Car 66 A1 - Module 11.6 Electrical Power

8/2/2019 Car 66 A1 - Module 11.6 Electrical Power

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Module11.6: ElectricalPower

Electromagnetic Induction

ReviewOfElectricalFundamentals

D.C.Generation

D.C.Motor

VoltageRegulation

A.C.Generation

,

Batteries


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Review ofElectricallectricalFundamentals


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D.C. SERIES CIRCUIT

Inaseriescircuit,

flowsthrough

butthevoltage

istheproductof

resistance.


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PARALLEL D.C CIRCUIT

Samevoltage

resistancebut

thecurrent

througheach

is

theratioof

volta e&the

resistance.


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COMPOUND D.C CIRCUIT


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PARAMETERS OF A D.C CIRCUIT


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VARIABLE RESISTOR & POTENTIOMETER


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GENERATION OF A.C.


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GENERATION OF A.C.


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A.C FUNDAMENTALS


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LEAD & LAG IN A.C CIRCUITS


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POSIT IVE & NEGATIVE POWER

RESISTIVEINDUCTIVE

CIRCUITI UIT


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Electro MagneticI d tinduction


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Electro - Magnetism

.

EFFECTOFLAMINATION


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The transfer of electric energy from one

circuit to another without the aid of electric

connections is called induction.

When electrical energy is

transferred by means of amagne c e , s ca e

electromagnetic

.


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Electromagnetic induction occurs

whenever there is relative movement

between a conductor and a ma netic

field, provided the conductor is cutting

across e magne c nes o orce an s

not moving parallel to them.


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The relative movement may be caused by a

stationary conductor and a moving field or

field.

A moving field may be provided by a

mov ng magne or y c ang ng e va ue o

the current in an electromagnet.


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Faradays Laws Of Electromagnetic Induction

Faradays First Law - Whenever a conductorcuts magnetic flux, an e.m.f is induced in that

conductor or whenever the magnetic fluxlinked with a circuit changes an e.m.f isu .

-induced e.m.f is proportional to the rate of

-


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Direction & Magnitude of Induced EMF

The direction of induced e.m.f and current can befound by applying left-hand-rule for generators orLenzs Law.

- . .to flux-cutting i.e. dynamically induced e.m.f

enz s aw s use , w en s ue o c ange yflux-linkages i.e. statically induced e.m.f.

Faraday's second law determines the magnitudeof an induced e.m.f and Lenz's law determines the


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Classification Of Electromagnetic Induction

Generat or Ac t ion

Mov ing c onduc t or, St a t ionar y f lux

Transfo rm er ac t ion

. .

St a t ionary c onduc t or, Vary ing f lux

Sel f I nduc e d E.M.F Mutu al ly I nduc e d E.M.F


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LEFT HAND RULE FOR CONDUCTORS


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LEFT HAND RULE FOR COILS

For a current carrying

coil held in the left

hand, the encircling

fingers indicating the

,

the thumb indicates

the north pole of this

electromagnet.


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LEFT HAND RULE FOR GENERATOR

First finger Flux

t u Motion

e nger e.M.F


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RIGHT HAND RULE FOR MOTOR

First finger Flux

. .


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Fac t ors A f fec t ing Induc t ance


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Induc t anc es In Ser ies & Para l le l


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Induc t i ve React ance Vs- Frequenc y


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Transformer:- Relation Between V, I & Turns


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PRIMARY CURRENT FLOWS ONLY WHEN THE


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AUTO TRANSFORMER


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LIMITING, CHARGING &DISCHARGING OF A CAPACITOR


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SERIES R-L-C CIRCUIT


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RESONANCE IN AN A.C CIRCUIT


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D.C. Generation


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D.C. GENERATOR

DC enerator is a device

which converts mechanicalenergy n o e ec r ca energy

in the form of direct current.


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E.M.F INDUCED IN A COIL

When t hec o i l l i nk sw i t h t he

m ax . e.m .f.is induced in

.


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LEFT HAND RULE FOR GENERATOR

First finger Flux

thuMb Motion

. .

GENERATION OF D C


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GENERATION OF D.C

G A O O C


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GENERATION OF D.C

The commutator segment changes the polarity as thecoil travels through a set of poles.

EFFECT OF INCREASING NO OF COILS


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EFFECT OF INCREASING NO. OF COILS

no. of coils reducesripples of the dcvoltage.

no. o urns n eacloop will increase this

.

no. of loo s does not

increase the max. valueof generated voltage.

C


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PARTS OF A D.C GENERATOR

Armature

A cylindrical structure in

Pole Shoes

It provides the required

house the copperconductors

permanent orelectromagnet

Frame or Yoke

It provides path for the

Commutator

It converts the induced. ,

the field coils & pole pieces.. . . .

Carbon brushIts function is to collect the d.c from the commutator

ARMATURE OF A DC GENERATOR


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ARMATURE OF A DC GENERATOR

A cylindrical structure,

ma e up o ron o

provide a highly

permeable path for the

around the armature

con uctor, n w c s otsare cut to house the coils.

FIELD POLE SHOES & WINDINGS


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FIELD, POLE SHOES & WINDINGS

A practical d.c generator uses electromagnetsinstead of permanent magnets. To produce a

magne c e o e necessary s reng wpermanent magnets would greatly increase the.

FIELD FRAME OF A D C MACHINE


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FIELD FRAME OF A D.C MACHINE

COMMUTATOR & CARBON BRUSH


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COMMUTATOR & CARBON BRUSH

The brushes ride on the,

electrical contact betweenrm r il x rn l

circuit.

TYPES OF D C GENERATOR


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TYPES OF D.C GENERATOR

D.C SERIES GENERATORThe armature & field are in series, so the flux

,

e.m.f.

D C SHUNT GENERATOR


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D.C. SHUNT GENERATOR

e e w n ng s para e o arma ure,thus the flux is independent of the load

. . . .

D C COMPOUND GENERATOR


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D.C COMPOUND GENERATOR

The series field has a rising voltage with load &the shunt field has a drooping voltage chas. Soa g er oa s, ser es e compensa es e

drop & the terminal voltage is almost constant

TYPES OF D.C. GENERATOR


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TYPES OF D.C. GENERATOR

GENERATOR GENERATOR GENERATOR

ARMATURE REACTION


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ARMATURE REACTION

The current carrying armature conductor has itsown field, which increases with the current,

field.

GENERATOR WITH INTERPOLE


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GENERATOR WITH INTERPOLE

An int e rpo le

po lari t y ast he nex t m ainpole in t hed i rec t ion o fro a on usi t c oun te rac t s

reac t ion

D.C. GENERATOR CHARACTERISTICS


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Series

generator

with

chas.

Shunt

generator

withdrooping

chas.

D.C GENERATOR ASSEMBLY


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D.C GENERATOR ASSEMBLY

VOLTAGE REGULATION


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Induced e.m.f

to the flux. By

field circuit

resistance,

this e.m.f can

be controlled.

CARBON PILE VOLTAGE REGULATOR


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THREE UNIT VOLTAGE REGULATOR


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TRANSISTORISED VOLTAGE REGULATOR


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D.C MOTORS

D.C. MOTOR


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DC motor is a device which

converts

intomechanical energy

FIELD SURROUNDING


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Force ofForce of

repu s ona rac on

Current Carry ing Conduc t or


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y g

Whenever a current carrying conductor is placed in amagnetic field, a force moves this conductor from aregion of more flux to lesser flux.

TORQUE ON A CURRENT CARRYING COIL


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On the upper side of the conductor A, flux is

upwards similarly B moves downward,creating a torque.

RIGHT HAND RULE FOR MOTOR


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rs nger ux

Middle Fin er e.M.F

thuMb Motion

BASIC D.C. MOTOR OPERATION


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ere are pos ons, w en ere s no orque

on the coil. So, in a practical motor more no.of coils arranged at different angles are used.

BACK EMF IN A MOTOR


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When the rotating armature cuts the main

magnetic field, an e.m.f is induced into it,known as back emf.

Back e.m.f increases with speed.

Difference between supply voltage & back

e.m.f decides the current to the motor and

the mechanical power developed.

TYPES OF D.C. MOTOR


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SERIES, SHUNT & COMPOUND MOTORS


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SPEED CONTROL OF A DC MOTOR


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REVERSING MOTOR DIRECTION


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With SPDT switch With DPDT switch

GROWLER


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The coil &laminatedcore of

growler formt e pr mary oa transformer,

generatorsarmature

becomes thesecondary.

TESTIN G AR M ATUR E FOR SH OR TS


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The hacksaw

vibrate

there is any

armature

TESTING A GROUND IN THE ARMATURE


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If a ground exists

& the core of the

armature, the test

lam will glow. Thistest may also be

an ohmmeter.

TESTING THE FIELD COILS


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FOR SHORTED TURN FOR SHORT TO GROUN

OUTPUT OF A DC ALTERNATOR


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A.C. MOTOR


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AC motor or induction motor is a device,which converts electrical energy (in the formof a.c.) to mechanical energy.

rotating one as rotor.

ere s no e ec r ca con ac e ween estator & the rotor. Conversion of energy is

.

STATOR & ROTOR


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A rotating magnetic field is produced when thestator is excited with a 3a.c. supply. The speed ofrotat on s ca e as sync ronous spee , as

Ns=120*f /P where f is the frequency & P is the no.

SQUIRREL CAGE ROTOR


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This type of rotor consists of a cylindrical

conductors, which are heavy bars of

copper, aluminium or alloys.

The motor operation depends upon the

rotor.

CONSTRUCTION OF STATOR


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It is made of number of stampings,

windings.

Since aircraft electrical systems

operate at 400 Hz, an induction motor

6,000 rpm to 24,000 rpm.

CAPACITOR START INDUCTION MOTOR


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SLIP RING or PHASE WOUND ROTOR


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This type of rotor is provided with 3-phase windings, which are

starred internally. The other three terminals are brought out and

connected to three insulated slip rings mounted on the shaft with

brushes resting on them, under running condition, the slip rings are

s ort-c rcu te .

As soon as current flows in the stator the lines of ma netic fluxproduced in the field coils cut across the rotor and induce a voltage

in the bars. The rotor has such an extremely low resistance that the

induced voltage causes a large current to flow, and this currentcreates a magnetic field that reacts with the rotating field in the

stator.

Sl ip In An Induc t ion Mot or


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The rotor of an induction motor will assume a position

in which the induced voltage is minimised. There must

e a erence n spee e ween e ro or an e

rotating field. This difference in speed is called slip,and is ex ressed as a ercenta e of the s nchronous

speed.

% slip = Ns-N x 100NsNs :- Synchronous speed = (120 x f / P) rpmN : Motor or Rotor speed:- Motor or Rotor speed

(Ns-N) is called the slip-speed

CAPACITOR START A.C. MOTOR


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1 a.c motors are not self starting.A capacitor with starting winding offers aphase shift & starts the motor.

SHADED POLE A.C. MOTOR


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The necessary phase-splitting.

low-resistance, short-circuited

coil or copper band is placedacross one p o eac smapole. The presence of the ring

causes the magnetic fieldthrough the ringed portion ofthe pole face to lag appreciably

part of the pole-face.

SYNCHRONOUS MOTOR


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Because of the magnetic locking between the stationary & therotating parts magnetic fields, it runs at synchronous speed only.


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- .rotating magnetic field is produced. A direct current is

is produced.

,the rotor is subjected to a torque which is rapidlyreversing i.e. the rotor is subjected to torque whichtends to move it first in one direction and then in theopposite direction. Because of its large inertia, thero or can no ns an aneous y respon o suc qu c y

reversing torque and thus it remains stationary. Thus,.

.


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type of simple starter is another motor, either ac or dc, whichbrings the rotor up to approximately 90% of its synchronousspeed. The starting motor is then disconnected and the rotor

locks-in-steps with the rotating field.

Another starting method is a second winding of the squirrel-cagetype of rotor. This induction-winding brings the motor almost to

windings, the rotor pulls into step with the field. If the load on themotor is increased, rotor tends to fall back in phase but it stillcont nuous to run sync ronous y. e max mum torque, w c t e

motor can develop without pulling out of step or synchronism is,called the ull-out-tor ue.

SYNCHRONOUS MOTOR Vs- INDUCTION MOTOR

F i f h h


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For a given frequency, the synchronous motor runs at aconstant average speed whatever is the load, while thes eed of an induction motor falls somewhat with increase inload.

- .

A dc excitation is required by synchronous motor but not by

induction motor.

A s nchronous motor can be o erated over a wide ran e ofpower factor both lagging & leading but induction motoralways runs at lagging power factor, which may become

.

Generat ion Of A.C.


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Generat ion Of A.C.


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Three Phase Dis t r ibut ion

Sine a e c rrent in each of Magnetic fields add as


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Sine wave current in each ofthe coils produces sine varyingmagnetic field on the rotation

Magnetic fields add asvectors. Sum of the magneticfields produces the rotating

axis. magnetic field.

Three Phase Dis t r ibut ion

mp e cons ruc on

of 3 phase AC GeneratorOutput voltage producedby 3 phase AC Generator


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of 3-phase AC Generator by 3-phase AC Generator

STAR or

Y - Connection

3 Phase A.C Generat or


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,stationary partcontains 3 hasewindings and therotating magnetic

field induces athree phase output. .

3 Phase A.C Generat or


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A Brushless 3-Phase A.C Generator

The PMG produces an output


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The PMG produces an outputof 120V at 800 Hz which is fedto the PMG rectifier unit.

The output of the PMG rectifieris fed to the voltage regulator

which provides current for the.

The primary exciter fieldinduces current into

- .

The output of this winding isfed to three shaft-mountedThe main exciter winding is wound so as to form six

poles in order to produce an output at 115 VAC@400

a pulsating DC output which is

fed to the rotating fieldwinding.

Hz.

The excitation system is an integral part of the rotorand that there is no direct electrical connectionbetween the stator and rotor.


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Inverters,T f &ransformers &Rectifiersectifiers

3-PHASE FULL WAVE RECTIFIER


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Phase A 1, 4

Phase B 3, 6

ase 5, 2

+Ve Group 1, 3, 5 -Ve Group 2, 4, 6

Diodes between the lines of max. positive to. .



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PHASE A PHASE B PHASE C


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PHASE A PHASE B PHASE C

AVERAGE D.C.t e output conta ns pu ses n one cyc e


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Batteriesatteries

LEAD ACID BATTERY

The positive electrode is lead peroxide and the negative


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The positive electrode is lead peroxide and the negativeelectrode is spongy lead.

The electrolyte is dilute sulphuric acid.

The capacity depends on the size of the plate there arealways several plates each combined to one element by

-outside connection.

o preven any r s o ouc ng o p a es e ng s n

one another, separators are installed, a thin woodensheet and a corrugated perforated plastic-sheet.

Ni Cd BATTERY

The positive plates are made from a porous plaque on


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p p p p qwhich Nickel Hydroxide has been deposited.

The negative plates are made from similar plaques onwhich Cadmium Hydroxide is deposited.

The electrolyte used is 30% by weight of KOH

.

The specific gravity of the electrolyte remainse ween . an . .

The battery charge can not be determined by aspecific gravity check of the electrolyte.

Lead Ac i d - Vs - Ni -Cd Bat t er y

ea c attery - attery


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CELL IMBALANCE

In Ni-Cd battery the negative plate controls the cell's


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y g pvoltage characteristics. This, with slightly lowerc arge e c ency n t e pos t ve-p ates, resu ts n animbalance between the negative and positive platesin each cell.

The cell-imbalance condition is reduced by pulse

charging, when the battery is close but below fullcharge. Then, proceed to complete the charge at acons an -curren ra e o approx ma e y o e

ampere-hour capacity of the battery.

DEEP CYCLING & EQUALIZATION

Discharging the battery at a rate somewhat lowerth th t d f th it t t


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g g ythan that used for the capacity test.

When the cell voltage is down to around 0.2 volt percell, short across each cell with a shorting strap.

Leave the strap across the cells for three to eight

discharged.

.

equalization the battery is ready to charge.

NOTE

When installing the battery, connect the "hot"


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. ,

between the battery and the aircraft with yourwrenc , you w not cause a spar t e groun

lead has not been connected.

When removing a battery, always disconnect the

groun ea rst or t e same reason.

SYMBOLS


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Car 66 A1 - Module 11.6 Electrical Power

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Transcript of Car 66 A1 - Module 11.6 Electrical Power