dc bus 3. With the standby power switch in BAT R7224

- 226 -

747 TRAINING MANUAL

REMOTE CONTROL

115V AC

M7438 STATIC

115V AC

AC 3 STANDBY

STANDBY

AC STANDBY BUS

28V DC

R7223 MAIN

R7224 BATTERY

MAIN HOT

DC BUS 3

BAT. BUS

BATTERY (P180)

TRANSFER (P180)

INVERTER (E30)

(GND = OFF)

BUS 3

POWER

TRANSFER RELAY



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ELECT PWR - AC STANDBY PWR GENERATION - OPERATION

OFF

AUTO

BAT

STANDBY POWER

P6 R7227 STANDBY

TRANSFER RELAY

SWITCH (P5)

POWER TRANSFER(P6)

- 227 -

747 TRAINING MANUAL

General

The APU static inverter provides power for the left FMC

and the captain's integrated display units (IDU) in the

event of a power loss to the captain's transfer bus.

The output of the static inverter is connected to the

PFD-L, ND-L and the FMC-L through the relaxed contactsof the transfer relay.

NOTE: Circuit diagrams refer to the captain's outboard

IDU as the left primary flight display (PFD-L)

and the captain's inboard IDU as the left

navigation display (ND-L).

ELECT PWR -- AC STANDBY PWR GENERATION - APU STATIC INVERTER POWER



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- 228 -

747 TRAINING MANUAL

CAPT XFER

CAPT PFD-LEFT

APU HOT

TO STANDBYPOWER SW

BAT. BUS

XFER BUS

RELAY (P6)

ND-LEFTFMC-LEFT



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ELECT PWR - AC STANDBY PWR GENERATION - APU STATIC INVERTER POWER

APU STATIC INVERTER

R1434 APU

E8

INV XFR(P183)

POWER SW

(P5)

- 229 -



747 TRAINING MANUAL

APU STATIC

C10680 APU STBY

PFD-L

ND-L

FMC-L

24V DC GND=OFF

APU HOT

CONT

C10416

C10412

CONT

R1434 APU

BAT. SW

BAT.

OFF

AUTO

R7188

R7853

C10415

APU INVRLY PWR

(P183)

APU INVPWR (P183)

BAT. BUS

INV XFER(P183)

INVERTER (E8)

ALT PWR (P6)

APU START(P83)

APU STBY

APU STBYXFR PWR(P6)

(P5)



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ELECT PWR - AC STANDBY PWR GENERATION - APU BATTERY STBY PWR - OPERATION

CAPT XFER BUS

AC BUS 3

AC BUS 1IBVSU

STANDBY POWERSWITCH (P5)

BUS XFER(P6)

- 231 -

747 TRAINING MANUAL

General

Two instrument bus voltage sense units (IBVSU) in P6

provide automatic transfer of the captain's and first

officer's flight instrument transfer buses. The IBVSUs

transfer the associated flight instrument transfer

buses from their primary source to ac bus No. 1 if theprimary source voltage drops below 97 volts for 180 ms.

The instrument buses primary sources are ac bus No. 2

for the first officer and ac bus No. 3 for the captain.

Return to the primary source takes place when the

primary source recovers to 106 volts for 1.2 seconds.

Control power for the IBVSUs comes from dc bus No. 1.

If this control power is lost for 20 ms or longer, the

associated IBVSU remains in or returns to its primary

position.

ELECT PWR -- AC PWR DISTRIBUTION - INSTRUMENT BUS VOLTAGE SENSE UNITS



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- 232 -

747 TRAINING MANUAL

LOW

LOW

AC-F/O XFR

POWER

M7508 (P6)

POWER

P6

CAPT XFER

28V DC

F/O XFER

28V DC

AC 1

AC 2

AC-CAPT XFRAC 3

BUS 1

BUS CONT

BUS 1

BUS CONT

SUPPLY

VOLTAGESENSING

SUPPLY



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ELECT PWR - AC PWR DISTRIBUTION - INSTRUMENT BUS VOLTAGE SENSE UNITS

LOW

M7507 (P6)

VOLTAGESENSING

- 233 -

747 TRAINING MANUAL

General

The basic electrical power distribution system has

power control components and functions that aid the

basic electrical power system. These include:

- Electrical load control units (ELCUs) that controlpower to the galleys and utility buses

- Autoland isolation that gives automatic bus

isolation during autoland operations.

ELECT PWR -- AC ELECT LOAD DISTRIBUTION - INTRODUCTION



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- 234 -

747 TRAINING MANUAL

AUTOLANDISOLATION

DISTRIBUTION

ELCU



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ELECT PWR - AC ELECT LOAD DISTRIBUTION - INTRODUCTION

LOADMANAGEMENT

- 235 -

747 TRAINING MANUAL

General

There are eight ELCUs used for load distribution. Two

each are in P514, P614, P515, and P615. Four are used

for the galleys and four for the utility load buses.

Each ELCU has internal circuits for control and

indication and for differential fault and overcurrentprotection.

ELECTRICAL LOAD CONTROL UNIT (ELCU) --



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- 236 -

747 TRAINING MANUAL

P614P514

P615

P515

UTILITY

GALLEY

AC BUS

ELCU

ELCU



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ELECTRICAL LOAD CONTROL UNIT (ELCU)

- 237 -



747 TRAINING MANUAL

FROM

O

S

POWER

S

P5

KVA

AC BUS LOAD

R

OVER CURRENT DIFF FAULT

BCU 1 OR BCU 2

28V DC

ELCU

UTILITY

OFF

RL

OFF

ONON

JUMPER

LOADCT(S)

POSITIONTO BOTHBCU(S)

FROMBCU 1(BCU 2)

PROTECTION PROTECTION

SUPPLY



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ELCU OPERATION

BCU 2

P180

DC BUS

TO BCU(S) FOR

ELCU

ELCU CONTROL(BCU 1)

POWER

- 239 -

747 TRAINING MANUAL


LOAD MANAGEMENT SYSTEM --




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- 240 -

747 TRAINING MANUAL


General

The load management system automatically disconnects

and connects the galley and utility loads. When the

system senses an overload condition because demand is

more than capacity, the system opens and closes ELCUs.

Load Shed

During an overload condition, the load management

system opens the applicable galley ELCUs one at a time

in one-second intervals until the overload condition

goes away. The galley load shed is in this order:

- G ELCU 1- G ELCU 4

- G ELCU 2

- G ELCU 3.

If the overload condition stays after all the galleys

disconnect, load shed continues in one-second intervals

with the utility ELCUs until the overload goes away.

The utility load shed is in this order:

an overload occurs on the remaining paralleled

generators, this is the trip sequence:

- G ELCU 1

- G ELCU 4

- G ELCU 3- U ELCU 1

- U ELCU 4

- U ELCU 3.

Load Restoration

Load restoration occurs in the opposite order as load

capacity increases. This is the order of load

restoration:

- One or no generators - no load restoration

- Two generators - restoration of utility loads and

G ELCU 3

- Three or four generators - restoration of all

loads.

Load restoration for APU and external power occurs as

l d it i



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- U ELCU 1

- U ELCU 4

- U ELCU 2

- U ELCU 3.

When a generator is isolated (BTB open), and there is

an overload on the remaining generators, load shed

starts with the lowest numbered G ELCU or U ELCU if all

the galleys are off. For example, if BTB 2 is open, and

load capacity increases.

IDG Load Management

Generator load sense is from current transformers (CTs)

in the IDGs. The current sensed by these CTs goes to

their applicable GCUs. The GCUs send generator load

data to the BCUs by two paths, an ARINC 429 bus and

hard-wire. The hard-wire signals are redundant and are

for backup if there is a failure of the ARINC 429 bus.

- 241 -

747 TRAINING MANUALLOAD MANAGEMENT SYSTEM --

Normally closed relays are in the BCUs that supply

power and grounds to the ELCUs. BCU 1 gives power to G

ELCU 1 and 2 and to U ELCU 1 and 2. BCU 1 gives a ground

to G ELCU 3 and 4 and to U ELCU 3 and 4.

BCU 2 gives power to G ELCU 3 and 4 and to U ELCU 3 and

4. BCU 2 gives a ground to G ELCU 1 and 2 and to U ELCU1 and 2.



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- 242 -

747 TRAINING MANUAL

0

APU GEN 2

LOAD

POWER 28V DC

BCU 1

G ELCU 3

G ELCU 2

G ELCU 4

U ELCU 1

U ELCU 4

GCU 3

G ELCU 1

APU GEN 1

UTILITY

RIGHTLEFT

POWER

SWITCHES(P5)

EXT PWR 1CTS

EXT PWR 2CTS

IDGCT

GCU 2

GCU 1

IDG

REDUNDANT

CT

LOAD

SENSETO BCU(S)

IDGCT

GEN LOADS

LOAD

GROUND

28V DC

GEN LOADS

LOADMGTLOGIC

LOAD

MGTLOGIC

LOADSENSING

LOADSENSING

LOADSENSING

REDUNDANTLOADSENSETO BCU(S)



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LOAD MANAGEMENT SYSTEM

BCU 2

GROUND

U ELCU 2

U ELCU 3

GCU 4

IDGCT

GEN LOADS MGTLOGICLOADSENSING

- 243 -

747 TRAINING MANUAL


UTILITY LOAD MANAGEMENT --



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- 244 -



747 TRAINING MANUAL

9 9

DC

LEFT

P180

DC

POWER

GROUNDEX PWR 1

APU GEN 1

EXT PWR 2

LOAD

SYSTEM

GEN LOAD

ON

OFF

BCU 1

BTB GCB SSB XPC

POWER

SYSTEM

GEN LOAD BTB GCB SSB XPC

EX PWR 2

APU GEN 2

U ELCU 1

UTILITY

UTILITYU ELCU 1

U ELCU 4

ON

BUS 1

BUS 1 CONT

BUS 4

BUS 2 CONT

UTILITYSW (P5)

FROM GCU1, 2, 3, 4

LOAD

LOAD

APU PWR 2LOAD FROMBCU 2

FROM GCU1, 2, 3, 4

LOAD

LOAD

CONFIGURATION

APB POSITION

APB POSITION

CONFIGURATION

MGTLOGIC

LOADMGT

LOGIC



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UTILITY LOAD MANAGEMENT

BCU 2

GROUNDEXT PWR 1OFF

RIGHTU ELCU 4UTILITY

SW (P5)

APU PWR 1LOAD FROMBCU 1

- 247 -

747 TRAINING MANUAL

General

Autoland isolation divides the airplane electrical

system into three isolated power sources. This is done

to give the three flight control computers (FCC)

isolated power sources when they are in an autoland

approach mode.

Operation

During a triple channel autoland the three FCCs send an

isolation request to BCU 1. BCU 1 makes the decision on

how to divide the electrical system. BCU 1 uses the

position of the BTBs, GCBs, and SSB and the operation

of the TRUs to make this decision. When BCU 1 makes a

decision on how to divide the system, it sends anisolation command to BCU 2 and the GCUs to open the

related BTBs and DCIRs. When these components are in

the correct position, BCU 2 sends a signal back to the

FCCs.

ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION



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- 248 -

747 TRAINING MANUAL

9 9 9

ISOLATION

TRU

TRU

AUTOLAND

FCC (3)

BTB(S)

POSITION

POSITIONISOLATIONREQUEST

DCIR(S)

CONDITION

COMMAND

CONDITION

FCC

GCU(S) 1-4

BCU 1

DCCS 1-4

SSB

CONTROLCOMMANDS



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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION

POSITIONISOLATION CONFIRMEDBCU 2

- 249 -

9

747 TRAINING MANUAL

General

After BCU 1 gets an autoland isolation request from the

FCCs, it finds the number of generators and TRUs that

are in operation. BCU 1 then sends signals to the

related GCUs to divide the electrical system in one offive possible configurations (A, B, C, D and E).

Autoland Request

If there are four generators and four TRUs in

operation, BCU 1 tells the GCUs to go to configuration

A. This is the usual configuration for triple channel

autoland. If more than one generator channel does not

operate, BCU 1 ignores the autoland request.

NOTE: One generator and one TRU is considered an

individual generator channel (GC) by the autoland

logic. For example No. 2 generator and No. 2 TRU

make up one generator channel.

If one GC does not operate, BCU 1 sets the system to

configuration B, C, D or E.

NOTE: The SSB or any BTB opened prior to the autoland

If more than one GC stops operation during autoland,

BCU 2 removes its signal to the FCCs. If the airplane

is above 200 feet at this time, the BTBs and DCIRs go

back to their positions before autoland. If the

airplane is below 200 feet, only the DCIRs close. AC

power isolation does not change. The BTBs remain in the

last configuration until the FCCs remove the autolandisolation request.

ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION LOGIC



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NOTE: The SSB or any BTB opened prior to the autoland

isolation request will not be closed during the

autoland mode.

Autoland Operation

If a GC fails while in configuration A, BCU 1 changes

the system to configuration B, C, D or E.

- 250 -

747 TRAINING MANUAL

1 9 9 9

ABOVE

INOP

BTB(S) STAY

YES

INOP NO

YES

INOP NO

NO

YES

YES

NO

NO

NO

NO

NO

YES

YES

YES

YES

NO. 3 GEN

NO. 2 GEN

NO. 1 GEN

NO

IGNORE

RETURN ELECT

INOP

4 GEN

INOP

YES

NO

AUTOLAND REMOVE AUTO

AUTOLAND

YES

SET

SET

SET

SET

REQUESTFROM FCC

AND TRUSOPERATING

GC >1

CONFIG A

GC >0

GC >1CONFIG D

OR TRU INOP

OR TRU INOP

CONFIG C

CONFIG B

GC >1

GC >1

IN LASTPOSITION,REMAININGDCIRS CLOSE

REQUESTREMOVED

200FT

ISOLATIONCONFIRMATION

SYSTEM TOPRE-AUTOLANDCONFIG

AUTO ISOLREQUEST

OR TRU INOP

1

1

1

1

1



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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND ISOLATION LOGIC

YES

INOP NO

YES

NO. 4

IF SSB IS OPEN

SET

AND GEN IS INOP,GO TO

TRU INOP

CONFIG E GC >11

1

- 251 -

9 9

747 TRAINING MANUAL

General

There are five possible configurations that BCU 1 can

set for autoland isolation (A, B, C, D, and E). BCU 1

finds the number of generators and TRUs that are in

operation to make a decision which configuration to

use. These are the configurations and related generatoroperation:

- A all generators in operation

- B No. 1 generator not in operation

- C No. 2 generator not in operation

- D No. 3 generator not in operation

- E No. 4 generator not in operation.

The configuration for a TRU that does not operate isthe same as for a related generator that does not

operate except that the related GCB does not open.

The split system breaker must be in the closed position

for configurations B and C if the related GCB is open.

ELECT PWR -- AC ELECT LOAD DISTRIBUTION - AUTOLAND CONFIGURATIONS



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- 252 -

747 TRAINING MANUAL

/ 1 9 9 9

G1 G2 G3 G4

CONFIG A CONFIG B CONFIG C

BTB

GCB

TRU

DCIR

BTB

GCB

TRU

DCIR

SSB SSB

BTB

GCB

TRU

DCIR

SSB

BTB

GCB

TRU

SSB

BTB

GCB

TRU

SSBTRU INOP, CONFIGURES

SSB MUST BE CLOSED IN

GEN NO. 1 INOP GEN NO. 2 INOP

THE SAME AS GENERATORINOP EXCEPT THAT GCBDOES NOT TRIP.

CONFIGURATIONS B AND CIF RESPECTIVE GCB IS OPEN.IF RESPECTIVE GCB ISOPEN IN CONFIGURATION

D AND E, SSB MAYBE OPEN.

G1 G2 G3 G4 G1 G2 G3 G4

G1 G2 G3 G4 G1 G2 G3 G4



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ELECT PWR - AC ELECT LOAD DISTRIBUTION - AUTOLAND CONFIGURATIONS

CONFIG D CONFIG E

TRU

DCIR

TRU

DCIR

GEN NO. 4 INOPGEN NO. 3 INOP

- 253 -



747 TRAINING MANUAL

2 / 1 9 9 9

ENG STAT

ECS

HYD DRS GEAR

ELEC FUEL

2 3 4

OFF

ISLN

BUS 1

BUS TIE

SSB

GEN CONT

DRIVE

BUS 2 BUS 4

UTILITY

GALLEY

UTILITY

GALLEY

UTILITY

GALLEY

UTILITY

APU 1EXT 1 EXT 2APU 2

DRIVE

PRESSTEMP/

GALLEY

BUS 3

1



24-00-00

2 4 - 0 0 - 0 0 - 0 0 3

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1 0 / 2 2


ELECTRICAL POWER - SYNOPTIC PAGE

EICAS DISPLAY SELECT

CANC RCL

PANEL (P10)

- 255 -



747 TRAINING MANUAL

2 2 / 1 9 9 9

1

LOO RC TNEGP AE I C A S

D I S P L A Y

C M C M E N U

< P R E S E N T L E G F A U L T S

C ON FI DE NC E T ES T<

<

<

S

E I C A S M A I N T P A G E S

G R O U N D

H E L P >

T E S T S

/ 2

<

R E C O R D

<

<

M AN UA L S NA PS HO TS

A UT O S NA P SH OT S

1 E C S

4 E L E C

7 F L T

I C A S MM C = E I U

< 2

< 2

< 2

EC LL

1 / 3A I N T P A G E SE I C A S = E I U --

T R I C A L

C O N T

8 F U E L< 2

ELECTRICAL

28 28 28 28 28 28

35 35 35 35

APU BAT

DC-V

145

35 35

IDG OUT.TEMP

IDG RISE TEMP

115

400

115

400

115

400

115

400

AC-V

FREQ

LOAD

1APU 2 EXT 2

2 3 4

0.00 0.75 0.75

0

0

0.00

__________

10DC-A

MAIN BAT

CHG

0

0

APU 1

DIS

24

030

145 115

0

0

0.35 0.00

0

0

0.65

38

EXT 1

0.00

E LACIRTCEL



24-00-00

2 4 - 0 0 - 0 0 - 0 0 4

R e v

1

1 0 / 2


ELECTRICAL POWER - MAINTENANCE PAGE ACCESS

AUXILIARY EICAS

< A UT O S NA P SH OT S

DATE GMT 18:54:0402SEP87

- 257 -

/ 1 9 9 9

747 TRAINING MANUAL

General

The electrical power maintenance page shows electrical

system ac volts, frequency and percent load for these

power sources:

- APU generators 1 and 2

- External power 1 and 2

- IDG 1, 2, 3 and 4

DC volts and amperes show for:

- Main battery

- TRU 1, 2, 3 and 4

- APU battery

Temperature (C) shows for oil outlet and rise of each

IDG.

Voltage indications for the APU are from the C phase.

For IDG and external power voltage, the highest phase

voltage shows.

For percent load indications the phase with the highest

current shows as a percent of 250 amperes.

ELECTRICAL POWER -- MAINTENANCE PAGE



24-00-00 2

4 - 0 0 - 0 0 - 0 0 5

R e v

1

1 0 / 2 2 /


- 258 -

747 TRAINING MANUAL

/ 2 2 / 1 9 9 9

28 28 28 28 28 28

35 35 35 35

APU BAT

DC-V

145

35 35

IDG OUT.TEMP

IDG RISE TEMP

115

400

115

400

115

400

115

400

AC-V

FREQ

LOAD

1APU 2 EXT 2

2 3 4

0.00 0.75 0.75

0

0

0.00

ELECTRICAL __________

10DC-A

MAIN BAT

CHG

0

0

0.00

EXT 1 APU 1

DIS

24

030

145 115

0

0

0.35 0.00

0

0

0.65

38



24-00-00

2 4 - 0 0 - 0 0 - 0 0 5

R e v

1

1 0 /


ELECTRICAL POWER - MAINTENANCE PAGE

DATE GMT 18:54:0402SEP87

- 259 -

2 / 1 9 9 9

747 TRAINING MANUAL

General

The AGCUs sense three-phase voltage at the point of

regulation (APU generator side of APB). The BCUs

monitor C-phase from the AGCUs to get voltage and

frequency for indication.

The CT senses three-phase current. The BCUs use this

data for percent load indications. The load shows as a

percent of 250 amperes. The BCUs exchange this data

with each other on an ARINC 429 bus. The EIUs use data

from BCU 1 unless there is a malfunction with the BCU.

If this occurs, the EIUs use the data from BCU 2.

ELECTRICAL POWER -- APU INDICATION



24-00-00 2 4 - 0 0 - 0 0 - 0 0 6

R e v

1

1 0 / 2 2


- 260 -

747 TRAINING MANUAL

0 / 2 2 / 1 9 9 9

APU

FROM

VOLT

TO EIUS

AGCU

28 28 28 28 28 28

35 35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

400 400 400 400

115

400

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

0

0

0.00

ELECTRICAL

10DC-A CHG

0

0

0.00

115

400

2APU 1EXT 1

0.75

0 0 0 0

0.00 0.00 0.00 0.00 0.65

CHG

24 24 24 24

0 0 0 0

MAIN BAT

38

CT

VOLTS

TO LOAD

BCU 2FREQUENCY

APB

EIU(S)

AC-V

FREQ

LOAD 0.00

0

0 115

400

0.75

EXT 1 APU 1

GEN

REG

BCU 2



24-00-00

2 4 - 0 0 - 0 0 - 0 0 6

R e v

1

1 0


ELECTRICAL POWER - APU INDICATION

GMT18:54:0402SEP87DATE% LOAD

BCU 1NOTE: APU 1 SHOWN,

AUXILIARY EICASAPU 2 SIMILAR

- 261 -

2 2 / 1 9 9 9

747 TRAINING MANUAL

General

Voltage, frequency and percent load data for external

power 1 and 2 go to their related BCU. The BCUs

exchange this data with each other on an ARINC 429 bus.

The EIUs use data from BCU 1 unless there is a

malfunction with the BCU. If this occurs, the EIUs use

the data from BCU 2.

Voltage

The BUC senses voltage at the point of regulation

(receptacle side of XPC). The BCU senses all three

phases but only the highest phase voltage shows. This

data goes to the opposite BCU and to the EIUs.

Frequency

The BCU uses C phase to find frequency. This data goes

to the opposite BCU and to the EIUs.

Percent Load

The CT senses three-phase current and sends it directly

to the BCUs for percent load indications. The load

shows as a percent of 250 amperes. The BCU sends this

data to the opposite BCU and to the EIUs.

ELECTRICAL POWER -- EXTERNAL POWER INDICATION



24-00-00 2 4 - 0 0 - 0 0 - 0 0 7

R e v

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1 0 / 2


- 262 -

747 TRAINING MANUAL

0 / 2 2 / 1 9 9 9

28 28 28 28 28 28

35 35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

400 400 400 400

115

400

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

0

0

0.00

ELECTRICAL

10DC-A CHG

0

0

0.00

115

400

2APU 1EXT 1

0.75

0 0 0 0

0.00 0.00 0.00 0.00 0.65

CHG

24 24 24 24

0 0 0 0

MAIN BAT

38

BCU 2

AC-V

FREQ

LOAD 0.00

0

0 115

400

0.75

EXTERNAL

CT

XPC

% LOAD

VOLTS

FREQUENCY

BCU 1TO LOAD

EXTERNAL

EIU(S)

EXT 1 APU 1

POWERRECEPTACLE

POWER NO. 2



24-00-00

2 4 - 0 0 - 0 0 - 0 0 7

R e v

1

1


ELECTRICAL POWER - EXTERNAL POWER INDICATION

GMT18:54:0402SEP87DATE

NOTE: EXTERNAL POWER 1 SHOWN,

AUXILIARY EICASEXTERNAL POWER 2 SIMILAR

- 263 -

2 2 / 1 9 9 9

747 TRAINING MANUAL

General

The GCUs sense voltage, frequency and percent load data

and send it to the BCUs on an ARINC 429 bus. The BCUs

send this data to the EIUs. The EIUs use the data from

BCU 1 unless there is a malfunction with the BCU. If

this occurs, the EIUs use the data from BCU 2.

Voltage

The GCU senses voltage at the point of regulation (IDG

side of the GCB). The GCU senses all three phases, but

only the highest phase voltage shows.

Frequency

The PMG sends three-phase voltage to the GCU. The GCU

uses the A-phase to find frequency. This data then goes

to the BCUs.

Percent Load

The percent load indication is from the total current

flow in all three phases of the IDG. The CTs in the IDG

send this data to the GCU. The GCU then sends this data

to the BCUs. The load shows as a percent of 250

amperes.

ELECTRICAL POWER -- GENERATOR POWER INDICATION



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- 264 -

747 TRAINING MANUAL

1 0 / 2 2 / 1 9 9 9

28 28 28 28 28 28

35 35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

400 400 400

115

400

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

0

0

0.00

ELECTRICAL

10DC-A CHG 10

2

0

0.00 0.65

CHG

24

0

IDG

BCU 1

115 115 115

0.75

0

0.75 0.35

145 145 115

35 35 30

EIU(S)

0.00 0.00

0

0

0

0

EXT 1 APU 1

MAIN BAT

1

AC-V

FREQ

LOAD

% LOAD

FREQUENCY

TO LOAD

PMG

CT

VOLTAGE

GCU 1

400

0.75

115

0.00

0

0

0.00

0

0EXT 1 APU 1

GCB



24-00-00

2 4 - 0 0 - 0 0 - 0 0 8

R e v

1


ELECTRICAL POWER - GENERATOR POWER INDICATION

GMT18:54:0402SEP87DATEBCU 2

NOTE: IDG 1 SHOWN,

AUXILIARY EICASOTHER IDG'S SIMILAR

- 265 -

/ 2 5 / 1 9 9 9

747 TRAINING MANUAL

General

BCU 1 senses the dc volts and dc amperes for the main

battery. This data shows on the electrical power

maintenance page.

Voltage

BCU 1 senses the battery voltage at the main hot

battery bus and sends this data to the EIUs for

indication. The voltage that shows is the battery

charger voltage if the battery charger is in operation.

Current

A dc current sensor (DCCS) next to the battery on the

negative lead senses dc current from the battery. This

data goes to BCU 1 and then to the EIUs for indication.

A charge (CHG) or discharge (DIS) message shows next to

the dc current indication for charge or discharge of

the battery.

ELECTRICAL POWER -- MAIN BATTERY INDICATION



24-00-00 2 4 - 0 0 - 0 0 - 0 0 9

R e v

1

1 0


- 266 -

747 TRAINING MANUAL

1 0 / 2 5 / 1 9 9 9

28 28 28 28 28 28

35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

ELECTRICAL

10DC-A CHG

2

0

0.00

CHG

0

0

0

0

0.00 0.00 0.65

115

400

0

0

115145145

35 35 30

35

28

CHG

DC-V

DC-A

115 0 0 0 0

400 0 0 0

0.75 0.00 0.00 0.00

MAIN MAIN

DCCS

P180

VOLTAGE

CURRENT

BCU 1

BAT.

MAIN HOT

MAIN BAT

MAIN BAT

38

EXT 1 APU 1

38

EIU(S)

BAT BATCHGR

BAT BUS

VOLT



24-00-00

2 4 - 0 0 - 0 0 - 0 0 9

R e v

1


ELECTRICAL POWER - MAIN BATTERY INDICATION

GMT18:54:04

AUXILIARY EICAS

02SEP87DATE

- 267 -

0 / 2 2 / 1 9 9 9

747 TRAINING MANUAL

General

BCU 2 senses dc volts and dc amperes for the APU

battery and shows this data on the electrical power

maintenance page.

Voltage

BCU 2 senses battery voltage at the APU hot battery bus

and sends this data to the EIUs for indication. The

voltage that shows is the battery charger voltage if

the battery charger is in operation.

During an APU start (crank contactor energized) the

voltage that shows changes from APU hot battery bus

voltage to the voltage at the starter side of the crank

contactor.

Current

A dc current sensor (DCCS) next to the battery on the

negative lead senses the dc current from the battery.

This data goes to BCU 2 and then to the EIUs for

indication. During an APU start the voltage on the

starter side of the APU crank contactor inhibits the

current indications that usually show. A charge (CHG)

or discharge (DIS) message shows next to the dc current

indication for charge or discharge of the battery.

ELECTRICAL POWER -- APU BATTERY INDICATION



24-00-00 2 4 - 0 0 - 0 0 - 0 1 0

R e v

1

1 0


- 268 -

747 TRAINING MANUAL

1

1 0 / 2 2 / 1 9 9 9

BAT VOLTS

28 28 28 28 28 28

35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

ELECTRICAL

10DC-A CHG

2APU 1EXT 1

0

0

0.00 0.00

115

400

0

0

145145

35 35

35

28

10

115 0

400

0.75 0.00

BCU 2

115 115 115 115

400 400 400 400

0.75 0.75 0.75 0.00

DIS

DIS

APU BAT

EIU(S)

35

145

MAIN BAT

38

VOLTAGE

CURRENT

TO APU

R7184 APU

FROM APU

DCCS

APUAPU

APU

BATBATCHGR

(P183)

CRANKVOLTAGE

(P183)

BATTERY

CRANK

CONTACTOR(P183)

STARTERMOTOR



24-00-00

2 4 - 0 0 - 0 0 - 0 1 0

R e v

1


ELECTRICAL POWER - APU BATTERY INDICATION

GMT18:54:04

AUXILIARY EICAS

02SEP87DATE

- 269 -

1 0 / 2 5 / 1 9 9 9

747 TRAINING MANUAL

General

TRU voltage and current show on the electrical system

maintenance page.

Current

The DCCSs are in the P180 panel (one for each TRU).They sense the dc current that the TRUs supply to their

dc loads. This current data goes to the related GCU.

The GCU send the data to the BCUs. The BCUs send the

data to the EIUs. The EIUs use the data from BCU 1

unless there is a malfunction with the BCU. If this

occurs, The EIUs use the data from BCU 2.

Voltage

The related GCU senses voltage directly from the dc

bus. This voltage data goes to the BCUs. The BCUs send

the data to the EIUs. The EIUs use the data from BCU 1

unless there is a malfunction with the BCU. If this

occurs, The EIUs use the data from BCU 2.

NOTE: Voltage indication is bus voltage and does not

necessarily represent the TRU voltage for that

bus. To read individual TRU voltage the dc

isolation relay for that bus must be opened to

isolate the bus.

ELECTRICAL POWER -- TRU INDICATION



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1


- 270 -

747 TRAINING MANUAL

1

1 0 / 1 6 / 2 0 0

0

GMT18:54:04

28 28 28 28 28 28

35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

ELECTRICAL

10DC-A

2

0

0.00

CHG

0

02SEP87DATE

BCU 2

0

0.00

0

BCU 1

0

0

0.00 0.75 0.75 0.35 0.00 0.65

115

400

0

0

115115115

400 400 4000

115145145

35 35 30

TRU

DC BUS

TRU

115V

P6 TRU

28 28 28 28

35 35DC-A

DC-V

35

28

35

35

TRU

CURRENT

EIU(S)

GCU 1

38

38

EXT 1 APU 1

VOLTAGE(P180)

VOLTSCURRENT

AC

DCCS(P180)



24-00-00

2 4 - 0 0 - 0 0 - 0 1 1

R e v


ELECTRICAL POWER - TRU INDICATION

AUXILIARY EICASNOTE: TRU 1 SHOWN,OTHER TRUS SIMILAR

- 271 -



747 TRAINING MANUAL

v

1

1 0 / 2 5 / 1 9 9

9

18 54 04

28 28 28 28 28 28

35 35 35

APU BAT

DC-V

IDG OUT.TEMP

IDG RISE TEMP

AC-V

FREQ

LOAD

1APU 2 EXT 2

3 4

ELECTRICAL

10DC-A CHG 10

2

0

0.00

CHG

0

02SEP87BCU 2

0

OIL IN

OIL OUT

OIL

BCU 1

IDG GCU

OIL OUT/OIL

090286

0.75 0.75 0.35 0.00 0.65

115

400

0

0

115115115

400 400 400

75115145145

35 35 30

35EIU'S

MAIN BAT

IDG RISE TEMP

IDG OUT.TEMP 145 145 115 75

0303535

0.00

0

0

EXT 1

0

0.00

0

APU 1

TEMPPROCESSOR

RISE TEMP



24-00-00

2 4 - 0 0 - 0 0 - 0 1 2

R e v


ELECTRICAL POWER - IDG OIL TEMPERATURE INDICATION

GMT18:54:04

AUXILIARY EICAS

02SEP87DATEBCU 2 DATE 090286

- 273 -

1

1 0 / 2 2 / 1 9 9 9

747 TRAINING MANUAL

General

There is BITE circuitry in the BCUs and GCUs that can

identify an electrical power system malfunction.

Malfunctions are line relevant faults (LRF) or shop

relevant faults (SRF) (inter-wiring level). LRFs are in

CMC memory for later access. SRFs are in the related

BCU or GCU nonvolatile memory. To identify malfunctionsthe BITE system operates in these modes:

- BIT

- Ground Test

- Power up/replacement test.

BIT

There are two BIT modes. One mode is for a protectivetrip isolation (fault isolation). The other mode is the

BIT monitor which does an analysis of the electrical

system at intervals during operation.

When a protective trip occurs, the BIT identifies the

breaker/relay and the protective function that has the

possible malfunction. If the malfunction is in the GCU,

the GCU sends the LRF data to the BCU. This causes the

related EICAS message to show. The BCU also sends themalfunction data to the CMC to hold in memory.

The BIT monitor does an analysis of the electrical

monitor finds SRFs, the GCU and BCU holds them in

nonvolatile memory. If the BIT monitor finds LRFs, data

goes to the BCU. This causes the related EICAS message

to show. The BCU also sends the data to the CMC to hold

in memory. LRFs found by the BIT monitor show only

while the malfunction is active.

Ground Test

When they get a ground test request from the CMC, the

BCUs and GCUs do their ground tests. Ground tests can

start only when the GHB has power. If the ground test

finds LRFs, data goes through the BCU set by the ground

test. This data then goes to the CMC to hold in memory.

The related units hold their SRFs in non-volatile

memory.

The GCUs start the internal ground test after they get

a request from the BCUs. The two BCUs send this

request, but only one is necessary for the GCUs to

start the test.

Power Up/Replacement Test

The power up/replacement test starts automatically when

the GCUs and BCUs get power and the airplane is in theground mode. This test is the same as the ground test

except that there is no test of the non-volatile

memories of the units.

ELECTRICAL POWER -- BCU/GCU BUILT-IN TEST EQUIPMENT (BITE)



24-00-00 2 4 - 0 0 - 0 0 - 0 1 3

R e v

1


y

system at intervals during operation for malfunctions

which do not cause a protective trip. If the monitor

finds a malfunction, it automatically starts a routine

to identify the cause of the failure. If the BIT

- 274 -

747 TRAINING MANUAL

e v

1

1 0 / 2 2 / 1 9 9

9

BCU 1

GCU

GCU

GCU

GCU

P

GROUND TESTS

w

w

PAGE

DELSP

VNAV

a

w

FIX

K

L

RADNAV

MENU

HOLD

+/-0.

987

654

32

CLR/

EDCBA

O

J

N

I

M

H

L

GF

Y

T

X

SRQ

WVU

PSD

LIAF

GSM

Z

BRT

TSFO

EXECLEGS

NEXT

1

PROG

RTE ARRDEP

PAGEPREV

REFINIT

CMC

1

2

3

4



24-00-00

2 4 - 0 0 - 0 0 - 0 1 3

R e


ELECTRICAL POWER - BCU/GCU BUILT-IN TEST EQUIPMENT (BITE)

BCU 2

CDU

- 275 -

1

1 0 / 2 2 / 1 9 9 9

747 TRAINING MANUAL

General

You make ground test selections from the CMC MENU on a

CDU. You make the electrical system ground tests

selection by pushing the line select key next to 24

ELECTRICAL. The 24 ELECTRICAL selection causes the

these tests to show:

- EPGS (BCU 1)

- EPGS (BCU 2).

ELECTRICAL POWER -- GROUND TEST SELECTION



24-00-00 2 4 - 0 0 - 0 0 - 0 1 4

R e v


- 276 -

747 TRAINING MANUAL

R e v

1

1 0 / 2 2 / 1 9 9

9

/G R O U N D T E S T S

<

X X XX

E P G S B( C U )1

/G R O U N D T E S T S

<

<

X X XX

2 4 E L E C T R I C A L

2 6 F I R E P R O T E C T I O N

C M C M E N U

< P R E S E N T L E G F A U L T S

C O N F I D E N C E T E S T<

<<

S

E I C A S M A I N T P A G E SG R O U N D T E S T S

1 / 2



24-00-00

2 4 - 0 0 - 0 0 - 0 1 4

R


ELECTRICAL POWER - GROUND TEST SELECTION

< E P G S B( C U 2 )

- 277 -



e v

1

1 0 / 2 5 / 1 9 9 9

747 TRAINING MANUAL

General

This schematic shows the basic AC and DC power

distribution. Breaker control and bus protection does

not show.

ELECTRICAL POWER -- SYSTEM SCHEMATIC

ELECTRICAL POWER -- SYSTEM SCHEMATIC



24-00-00 2 4 - 0 0 - 0 0 - 0 1 6

R e


- 280 -

747 TRAINING MANUAL

6

R e v

1

0 5 / 3 1 / 2 0 0 0

1

3

3

1

2

ENERGIZED DURING APU STARTBATMAIN HOT

MAIN BAT

APU BAT

DC 4DC 3DC 2DC 1

DCIR

AC 4

AC 4AC 3AC 2

EXT 1 EXT 2

OFF

SWITCHSTANDBY POWER

BAT

AUTO

RCCB

RCCBDC VOLTAGE SINGLE TRU

OPERATION

INVERTERSTATIC

115V AC 1ñ AC STANDBY

STANDBY POWERXFER RELAY

SSB

BTB

IDG 2

TRU 2

F/O XFER

BUS VOLTAGEINSTRUMENT

SENSE UNITS

CAPT XFER

SYNCH

IDG 3

TRU 3

UTILITY

ELCU

GALLEY

ELCU

UTILITY

ELCU

GALLEY

ELCU

TRU 4

APB 2

APU 2

XPC 2

IDG 4

GCB

RCCB

RCCB

APU

RELAYSTART

APU BAT

RELAYBUS XFER

APU B/C

RELAYDISABLE

GHR

TRU1

DC GH

TRU2

DC GH

AC GHSECT 2

SECT 1AC GH

GHR GSSR GSSR

GSTR

AC GS

THERMOSWITCHMAIN BAT

RELAYDISABLEMAIN B/C

B/CMAIN APU

B/C

RCCB

RELAYSTARTAPU

THERMOSWITCHAPU BAT

GSTR

GS UTILITY

TRU 1

IDG 1

XPC 1

APU 1

APB 1

UTILITY

ELCU

ELCU

GALLEY

ELCU

UTILITY

ELCU

GALLEY

BATTERYAPU

BATAPU HOT

AC 1

XFR RLYAPU INV

APUSTATICINVERTER

1ñ

115V AC

BAT

APU STBYBUS XFR RLY

SW

APU STBYBUS XFR RLY

G H

A B

12

J

AB

J

K

BUSSYNCHBUS

D

E

F

4

F

4

K

D

E

F

G

H

RCCB

P6 APUSTBY ALTPOWER

l-PFDL-NDL-FMC



24-00-00

2 4 - 0 0 - 0 0 - 0 1 6


ELECTRICAL POWER - SYSTEM SCHEMATIC

2

3

4POWER ONENERGIZED DURING NORMAL

REMOTE CONTROL (GND=OFF)

RCCB

BATTERYMAIN T/R MODE WITH GROUND REMOVED

BAT SWSENSE RELAY

RELAYOPERATION

MAIN BATRELAY

RELAYBAT XFER

- 281 -

R e v

1

1 0 / 2 2 / 1 9 9 9

747 TRAINING MANUAL

General

This schematic shows differential protection on AC

buses. Breaker control does not show.

ELECTRICAL POWER -- BUS PROTECTION

ELECTRICAL POWER -- BUS PROTECTION



24-00-00 2 4 - 0 0 - 0 0 - 0 1 7

R


- 282 -

747 TRAINING MANUAL

7

R e v

1

0 5 / 3 1 / 2 0 0 0

4GCB

EXT2

(P715)T4019

XPC

P6P6

UTIL1

DIST

T4114(P715)

T4118(P715)

(P715)T4013

T4023(P715)

2

2APB

T4017(P615)

4BTB

(P615)

(P615)T4007

T4011

AGCU2

APU2

P415

P415

GLY 4LOADS

P6

P6

WINDOW

TRU 4

HEAT

(P714)

GSTR

UTIL

GSTRT4663

(P714)

GHR2 GHR1GSSRUTILGSSR

T4018

T4022(P714)

T4113(P714)

T4012(P714)

T4117(P714)

BCU1

APU1

AGCU1

GSB

UTIL BUSGND SERV

T4014(P514)

BTB1

T4008(P514)

GCB1

T4004(P514)

IDG1

GCU1

UTIL1 ELCU

GLY 1LOADS

ELCUGLY 1

GNDSERV

P414

T4024 P6

P7

TRU 1P6

T4016(P515)

BTB3

T4010(P515)

GCB3

IDG3

T4006(P515)

GCU3

T4021

(P92)

T4020

(P92)

(P614)T4015

2BTB

(P614)T4009

2GCB

(P614)T4005

IDG22GCU

P414

P414AC 2DIST B

AC 2DIST A

LOADSGLY 2ELCU

GLY 2

UTIL2 ELCU

HEATWINDOW

P6

P7

TRU 2

T4025

T4486(P515)

AC 3DIST

P415

LOADSGLY 3

GLY 3ELCU

3 ELCUUTIL

T4026

TRU 3

P6

P7

IDG44GCU

DIST B

DIST AAC 4

AC 4

4 ELCUUTIL

GLY 4ELCU

T4027

SSB

EXT1

XPC1

AC 1

T4018(P714)

SYNCH BUS

APB

SYNCH BUS

1

SECT 2GHB 1

SECT 1GHB 1 LOADS

BUS

UTIL2LOADS

UTIL3LOADS

UTIL4LOADS

BCU2



24-00-00

2 4 - 0 0 - 0 0 - 0 1


(P614)

P415

T4484(P514)

T4485

P85 & P183

P414AC 2DIST

5 5

(P615)T4487

NOTE: DASHED LINES SHOW CONNECTIONS

CURRENT TRANSFORMERS TO DIFFERENTIAL PROTECTION

ELECTRICAL POWER - BUS PROTECTION

BUS

- 283 -



BOEI NG 747- 400F

TRAI NI NG MANUALATA-24

ELEC POWER Version 0

Jun 1, 2002



FOR TRAINING PURPOSE ONLY PAGE 2 TECHNICAL TRAINING OFFICE

BOEI NG 747- 400F



Jun 1, 2002

ELECTRICAL POWER

General

The electrical power system consists of those systemsand components which generate, distribute and controlelectrical power to the airplane. The systems include:

- External/APU power - Engine power - DC power - Standby power

- Load distribution- Indicating

External/APU Power

External/APU power supplies electrical power duringground operations. It includes two external power

sources and two APU generators.

Engine Power

DC Power

The dc power system supplies those loads requiring dcpower. It includes the batteries and transformer rectifier units.

Standby Power

Standby power supplies power to selected loads whenthe primary source has failed.

Load Distribution

The load distribution system is used to control anddistribute ac and dc power throughout the airplane.

Indicating

Indicating includes the electrical power interfaces with

EICAS and the central maintenance computer andrelated displays.




Electrical power supplied by the engines is used for allnormal flight operations. Engine power consists of four integrated drive generators (IDG).

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ELECTRICAL POWER SYSTEM (SIMPLIFIED)

General

Electrical power is distributed in the airplane through theac and dc distribution systems. The ac distributionsystem is made up of buses:

- AC 1, 2, 3, 4- F/0 transfer (AC F/O XFR)- Capt transfer (AC CAPT XFR)

- AC standby (AC STBY)- Ground handling (AC GH)- Cargo handling (AC CH)- Ground service (AC GS)

The dc distribution system is made up of buses:

- DC 1, 2, 3, 4- DC ground handling (DC GH)- DC cargo handling (DC CH)- APU hot battery (APU HOT BAT)

M i h b (MN HOT BAT)

AC Buses 1, 2, 3, 4

The ac buses are powered by the IDGs, APU generatorsor external power carts.

An IDG is connected to its respective bus by closing theassociated generator circuit breaker (GCB). Paralleloperation of the IDGs is accomplished when theassociated bus tie breakers (BTB) and GCBs are closed.The synchronizing (synch) bus is divided into twosections by a split system breaker (SSB). With proper

use of the breakers any generator can supply power toany load bus, and any combination of the IDGs can beoperated in parallel. The power output of the APUgenerators or external power carts can also beconnected to the load buses by closing the auxiliarypower breakers (APB) or external power contactors(XPC).

Transfer Buses

There are two transfer buses; the captain's and the firstffi ' Th i ' f b i ll d




- Main hot battery (MN HOT BAT)- Main battery (MN BAT)- APU battery (APU BAT)

officer's. The captain's transfer bus is normally poweredfrom ac bus 3. If ac bus 3 is not powered, the transfer bus will transfer to ac bus 1 for power. The first officer'stransfer bus is normally powered from ac bus 2 but will

BOEI NG 747- 400F



Jun 1, 2002

transfer to ac bus 1 if ac bus 2should. lose power.

AC Standby Bus

The standby ac bus is normally powered by ac bus 3 butwill switch to the static inverter if ac bus 3 is not powered,the battery switch is on and the standby power switch isin AUTO.

The APU AC standby bus is an alternate power sourcefor the captains primary instruments when power to

those instruments fail, the battery switch is ON and thestandby power switch is in the AUTO position.

Ground Handling Bus

The ground handling bus is powered from either APUgenerator 1 or external power receptacle 1 through the

ground handling relay (GHR). The bus is poweredautomatically whenever external power or APU power isavailable. If both APU and external power are available,external power powers the bus. The ground handlingb i t d i fli ht

generator 2 or external power receptacle 2 through thecargo handling relay (CHR). The bus is poweredautomatically whenever external power or APU power isavailable.

Ground Service Bus

The ground service bus is always powered by ac bus 1 if that bus is powered. If ac bus 1 is not powered, theground service bus may be powered by external power 1or APU generator 1 through the ground service select

relay (GSSR) and ground service transfer relay (GSTR).If both external and APU power are available, externalpower will power the bus.




bus is not powered in flight.

Cargo Handling BusThe cargo handling bus is powered from either APU

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Jun 1, 2002

DC 1, 2, 3, 4

Power to dc buses 1, 2, 3, and 4 is supplied bytransformer rectifier unit (TRU). The dc buses parallelthrough the dc isolation relays (DCIR). The dc isolationrelays are controlled by the operation of the bus tieswitch (PS).

DC Ground Handling Bus

The dc ground handling bus is powered when the ac

ground handling bus is powered. The dc power issupplied by two TRUs similar to but not the same as theTRUs used on the main dc buses.

DC Cargo Handling Bus

The dc cargo handling bus is powered when the ac

cargo handling bus is powered. The dc power is suppliedby one TRU. The TRU is the same as the ones used onthe dc ground handling buses.


powered, the battery chargers power the buses andcharge the batteries.

Main and APU Battery Buses

The main and APU battery buses normally receivepower from dc bus 3. If dc bus 3 loses power, the busesreceive power from their respective batteries as long asthe battery switch is on.





The main and APU hot battery buses are powered by themain and APU batteries. when the ground service bus is

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Jun 1, 2002




BOEI NG 747- 400F



Jun 1, 2002

EXTERNAL POWER COMPONENTS

All of the components in the external power system arein the main equipment center (MEC) except the electricalsystem control panel, the generator manual reset paneland the external power panel. The external power system includes:

- External power panel with two receptacles- Ground handling relays (2)- Cargo handling relays (2)

- Current transformers (4)- External power contactors (2)- Bus control units (2)- Transformer rectifier units (3)- Ground service relays (4)- Split system breaker - Generator manual reset panel





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Jun 1, 2002

NOTES




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Jun 1, 2002

EXTERNAL POWER GENERAL OPERATION

General

Three-phase, 400 HZ, 115-volt ac power is supplied tothe airplane by two external power carts through theexternal power receptacles. Before the power isconnected to the airplane systems, two bus control units(BCU) sample it. The No. 1 BCU looks at the power coming from the aft receptacle and the No. 2 BCU looksat power coming from the forward receptacle. The BCUs

check for proper seating of the plugs, voltage, frequency,phase rotation and that the plug interlock system is notshorted to the main feeder wires. When the BCUs aresatisfied that all of these conditions are met, they turn onthe external power AVAIL lights on the electrical systemcontrol panel in the flight deck.

Ground Handling Bus

When the No. 1 BCU turns on the external power AVAILlight, it also energizes the ground handling relay (GHR)to power the ground handling bus (GHB). Cargo loading,

Cargo Handling Bus

When the No. 2 BCU turns on the external power AVAILlight, it also energizes the cargo handling relay (CHR) topower the cargo handling bus (CHB) for main deckcargo loading.

Ground Service Bus

At the forward number two left door is the ground serviceswitch. Operation of this switch signals the No. 1 BCU to

energize the ground service relays to power the groundservice bus (GSB). Interior lighting and the batterychargers are some of the systems on the GSB.

External Power

There are two momentary switches labeled EXT PWR 1

and EXT PWR 2 on the electrical system control panel.Pressing EXT PWR 1 signals BCU 1 to close itsassociated external power contactor (XPC). The ONlight in the switch comes on and the AVAIL light goes off.BCU 2 closes the split system breaker (SSB) at this time




p g g ( ) g g,cleaning outlets and fueling are some of the systems onthe GHB.

p y ( )if

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Jun 1, 2002

External Power (cont)

No other power is on the synch bus. Power is not on theairplane and is being supplied by the aft power cord.Pressing EXT

PWR 2 signals BCU 2 to trip the SSB andclose its associated XPC. The ON light in the switchcomes on and the AVAIL light goes off. Now EXT

PWR 1is powering the left side of the synchronizing (synch) bus,and EXT PWR 2 is powering the right side of the synchbus.




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Jun 1, 2002




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Jun 1, 2002

NOTES




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Jun 1, 2002

CARGO HANDLING BUS CONTROL

General

The cargo handling bus (CHB) is used for ground

operations and can only be powered on the ground.BCU No. 2 controls the application of power to the CHB.The bus is actually divided into two sections and can bepowered by either external power No. 2 or APUgenerator No. 2. Either power source may be used, butexternal power has priority if both are available.

Power cannot be applied to the aircraft busses and thecargo handling busses from the same source, due to thehigh loads anticipated on the cargo busses on thefreighter. This is accomplished by supplying a ground for the cargo handling relays through the external power contactor and the auxiliary power breaker when they are

open.

External Power

When external power is applied to the No. 2 (fwd)t l t l th BCU l th

- Frequency (375 to 425 Hz)- Phase rotation (A B C)- No faults on the interlock (pins E and F are consideredthe interlock). The faults that the BCU is looking for areovercurrent or overvoltage on pins E and F. This could

occur if he external power plug was damaged and themain ac voltage was shorted to pins E or F.- Pin E/F connected (insures that the external power plug is properly installed)

After the above conditions are satisfied, the BCU

generates the external power available signal. Externalpower will power the cargo handling busses if thefollowing is true:- CHR not failed - Internal circuits in the BCU monitor for a short to ground on the control wire to the CHRS. If ashort is sensed the BCU removes the close command tothe relay.

NOTE: A reset is accomplished by removing power onthe No. 2 external power cord.




external power receptacle, the BCU samples theaverage of all three phases for:

- Voltage (104.5 to 125 volts ac)

BOEI NG 747- 400F



Jun 1, 2002

External Power (cont)

- Electrical system not in the AIRMODE -airmodemeans that the any three IDG'S are above 6100 rpm.The BCU receives the information from air ground

logic and IDG speed inputs.

- External power contactor not closed -A ground for the CHR's is supplied through auxiliary contacts of the external power contactor when the contactor isopen.

If all of the conditions are satisfied and the inhibits arenot present, the BM energizes the two CHRS. Externalpower is then applied to the CHB.

APU Power

The auxiliary generator control unit (AGCU) samplespower being supplied by the No. 2 APU generator. Whenthe APU is above 95% and the voltage is between 104and 130 volts ac, the AGCU sends an APU power readysignal to the BCU.

- External power is not available

- The CHR's have not failed

- The electrical system is not in the air mode

- The Auxiliary control breaker is not closed




The APU will power the CHB if the following is true:

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Jun 1, 2002




BOEI NG 747- 400F



Jun 1, 2002

GROUND SERVICE BUS POWER

Power for the ground service bus (GSB) automaticallycomes from AC 1 when powered. If AC 1 is not powered,then power for the GSB is selected by pressing the

ground services switch on the panel at door 1L. Thisconnects power from either external or APU sourceswith the external source having priority. When GSBpower is from a selected source, a light in the groundservices switch on the light control panel.



BOEI NG 747- 400F



Jun 1, 2002

CARGO HANDLING TRANSFORMER RECTIFIER

One cargo handling transformer rectifier unit (TRU) is inthe forward-right MEC mounted to the station 400bulkhead.

The TRU is a solid state device that converts 115 voltsac to 28 volts dc. It maintains the dc output up to a 20ampere load. The cargo handling TRU is. powered bythe cargo handling bus.



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Jun 1, 2002

NOTES




BOEI NG 747- 400F



Jun 1, 2002

APU POWER GENERAL OPERATION

General

Three phase, 400 Hz ac power is supplied to the

airplane by two APU driven generators. Before thepower is connected to the airplane systems, twoauxiliary generator control units (AGCU) monitor thepower to insure it is at the proper voltage and frequency.When the AGCUs are satisfied that the power is good,they signal the BCUs to turn on the two APU generator

AVAIL lights on the electrical system control panel in theflight deck.

Ground Handling Bus

When the No. 1 BCU turns on the APU generator AVAILlight, it also energizes the ground handling relay (GHR)

to power the ground handling bus (GHB). Cargo loading,cleaning outlets and fueling are some of the systems onthe GHB.

Cargo Handling Bus

power the cargo handling bus (CHB) for main deckcargo loading.

Ground Service Bus

At the forward number one left door is the ground serviceswitch. Operation of this switch signals the No. 1 BCU toenergize the ground service relays to power the groundservice bus (GSB). This does not occur if ac bus No. 1 ispowered or the external power No. 1 is available.

APU Power

There are two momentary switches labeled APU GEN 1and APU GEN 2 on the electrical system control panel.Pressing APU GEN 1 signals BCU 1 to send a closesignal to AGCU 1 to close its associated auxiliary power breaker (APB). The ON light in the switch comes on and

the AVAIL light goes off.




When the No. 2 BCU turns on the APU generator AVAIL

light, it also energizes the cargo handling relay (CHR) to

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Jun 1, 2002

APU Power (cont)

BM 2 closes the SSB at this time if no other power is onthe synch bus. APU generator No. 1 is now powering theairplane. Pressing APU GEN 2 signals BM 2 to send a

close signal to AGM 2. However, BM 2 first trips the SSBand then signals AGCU 2 to close its associated APB.The ON light in the switch comes on and the AVAIL lightgoes off. APU GEN 1 is now powering the left side of thesynch bus and APU GEN 2 the right.

Pressing the APU GEN 1 switch with the APB closed,causes the BCU to send an open command to the

AGCU and APB. After receiving the open command, the AGCU also sends an open command to the APB. Either open command opens the APB.

Fault trip signals to the APB can come from either the

BCU or AGCU depending on the reason for the trip.



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Jun 1, 2002

NOTES




BOEI NG 747- 400F



Jun 1, 2002

ENGINE POWER SYSTEM (IDG)

General

The IDG portion of the engine power system involves the

mechanical aspects of the IDG and its oil coolingcomponents.

Operation

The CSD portion of the IDG is a hydromechanical device.It adds or subtracts speed from the variable input of theengine gearbox to maintain the IDG generator at 12,000rpm.

IDG oil is used for speed control, lubrication and cooling.Heat generated by the IDG is cooled by passing the oilthrough an air/oil heat exchanger and a fuel cooled oil

cooler. The cooled oil is then returned to the IDG. The oilcooler is the primary means of cooling the oil but isassisted by the air/oil heat exchanger under certainoperating conditions.

A pressure relief valve is installed in the oil return line toprevent a rupture in the oil cooler from severely

in line causes the valve to open, draining the fuel and oilmixture overboard. The valve stays open as indicated bya pop-out indicator and must be reset manually.

Control

Control and monitoring of the IDG is done by the GCU.The GCU receives oil temperature, oil pressure, and IDGspeed signals. It sends speed commands to the IDGgovernor and control signals to the air/oil heat exchanger valve.

Oil temperature comes from two temperature bulbsinside the IDG and is used for:- High oil temperature light- Oil out temperature indication- Oil rise temperature indication- Air/oil heat exchanger valve control

Oil pressure comes from an oil pressure switch insidethe IDG and is used for the IDG DRIVE light.

Speed inputs come from the magnetic pickup unit (MPU)and are used for underspeed trips and airmode inhibits.




prevent a rupture in the oil cooler from severely

damaging the IDG. The high fuel pressure in the IDG oil

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Jun 1, 2002

Control (cont)

Speed commands from the GCU to the IDG are used tocontrol IDG speed to maintain reference frequency andreal load division.

Air/oil heat exchanger valve control signals are sent tothe valve to control the opening and closing of the valve.




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Jun 1, 2002




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Jun 1, 2002

IDG COMPONENTS

The IDG system includes the:

Air/oil heat exchanger cools IDG oil. It is located at the

four o'clock position on the HPC case.

Air/oil heat exchanger valve: controlled by the GCU andlocated on the HPC case at the 4 o'clock position.

Fuel/oil cooler: cools IDG oil with fuel. It is located on theright side just below the fuel flow transmitter.

IDG - maintains the IDG generator speed at 12,000 rpm.It is on the aft, left side of the main gearbox.




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Jun 1, 2002




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Jun 1, 2002

NOTES




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Jun 1, 2002

INTEGRATED DRIVE GENERATOR

Right Side

Features of the right side of the IDG include:

- IDG housing - a two piece magnesium casting with adry weight of 117.7 lbs.

- Oil ports - the oil in and oil out ports provide aconnection point between the IDG and the externaloil cooling system. A pressure relief valve at the oil in

port protects the IDG housing fromoverpressurization in case of a core rupture of theFuel/oil cooler.

- Governor adjustment - the governor adjustment is amechanical adjustment used to set the basic speed

of the IDG.

- Drain and fill ports the oil is drained from the IDGcase by removing the case drain plug. The servicecouplings connect to the pressure fill port andoverflow drain port for IDG servicing. The overflowdrain is connected to an internal standpipe.

Case thermal relief valve - the case thermal relief valveallows hot IDG oil to drain overboard if the IDG oiltemperature exceeds 430°F/221°C.

Oil level indicator - the oil level indicator is a prismatic

sight glass. It provides a visual indication of low IDG oil.

Scavenge filter and delta pressure indicator - anon-bypassing filter on the discharge side of thescavenge pump filters all oil flow leaving the IDG. Thescavenge filter contains a pop out delta pressureindicator. A red button pops out when the pressure drop

reaches 60 psid. The differential pressure indicator islocked out below 145°F/63°C to prevent nuisancetripping.

Electrical connectors - two electrical connectors (A andB) interface with airplane wiring for control, protection

and monitoring circuits.




p p

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Jun 1, 2002

Right Side (Cont)

Case vent system aspirator - the case vent systemaspirator allows air to enter the IDG case to overcomethe vacuum created by the operation of the

charge/scavenge pumps at startup or altitudepressurization changes.

A pressure relief valve is installed in the oil return line toprevent a rupture in the oil cooler from severelydamaging the IDG. The high fuel pressure in the IDG oilin line causes the valve to open, at about 65 to 75 psig

causing a pressure indicator to pop out. The fuel and oilmixture is drained overboard. The valve stays open andmust be reset manually.

Left Side

Features of the left side of the IDG include:

- Terminal block - the main generator stator threephase output and neutral output leads areterminated at a four stud terminal block.

- Disconnect reset ring - the disconnect reset ring

connection between the IDG input and interconnectshafts.

- Muff spline - a 1.5 inches, removable male spline onthe input drive shaft provides the engine gearbox

connection. The input shaft shear section isdesigned to break with an input torque of 9000 400in-lbs.




allows ground restoration of the mechanical

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Jun 1, 2002




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Jun 1, 2002

NOTES




BOEI NG 747- 400F



Jun 1, 2002

IDG OPERATION

General

The IDG receives a mechanical input from the engine

gearbox which varies in speed. Through a network of hydromechanical components the CSD portion of theIDG drives the generator at a constant 12,000 rpm.

Mechanical Transmission

The engine gearbox drives the IDG input shaft. The input

shaft drives the planetary differential which is gearedwith the right and left pump and motor input gears. Thepump and motor output gears provide speed inputs tothe planetary differential. The combination of the inputsto the planetary differential result in a constant outputwhich drives the generator at 12,000 rpm.

Control

The IDG speed is determined by the governor. Thegovernor is a spring-biased flyweight type unit. Itreceives an oil pressure supply from the charge pumpand senses output speed of the planetary differential.

the position of the flyweights and thus the IDG speed.The coil is powered by the GCU and is used for frequency matching and real load balancing.

The governor controls the oil pressure to the control

cylinder which physically moves wobbler plates insidethe pump and motors. The position of the wobbler platesdetermine the direction and speed of the motor andpump output gears.

Oil

As oil enters from the external cooling system it passesthrough a deaerator. The deaerator removes air from theoil. The charge pump pressurizes the oil and delivers itfor lubrication, cooling and control. The nominal chargepressure is 250 psi as regulated by the charge relief valve. If the oil pressure falls below 140 psi, the charge

pressure switch closes causing the DRIVE light in theIDG disconnect switch to come on. An EICAS messageis also initiated.




The governor has a magnetic trim coil which influences

BOEI NG 747- 400F



Jun 1, 2002

Oil (cont)

Leakage from all of the hydraulic components as well aslubrication and generator cooling flow return to acommon sump by gravity. Two scavenge pumps are

used to remove oil from the sump and deliver it to theexternal cooling circuit through the scavenge filter. If thepressure differential in the external cooling circuitexceeds 250 psid, the external circuit bypass valveallows the oil to bypass the circuit.

Disconnect

In addition the IDG is equipped with a disconnect. Thethermal disconnect is integrated with the electricaldisconnect solenoid. The thermal material consists of solder in a closed chamber and is sensitive totemperatures above 199°C. Above 199°C solder melts

allowing a spring to retract the solenoid pin. Retractingthe solenoid pin allows the spring loaded disconnectplunger to engage a ramp, the clutch disconnects andthe IDG no longer operates. The thermal disconnect cannot be reset, the electrical solenoid disconnect can bereset.

Case Vent System

The case vent system consists of an aspirator mountedin the end housing and an aneroid Valve installed in theinput shaft. Air enters the IDG through the aspirator and

escapes through the aneroid valve. The constantexchange of air removes water from the IDG oil whichdecreases the formation of acid, and extends the servicelife of the oil and filters. IDG case pressure is controlledby the aneroid valve.

Case Thermal Relief

If the IDG temperature exceeds 232°C, a solder pelletwill melt allowing all oil to be drained from the IDG.




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Jun 1, 2002

IDG DISCONNECT

General

The IDG input shaft and interconnect shaft may be

disconnected at the flight deck. This allows the engine tocontinue running while shutting down a faulty IDG.

Operation

IDGs are disconnected by pressing one of the guardeddrive disconnect switches on the electrical system

control panel (P5). When the switch is pressed adisconnect solenoid in the IDG is energized allowing aspring-loaded plunger to engage threads on theinterconnect shaft. This causes the interconnect shaft tomove away from the input shaft, disconnecting the IDGfrom the input shaft. With the IDG disconnected a DRIVEDISC advisory and status message appear on EICAS.

The same disconnect signal is sent to the GM to trip theGCR and GCB. This action isolates the generator fromits electrical load.

Maintenance Practice

The disconnect switch should not be operated unless theengine is at or above idle speed. The switch may beoperated with the engine shut down, but the IDG must

be reset before the engine is started. Disconnectingbelow idle speed or with the engine shut down does notresult in a complete separation of the dog teeth.

Resetting is only on the ground following engine shutdown. This is done by pulling out on the reset ring untilthe solenoid nose pin snaps into position.

Thermal Disconnect

In addition the IDG is equipped with a ThermalDisconnect. It is integrated in the electrical disconnectsolenoid. The material consists of a solder pellet in achamber and is sensitive to greater than 199 degrees C(390 degrees F). When the IDG operating temperaturereaches this temperature the solder melts, an internallock pin sets as the disconnect pin retracts, thus the IDGclutch disconnects.




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Jun 1, 2002




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Jun 1, 2002

IDG OIL COOLER

The IDG oil cooler provides the primary cooling for theIDG during normal flight operations. It is on theright-hand side of the engine just below the fuel flow

transmitter. The heat exchanger consists of a tublar coremounted inside a welded case. Oil from the IDGcirculates continuously through the heat exchanger unless the IDG is disconnected. The oil is directed byflow control ribs across the core tubes. Metered fuel fromthe fuel flowmeter passes through core tubes absorbingIDG oil heat.




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Jun 1, 2002




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Jun 1, 2002

IDG AIR/OIL HEAT EXCHANGER AND VALVE

General

The IDG air/oil heat exchanger provides supplemental

cooling for the IDG oil. This occurs in cases of lowengine power, or high IDG oil temperature. The air for the heat exchanger is controlled by the heat exchanger valve.

Heat Exchanger

When the fuel/oil cooler has insufficient fuel flow to coolthe IDG oil or the oil outlet temperature is high, the air/oilheat exchanger will assist in cooling the IDG oil. Theair/oil heat exchanger is a tube and fin-type heatexchanger with fan air passing over the heatexchanger's fins and absorbing heat from the IDG oil.IDG oil is directed from the inlet port through tubes to anoutlet port. The heat exchanger includes a pressurerelief valve to bypass oil in the event that it becomesclogged due to contamination or high oil viscosityconditions (Open 50 ± 5 psid, close 45 psid minimum).

Valve

The IDG air/oil heat exchanger valve is a butterfly-typevalve coupled to the inlet of the IDG air/oil heatexchanger and to the fan air supply duct. It is operated

by 11th stage compressor bleed air and controlled by a28 volt dc solenoid. When the valve is signaled to open,it allows fan air to pass through the IDG air/oil heatexchanger.

On top of the valve is a position indicator arm andmanual lockout screw. The arm is attached to the valve

shaft and will point to embossed position labels on top of the valve. The lockout screw may be removed andinserted through a hole in the position indicator arm tolock the valve in the open position.




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IDG AIR/OIL HEAT EXCHANGER VALVE CONTROL

Two inputs are applied to the valve; a 28 volt dc enablingsignal and 11th stage bleed air. With 28 volts present thevalve will close by 50 psig and open by 35 psig. If the 28

volt dc signal is not present, the valve will remain open atall air pressures.

In the normal mode the generator control unit (GCU)applies 28 volts to one side of a switch in the valve.When the air pressure is less than 35 psig (low enginespeed), the switch is open keeping 28 volts from the

solenoid. With the solenoid relaxed the air is not allowedto close the valve. The valve remains open at this low air pressure and supplements the IDG oil cooling. As the air pressure increases above 50 psig, the switch closes andenergizes the solenoid which allows the air to close thevalve.

The GCU is constantly monitoring IDG oil temperature. If for any reason the oil temperature should reach 127°C,the GCU removes the 28 volts to the valve. This relaxesthe solenoid and blocks the air to the valve. The valveopens and supplements the IDG cooling.




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IDG COOLING VALVE FAILURE

General

The GCU provides 28 volts dc to close the IDG air/oil

heat exchanger valve and removes the voltage to openthe valve. The GCU monitors these valve commandsignals as well as valve position.

If the GCU senses a difference between the commandedposition and the actual. valve position a disagreementcondition will be set and sent to the BCU's. Upon

receiving the valve disagreement signal BCU 1 (BCU 2 if BCU 1 has failed) sends a valve disagreement signal tothe EIU's.

EIU Logic

The EIU receives the IDG oil temperature of all IDG's.The EIU uses these temperatures and the disagreementsignal to set the ELEC IDG X VALVE status message.This message will be set if the valve fails to open or close when directed by the GCU.

Failed to open - The IDG oil on the engine with a valve

disagreement is 20 deg C higher than an average of the

others.

Failed to close - Any IDG oil temp is more than 20 deglower than the average of the others.

NOTE: In addition to the above, the following EIU logicmust also be. satisfied prior to setting the message:

- All engines running

- All generators on line

- Valid IDG sensing

- N1 greater than 60% or less than 27%

- 600 seconds (10 min) time delay




disagreement is 20 deg C higher than an average of the

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IDG SERVICING

General

The scavenge pump recirculates heated oil through the

scavenge filter, air cooled oil cooler and fuel cooled oilcooler to the deaerator. Pressure filling will add oilthrough the cooling circuit to the IDG.

Servicing (Replenishment)

Regular servicing of the IDG does not require complete

case drain. The pressure and drain lines are attached tothe pressure and over flow drain couplings. Pressure fillthe IDG from a proper servicing cart at 5 to 15 psi. Theoil level rises above the top of the overflow drain whichestablishes the correct fill level. Continue to put oil intothe IDG until a minimum of 1 quart of oil flows into thecontainer and flow slows to a dripping condition.

NOTE: The 1 quart of oil does not include the oil thatdrained when the hose was connected to the overflowdrain coupling.

Servicing (Oil Change)

Changing the IDG oil is required for regular interval or scavenge filter damage. Procedures are similar toreplenishing the IDG. Attach the pressure and drain lines.

Remove the case drain plug and allow 1 to 1.5 gallons (4to 6 liters) to exit the case. Replace the scavenge filter as required. Pressure fill until the oil that comes out isthe same color as the oil in the service cart or 1 to 1.5gallons of oil flow from the IDG case. Install the casedrain plug and replenish the IDG with oil normally.

NOTE: After servicing, the IDG oil temperature riseshould be monitored on the EICAS electricalmaintenance page upon engine start. An abnormal risein temperature may indicate improper servicing.

WARNING:MANY WARNINGS AND CAUTIONS ARECONTAINED IN THE MAINTENANCE MANUALREGARDING IDG SERVICING. SEE SERVICINGCHAPTER 12-13-03 AND 12-22-00.




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LOAD MANAGEMENT SYSTEM

General

The load management system provides automatic

shedding and restoration of the galley and utility loads.This is done by opening and closing the associatedELCUs when an overload condition is sensed (demandexceeds capacity).

Load Shedding

During an overload condition the load managementsystem sheds the associated utility ELCUs one at a timein one-second intervals until the overload condition isremoved. The utility loads shed in the following order:

- U ELCU 1- U ELCU 4


When a generator is running isolated (BTB open) and anoverload is experienced on the remaining generators,load reduction starts with the lowest numbered U ELCU.

For example, BTB No. 2 is open and an overload occurs

on the remaining paralleled generators. The tripsequence would be:


- U ELCU 3




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Load Restoration

Load restoration occurs automatically in reverse order as load capacity is increased. The order of loadrestoration for:

- One or no generators: restore no loads.

- Two or more generators: restore all Utility loads.

Load restoration for APU and external power will occur automatically as load capacity is increased.

IDG Load Management

Generator load sensing is provided by currenttransformers (CT) in the IDGs. The current sensed bythese CTs is sent to their respective GCUs for processing. The GCUs send generator load information

to the BCUs by two separate means; an ARINC 429 busand by hard wire. The hard wire signals are redundantand are for backup in the event of a failure of the ARINC429 bus.

Inside the BCUs are normally closed relays which supply

power and grounds to the ELCUs. BCU 1 provides

power to:

- U ELCU 1 and 2 and a ground for:

- U ELCU 3 and 4 BCU 2 provides power for:

- U ELCU 3 and 4 and ground for:

- U ELCU 1 and 2

NOTE: In this way both BCUs can separately controlload shedding by either removing the power or the

ground.




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External/APU Load Management

External and APU power CTs provide currentinformation directly to the BCUs for load sheddingprotection. Whenever the external or APU load exceeds

290 amperes (on each generator or receptacle), loadshedding occurs in. the same order as with IDG loadshedding.




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NOTES




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ELECTRICAL POWER SYNOPTIC PAGE

General

Pressing the switch labeled ELEC on the EICAS display

select panel calls up the electric power synoptic page onthe auxiliary EICAS display. The synoptic page is aschematic of the electrical system. It uses a combinationof messages and color to show the condition to theelectrical system. The condition of the following isrepresented on the synoptic page:

- Electrical power flow- Integrated drive generators (IDG)- Generator circuit breakers (GCB)- Buses- Bus tie breakers (BTB)- Split system breaker (SSB)- Utility buses

Electrical Power Flow

Electrical power flow is indicated by green-colored flowsegments.

Drive

Normally the DRIVE box is white. If an IDGovertemperature or low oil pressure condition occurs,the DRIVE TEMP/PRESS message appears in the boxand the message and box turn amber.

Generator Control

When the generator is operating and the GCB is closed,the GEN CONT box is white. If the GCB opens, OFFappears in the box and the message and box turnamber.

Buses

When the main buses are powered, the bus outline andmessage are green. If the bus loses power, the busoutline and message turn amber.

Bus Tie Breakers

When the bus tie breaker is closed, the box is white. If the BTB opens, ISLN appears in the box and themessage and box turn amber.




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Utility Buses

The condition of the utility buses is indicated by usingamber to show unpowered and green to show powered.

SSB

The SSB is either displayed open (white) or closed(green).




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O A G OS O AG 60 C CA A G O C




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ELECTRICAL SYSTEM SCHEMATIC

This is an overall schematic showing basic AC and DCpower distribution. Breaker control and bus protection isnot shown.




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ELECTRICAL SYSTEM BUS PROTECTION

This is an overall schematic showing differentialprotection on AC buses. Breaker control is not shown.




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744P F ATA 24 Electrical Power

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