Electrical Power Utilization Requirements for Electronic...

Electrical Power Utilization

Requirements for Electronic

Equipment on Military Aircraft

2012 Southern Tier Engineering Symposium &

Professional Development Seminar

Mike Elmore, Ph.D., P.E.

Mike ElmoreDirector of Engineering Design Division

Watson School of Engineering and Applied Science

Binghamton University

Experience

Lockheed Martin, Owego, NY (Systems Engineer)

EandM Power, Binghamton, NY (Consulting Engineer)

BAE Systems, Johnson City, NY (Systems Engineer)

IBM, Endicott, NY/Celestica Corp., Johnson City, NY (Hardware

Design Engineer & Manager)

General Electric, Johnson City, NY (Hardware Design Engineer)

Education

Ph.D., Electrical Engineering, Binghamton University

M.S.E.E., Electrical Engineering, Syracuse University

B.S.E.E., Electrical Engineering, University of Vermont

M. Ed., Secondary Math Education, University of Vermont

B.A., Philosophy, University of Vermont

Other

Professional Engineer (P.E.) NY State License and Registration

Senior Member of IEEE

Member of PELS, ASEE, SAE, & Tau Beta Pi

10/16/2012 2012 SOUTHERN TIER ENGINEERING SYMPOSIUM &

PROFESSIONAL DEVELOPMENT SEMINAR

2

Have done detailed power electronics

design for both military and commercial

products.

Was Electrical Power Working Group

lead and electrical power airworthiness

signatory on the VH-71 presidential

helicopter project.

Outline

Definitions

Military Aircraft Electrical Power Requirements

MIL-STD-704

Mid-term Quiz

Military Aircraft Electrical Power Test Procedures

MIL-HDBK-704

Other Aircraft Electrical Power Requirements in Brief

Final Exam



3

Military Aircraft Electrical Power Requirements

MIL-STD-704 (6 October 1959)

MIL-STD-704A (9 August 1966)

MIL-STD-704B (17 November 1975)

MIL-STD-704C (30 December 1977)

MIL-STD-704D (30 September 1980)

MIL-STD-704E (1 May 1991)

MIL-STD-704F (12 March 2004)



4

Definitions - Basic

3.29 Utilization equipment.

Utilization equipment is that equipment which receives power from the electric power system.

3.4 Aircraft electric power systems.

An aircraft electric power system consists of a main power source, emergency power sources, power conversion equipment, control and protection devices, and an interconnection network (wires, cables, connectors, etc.). The main power is derived from aircraft generators driven by the aircraft propulsion engines. Emergency power is derived from batteries, engine bleed air, independent auxiliary power units, ram air driven generators, or hydraulically driven generators.



5

Definitions (1 of 6) Ref. 1

Aircraft Electrical Power Generation

System Example – Simplified Boeing 767



6

Ref. 2

Main Gen Main Gen

Aux Gen

AC-to-DC AC-to-DC

Battery

AC Bus Tie Breakers

DC Bus Tie Breaker

Ref. 3

KC-46 tanker

Definitions – Normal Operation

3.18 Normal operation. (Electrical System)

Normal operation occurs when the system is operating as intended in the absence of any fault or malfunction that degrades performance beyond established requirements.

It includes all system functions required for aircraft operation except during the electric starting of propulsion engines and the battery start of an auxiliary power unit.

Normal operation includes switching of utilization equipment, prime mover speed changes, synchronizing and paralleling of power sources, and operation from external power sources.

4.2.2.1 Normal operation. (Utilization equipment)

Utilization equipment shall provide the level of performance specified in its detail specification.



7

Ref. 1Definitions (2 of 6)

Definitions – Abnormal Operation

3.2 Abnormal operation. (Electrical System)

Abnormal operation occurs when a malfunction or failure in the electric system has taken place and the protective devices of the system are operation to remove the malfunction or failure from the remainder of the system before the limits for abnormal operation are exceeded. The power source may operate in a degraded mode on a continuous basis where the power characteristics supplied to the utilization equipment exceed normal operation limits but remain within the limits for abnormal operation.

4.2.2.2 Abnormal operation. (Utilization equipment)

Utilization equipment shall be permitted a degradation or loss of function unless otherwise specified in its detail specification. Utilization equipment shall not suffer damage or cause an unsafe condition. Utilization equipment shall automatically resume full performance when normal operation of the electrical system is restored.



8


Definitions – Emergency Operation

3.13 Emergency operation. (Electrical System)

Emergency operation occurs following the loss of the main generating equipment when a limited electric source, independent of the main system, is used to power a reduced complement of distribution and utilization equipment selected to maintain flight and personnel safety.

3.2.2.4 Emergency operation. (Utilization equipment)

Utilization equipment shall provide the level of performance specified in its detail specification when such performance is essential for flight or safety.



9


Definitions – Starting Operation

3.12 Starting operation. (Electrical System)

Electric starting operation is a specialized case of normal electric system operating conditions where the normal voltage limits may be exceeded due to the high electric demand. The voltage limits for normal operation may be exceeded during the following starting conditions:

a. An electric start of the propulsion engine. (Battery power, aircraft DC power or external power applied on the aircraft bus.)

b. A battery start of an auxiliary power unit.

4.2.2.5 Starting operation. (Utilization equipment)

Utilization equipment shall provide the level of performance specified in its detail specification when performance is essential during the starting operation.



10


Definitions – Transfer Operation

3.27 Transfer operation. (Electrical System)

Transfer operation occurs when the electric system transfers between power sources, including transfers from or to external power sources.

4.2.2.3 Transfer operation. (Utilization equipment)

Utilization equipment may not be required to operate under the transfer condition unless a level of performance is specified by its detail specification. Utilization equipment shall automatically resume specified performance when normal operating characteristics are resumed.



11


Summary of Modes

1. Normal

2. Abnormal

3. Emergency

4. Starting

5. Transfer



12

FIGURE 1. Load

unbalance limits for

three-phase

utilization

equipment.



13

Ref. 1

FIGURE 2. Phasor

diagram showing

required phase

sequence

relationship.



14

Ref. 1

FIGURE 3. Envelope

of normal 400 Hz and

variable frequency

AC voltage transient.



15

Ref. 1

FIGURE 4. Limits for 400 Hz and variable frequency AC

overvoltage or undervoltage.



16

Ref. 1

FIGURE 5. Envelope

of normal 400 Hz AC

frequency transient.



17

Ref. 1

FIGURE 6. Limits for

400 Hz AC

overfrequency or

underfrequency.



18

Ref. 1

Does utilization equipment

have to work in this region?

FIGURE 7. Maximum distortion spectrum of 400 Hz and

variable frequency AC voltage.



19

Ref. 1

FIGURE 8. Envelope

of normal 60 Hz

voltage transient.



20

Ref. 1

FIGURE 9. Limits for 60 Hz AC overvoltage and undervoltage.



21

Ref. 1

FIGURE 10.

Envelope of normal

60 Hz AC frequency

transient.



22

Ref. 1

FIGURE 11. Limits

for 60 Hz AC

overfrequency and

underfrequency.



23

Ref. 1

FIGURE 12. Maximum distortion spectrum of 60 Hz AC voltage.



24

Ref. 1

FIGURE 13.

Envelope of normal

voltage transients

for 28 volts DC

system.



25

Ref. 1

FIGURE 14. Limits for overvoltage and undervoltage

for 28 volts DC system.



26

Ref. 1

FIGURE 15. Maximum distortion spectrum for 28 volts DC system.



27

Ref. 1

FIGURE 16.

Envelope of normal

voltage transient for

270 volts DC system.



28

Ref. 1

FIGURE 17. Limits for DC overvoltage and undervoltage

for 270 volts DC system.



29

Ref. 1

FIGURE 18. Maximum distortion spectrum for 270 volts DC system.



30

Ref. 1

Other

5.1 Transfer operation characteristics. Under conditions of bus or power source transfers, voltage and frequency shall not vary between zero and normal operating limits for longer than 50 milliseconds. A normal transient may occur upon completion of a transfer.

5.3.2.4 Electric starting. The DC voltage in electric starting operation shall be between 12 and 29 volts. Electric starting of an auxiliary power unit (other than battery starts) is a normal operating function and is not included under this condition.



31

Midterm Quiz1. What is the current revision of MIL-STD-704?

ANS: F

2. What are the 5 operating modes of a military aircraft electrical system?

ANS: Normal, Abnormal, Emergency, Transfer, & Starting

3. (T / F) - Electrical utilization equipment is allowed to suffer damage during abnormal electrical system operation.

ANS: False

4. (T / F) - During emergency AC electrical system operation all power characteristics are the same as during normal AC operation.

ANS: True

5. (T / F) - During normal DC electrical system operation the DC voltage is always a steady-state 22.0 to 29.0 Volts.

ANS: False



32

Military Aircraft Electrical Power Test Procedures

MIL-HDBK-704-1 – Overview

MIL-HDBK-704-2 – Single Phase, 400Hz, 115 Volt

MIL-HDBK-704-3 – Three Phase, 400Hz, 115 Volt

MIL-HDBK-704-4 – Single Phase, Variable Frequency, 115 Volt

MIL-HDBK-704-5 – Three Phase, Variable Frequency, 115 Volt

MIL-HDBK-704-6 – Single Phase, 60 Hz, 115 Volt

MIL-HDBK-704-7 – 270 VDC

MIL-HDBK-704-8 – 28 VDC

All published 9 April 2004



33

28 VDC

Remember: MIL-STD-704 published 14 MAR 2004

MIL-HDBK-704-8 Test Methods

METHOD LDC101 Load Measurements

METHOD LDC102 Steady State Limits for Voltage

METHOD LDC103 Voltage Distortion Spectrum

METHOD LDC104 Total Ripple

METHOD LDC105 Normal Voltage Transients

METHOD LDC201 Power Interrupt


METHOD LDC302 Abnormal Voltage Transients


METHOD LDC501 Starting Voltage Transients

METHOD LDC601 Power Failure

METHOD LDC602 Phase Reversal



34

Normal

Abnormal

Emergency

Typical Test Set-up for MIL-HDBK-704 Methods



35

FIGURE LDC101-1.

Normal operation -

load and current

distortion

measurement.

Ref. 4

METHOD LDC101

Load Measurements



36

Method 1 of 12

Ref. 4

TABLE LDC101-I.

MIL-STD-704 limits for load,

inrush current, current distortion factor,

and current spectrum

for 28 volt DC utilization equipment.

TABLE LDC101-II.

Sample data sheet

for LDC101 load

measurements.

Ref. 4

METHOD LDC102

Steady State (Normal) Limits for Voltage



37

Method 2 of 12

TABLE LDC102-II.

Test conditions for steady state

limits of DC voltage.

TABLE LDC102-III.

Sample data sheet for LDC102 steady state limits for voltage.

Ref. 4

Ref. 4

Probably

an Error

METHOD LDC103

Voltage Distortion Spectrum.



38

Ref. 1

Ref. 4

Method 3 of 12

TABLE LDC103-II.

Test conditions for voltage distortion spectrum.

METHOD LDC104

Total Ripple



39

Method 4 of 12

TABLE LDC104-I.

MIL-STD-704 limits

for ripple DC voltage distortion.

TABLE LDC104-II.

Ripple frequency and amplitude.

Ref. 4

Ref. 4

METHOD LDC105

Normal Voltage Transients



40

Over

Under

Ref. 1Ref. 4

Method 5 of 12

TABLE LDC105-III.

Test conditions for MIL-STD-704B,

C, D, E and F

normal voltage transients.

METHOD LDC201

Power Interrupt



41

Ref. 4

Method 6 of 12

TABLE LDC201-II.

Test conditions

for transfer interrupt.

Note: Transient

METHOD LDC301

Steady State (Abnormal) Limits for Voltage



42

Method 7 of 12

TABLE LDC301-III. Sample data sheet for LDC301

abnormal steady state limits for voltage.

TABLE LDC301-II.

Test conditions for abnormal steady

state limits of DC voltage.

TABLE LDC301-I. MIL-STD-704 abnormal limits for steady state voltage.

Note: No

frequency

parameter here.

Ref. 4

Ref. 4

Ref. 4

Probably

Another Error

METHOD LDC302

Abnormal Voltage Transients



43

Over

Ref. 1

Ref. 4

Method 8 of 12

METHOD LDC302




44

Under

Ref. 1

Ref. 4

Method 8 of 12

METHOD LDC302




45

Ref. 4

Method 8 of 12

Combined

METHOD LDC401

Steady State (Emergency) Limits for Voltage



46

Method 9 of 12

TABLE LDC401-III. Sample data sheet for LDC401

emergency steady state limits for voltage and frequency.

TABLE LDC401-II.

Test conditions for emergency steady

state limits of DC voltage.

TABLE LDC401-I. MIL-STD-704 emergency limits for steady state voltage.

Note: No

Frequency

parameter

here,

but they put it

here.

Ref. 4

Ref. 4

Ref. 4

METHOD LDC501

Starting Voltage Transients



47

TABLE LDC501-III. Test conditions for

MIL-STD-704D, E and F starting voltage transients.

Method 10 of 12

TABLE LDC501-IV. Sample data sheet for LDC501

starting voltage transients for MIL-STD-704A, B, C, D, E & F.

MIL-STD-704A,

B, and C are much

less severe.

Ref. 4

Ref. 4

METHOD LDC601

Power Failure



48

Method 11 of 12

TABLE LDC601-II.

Test conditions for power failures.

TABLE LDC601-III.

Sample data sheet

for LDC601 power failure.

Power Failure Region

So, what is the difference with the undervoltage

region of METHOD LDC302? ANS: Duration

Ref. 4

Ref. 4

Ref. 1

METHOD LDC602

Phase Reversal



49

Method 12 of 12

TABLE LDC602-I. MIL-STD-704 phase reversal requirement.

TABLE LDC602-II.

Sample data sheet

for LDC602 phase reversal.

Ref. 4

Ref. 4

Comparing MIL-STD-704 Editions



50

28 VDC MIL-STD-704 Edition

A B D E F Comments on Editions B, D, E, and F

Normal Voltage Steady State

(NLSS)24 VDC 22 VDC 22 VDC 22 VDC 22 VDC No differences

Normal Voltage Steady State

(NHSS)28.5 VDC 29 VDC 29 VDC 29 VDC 29 VDC No differences

Voltage Distortion SpectrumFigure 7

MIL-STD-704A

Figure 6

MIL-STD-704B

Figure 9

MIL-STD-704D

Figure 8

MIL-STD-704E

Figure 15

MIL-STD-704F

No differences between E and F.

No differences between B and D to 20kHz.

E&F differ from B&D in the mid- to high

frequency range.

Voltage Ripple

2 Volts Peak

to Mean

Figure 7

MIL-STD-704A

1.5 Volts Peak

to Average

Figure 6

MIL-STD-704B

1.5 Volts Peak

to Average

Figure 9

MIL-STD-704D

1.5 Volts Peak

to Average

Figure 8

MIL-STD-704E

1.5 Volts Peak

to Average

Figure 15

MIL-STD-704F

No differences between E and F.

No differences between B and D to 20kHz.

E&F differ from B&D in the mid- to high

frequency range.

Normal Voltage Transients

Figure 9

MIL-STD-704A

Locus of

equivalent Step

Function Curves

2 and 3

Figure 7

MIL-STD-704B

Figure 10 MIL-

STD-704D

Figure 9 MIL-

STD-704E

Figure 13

MIL-STD-704FNo differences

Comparing MIL-STD-704 Editions



51

28 VDC MIL-STD-704 Edition

A B D E F Comments on Editions B, D, E, and F

Power Interrupt 50 msec. 50 msec. 50 msec. 50 msec. 50 msec. No differences

Abnormal Voltage Steady State

(ALSS)22.5 VDC 20.0 VDC 20.0 VDC 20.0 VDC 20.0 VDC No differences

Abnormal Voltage Steady State

(AHSS)30.0 VDC 31.5 VDC 31.5 VDC 31.5 VDC 31.5 VDC No differences


Figure 9

MIL-STD-704A

Locus of equivalent

Step Function

Curves 1 and 4

Figure 8

MIL-STD-

704B

Figure 12

MIL-STD-

704D

Figure 11

MIL-STD-

704E

Figure 14

MIL-STD-704F

Comment 3 - Editions E and F are the same,

but differ from B and D (not significantly)

B and D drop from 50V at 45 msec.,

whereas E and F drop from 50V at 50 msec.

B returns from 0 V in 5 sec., whereas D, E, and F return in 7 sec.

The 0 voltage limit is unclear for all of these specifications.

5.2.3 in Edition B suggests that 0 V can continue indefinitely.

Emergency Voltage Steady

State (ELSS)16.0 VDC 18.0 VDC 16.0 VDC 16.0 VDC 16.0 VDC Comment 4 - Editions D, E, and F are 16V, whereas B is 18V.

Emergency Voltage Steady

State (EHSS)24.0 VDC 29.0 VDC 29.0 VDC 29.0 VDC 29.0 VDC No differences

Starting Voltage Transients16.0 VDC to 28.5

VDC

Use 704C

Limits

12.0 VDC to

29.0 VDC

12.0 VDC to

29.0 VDC

12.0 VDC to 29.0

VDC

Comment 5 - Edition B does not specify starting voltage limits.

MIL-HDBK-704-8 says to use the edition C limits,

which are the same as the Emergency limits (16.0V to 30.0V).

Power Failure

7 sec.

Figure 9

Curve 4

MIL-STD-704A

5 sec.

Figure 8

MIL-STD-

704B

7 sec.

Figure 12

MIL-STD-

704D

7 sec.

Figure 11

MIL-STD-

704E

7 sec.

Figure 14

MIL-STD-704F

Comment 6 - Editions D, E, and F are 7-sec. at the lower limit,

whereas edition B is 5-sec.

Phase Reversal N/A N/A N/A N/A

Phase reversal

does not

cause damage

Comment 7 - Editions B, D, and E are the same,

but differ from F (significantly)

Other Aircraft Electrical Power Requirements

RTCA/DO-160F (2007) Environmental Conditions and Test Procedures for Airborne Equipment

Section 16 – Power Input

Section 17 – Voltage Spikes

Section 18 – Audio Frequency Conduction Susceptibility –Power Inputs

This is one commercial standard in the United States.

Some utilization equipment will comply with earlier versions of this standard (A – E).



52

In Summary

MIL-STD-704 has been discussed

Editions A, B, C, D, E, and F

AC (60Hz, 400Hz, Variable Frequency, Single and Three (3) Phase) Specifications

MIL-HDBK-704 has been discussed

Eight (8) sections: Overview, 400Hz - 1ᶲ and 3ᶲ, Variable Hz -1ᶲ and 3ᶲ, 60Hz - 1ᶲ all 115VAC, 280VDC, and 28VDC.

RTCA/DO160E has been briefly mentioned

How it all comes together has been briefly discussed



53

Final Exam (1 of 2)

1. What is the current US commercial aircraft electrical power standard?

ANS: RTCA/DO-160F

2. (T / F) - MIL-STD-704F requires that utilization equipment be tested to the appropriate MIL-HDBK-704 procedure.

ANS: True (but ambiguous)

3. Of the six (6) MIL-STD-704 standards which one is most unlike the others in terms of power quality?

ANS: A

4. How long is a power transfer, as specified in MIL-STD-704?

ANS: 50ms

5. What is the commercial electrical power standard in the US?

ANS: RTCA/DO-160



54

Final Exam (2 of 2)

6. What three (3) AC electrical power frequencies are specified in MIL-STD-704F?

ANS: 60Hz, 400Hz, and variable frequency

7. (T / F) – All test methods require that voltage measurements be made within 10cm of the power supply.

ANS: False

8. (T / F) – All editions of MIL-STD-704 require a phase reversal test.

ANS: False

9. (T / F) – Different electrical utilization equipment designed to meet different editions of MIL-STD-704 can be installed on the same aircraft.

ANS: True or False

10. What organization within the government is responsible for MIL-STD-704?

ANS: NAVAIR



55

Electrical Power Utilization

Requirements for Electronic

Equipment on Military Aircraft

2012 Southern Tier Engineering Symposium &

Professional Development Seminar

Mike Elmore, Ph.D., P.E.

References

1. Department of Defense Interface Standard, Aircraft Electric Power Characteristics, MIL-STD-704F, 12 March 2004.

2. Moir, Ian and Seabridge, Allan, Aircraft Systems: Mechanical, electrical, and avionics subsystems integration, 2nd Edition, Professional Engineering Publishing, 2001, p. 147.

3. http://www.boeing.com/defense-space/military/ kc46a/index.html

4. Department of Defense Handbook: Guidance for Test Procedures for Demonstration of Utilization Equipment Compliance to Aircraft Electrical Power Characteristics: 28VDC: (Part 8 of 8 Parts), MIL-HDBK-704-8, 9 April 2004.



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Finally - Required or not?

4.4 Test requirements. …The applicable test methods of MIL-HDBK-704 shall be used to determine that the utilization equipment complies with this standard….

6.10.1 Compatibility and testing. …To ensure utilization equipment is compatible with the aircraft power, systems testing as outlined in MIL-HDBK-704-1 through -8 should be performed….

This language only appears in MIL-STD-704.



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