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Principles, Circuits, Schematics,Test Equipment, and Components

PART N 1 L

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Electrical Systems 1

Table of Contents

Introduction...................................................................................................................... 2

Electrical Principles ......................................................................................................... 4

asic !ircuits................................................................................................................... "

#che$atics...................................................................................................................... %

Testing Tools................................................................................................................. 1&

!ircuit Testing................................................................................................................ 1"

!o$ponents .................................................................................................................. 1'

Toro University Technical Training

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Electricity plays an i$portant role in $odern tur(e)uip$ent. *odern 12 +olt electrical syste$s areused al$ost e,clusi+ely in tur( e)uip$ent.

The de$ands on the electrical syste$ include-starting lighting and ignition syste$s. Electricalcircuits control the operation o( the $achines and$onitor certain $achine (unctions. They enhance theo+erall operation and also i$pro+e the operatorssa(ety through +arious sa(ety circuits. Ne/ $ethodsto control the operation and the (unction o( the$achine are $ade possible because o( electricalde+ices.

0ith the use o( $icroprocessor based controls thepotential o( electrical and electronic circuits andcontrols /ill greatly change the ease o( operationand the reliability o( current and (uture e)uip$ent.

These ne/ ad+ances in electrical syste$s /illre)uire a better understanding o( electricity andco$plete electrical syste$s to enable technicians todiagnose and repair these syste$s.


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#a(ety

#a(ety


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Electricity

Electrical #yste$ Re)uire$ents

!ircuit protection

#/itching de+ice

Po/er source

Load de+ice

!onductors

Re)uire$ents

Accessories

Electrical #yste$ /ith

E! E!* or #!*

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#eries !ircuit

Parallel !ircuit


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6 Electrical Systems

Basic Electrical Elements

Current is the directed (lo/ o( electrons through the circuit.

Voltage is the electrical pressure that causes the electrons to (lo/.

esistance is a restriction to current (lo/.


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The three electrical ele$ents ha+e a direct e((ect oneach other. The (or$ula to calculate this e((ect ish$s La/.

The illustration at the right is h$s la/. The lettersrepresent the properties in the syste$.

3 3oltage! !urrentR Resistance.

56int- re$e$ber 3!R.7

I( you kno/ any t/o o( the +alues you can apply theproper $athe$atical (or$ula and (ind the third.

Lets apply h$s La/ to a circuit

A starter $otor (or a 0R8*AN 92&& :as dra/s '&a$ps /hen the syste$ is operating correctly.#ince /e kno/ the +oltage and the current /e (indthe resistance by taking the +oltage and di+iding it bythe current. 12." +olts ; '& a$ps &.19" h$s

I( /e IN!REA#E our syste$ resistance to &.2A /hat/ill happen to our current (lo/< 12." +olts = &.2A >2." a$ps.An increase in our syste$ resistance /illdecrease the current (lo/ in our circuit. This /illresult in /hat sy$pto$ +olts. 0ith the key s/itch o((. 0iththe engine running the $eter should read 19.> +oltsor $ore 5at least 1 3 $ore than battery +oltage.7

I( /e connect our +olt$eter to the negati+e post o(the battery and to any point up to the s/itch /e /illstill $easure 12.> +olts.All /e are $easuring is the+oltage a+ailable up to the s/itch.

!onnecting the +olt$eter across the load /ith thes/itch open /ill sho/ a +oltage reading o( &.& +olts.0ithout the s/itch closed 5no current (lo/ing in thecircuit7 there is no +oltage di((erence across theload.


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16 Electrical Systems

0hen /e close the s/itch current (lo/s in thecircuit. 0e /ill then read a +oltage drop 5pressuredi((erence7 across our load. There $ust be current(lo/ing in the circuit to $easure the +oltagedi((erence across the load.

*nderstanding -oltage drop testing and .hen toperform a -oltage drop test/

0hen you encounter poor per(or$ance (ro$ anelectrical co$ponent.A test o( the circuit $ayindicate that the a$perage (lo/ is lo/er thanre)uired to operate the syste$. The area o(e,cessi+e resistance $ust be located and repaired.Per(or$ing a +oltage drop test /ill help locate thearea o( e,cessi+e resistance.

Testing for -oltage drop

!onnect the +olt$eter red lead 5F7 to the po/er 5orG$ostH positi+e7 side o( the co$ponent circuit orconnection to be tested.!onnect the +olt$eter black lead 5B7 to the ground

5or GleastH positi+e7 side o( the co$ponent circuit orconnection to be tested.#et the $eter scale to e,ceed the e,pected test+oltage. 5AutoBrange on digital +olt$eters7.Turn GonH the circuit 5re$e$ber current $ust be(lo/ing through the circuit (or resistance to be(ound7 and read the +oltage.


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3oltage ?rop Testing 5Deed #ide7

3oltage ?rop Testing

0igh mperage 2o. mperage

Circuit &3 )4 ( Circuit &5 )4 (

&.4 3olts (eed side &.2 3olts (eed side

&.4 3olts ground side &.2 3olts ground side


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1! Electrical Systems

E6ample7

8eed Side Voltage$"rop Test &engine must berunning(

Alternator output ter$inal 5F7 to battery positi+epost!an detect e,cessi+e resistance

Less than &.2 3

9round Side Voltage$"rop Test

Alternator !ase to battery negati+e post!an detect e,cessi+e resistanceLess than &.2 3

"iagnostic Tips7

Tools you need to e((ecti+ely diagnose electrical per(or$ance issues-

8no/ledge understanding

An electrical per(or$ance proble$

?3*

A$$eter 5current sensing de+ice

0hat to check-

Is current (lo/ higher or lo/er than e,pected

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