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ElectricalElectrical

Theory I - TheTheory I - TheBasicsBasicsLet there beLet there be

light….light….

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IntroductionIntroduction• Basic TerminologyBasic Terminology• Ohm’s LawOhm’s Law•

Kirchhof’s Laws Kirchhof’s Laws !""lications!""lications• Basic #ircuit !nalysisBasic #ircuit !nalysis• Trans$ormers %ecti&ersTrans$ormers %ecti&ers

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'ow is Electricity'ow is Electricity(roduced)(roduced)

• *riction+*riction+ ,static electricity $rom rubbing,static electricity $rom rubbingwal/ing across a car"et0wal/ing across a car"et0

• (ressure+(ressure+ "ie1oelectricity $rom s2uee1ing"ie1oelectricity $rom s2uee1ingcrystals together 2uart1 watch0crystals together 2uart1 watch0

•

'eat+'eat+ 3oltage "roduced at 4unction o$3oltage "roduced at 4unction o$dissimilar metals thermocou"le0dissimilar metals thermocou"le0

• Light+Light+ 3oltage "roduced $rom light stri/ing3oltage "roduced $rom light stri/ing"hotocell solar "ower0"hotocell solar "ower0

•

#hemical+#hemical+ 3oltage "roduced $rom chemical3oltage "roduced $rom chemicalreaction wet or dry cell battery0reaction wet or dry cell battery0

• 5agnetism+5agnetism+ 3oltage "roduced using3oltage "roduced usingelectromoti3e inductionelectromoti3e induction !# or 6# generator0.!# or 6# generator0.

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Basic TerminologyBasic Terminology• #urrent I0#urrent I0

• *low o$ electric charges - electrons*low o$ electric charges - electronsor holes0 - through a conductor oror holes0 - through a conductor or

circuit "er increment o$ timecircuit "er increment o$ time• 9nit is am"ere number o$ charged9nit is am"ere number o$ charged

"articles "assing a "oint each"articles "assing a "oint eachsecond0second0

•

< am" = < coulomb>sec = ?@<A< am" = < coulomb>sec = ?@<A << electrons>secelectrons>sec

• Li/e rate o$ Cow o$ water through aLi/e rate o$ Cow o$ water through a"i"e"i"e

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Basic TerminologyBasic Terminology•

%esistance %0%esistance %0• !n electrical circuit’s o""osition to!n electrical circuit’s o""osition to

the Cow o$ current through itthe Cow o$ current through it•

5easured in ohms 5easured in ohms 00• #onductor#onductor

• !ll materials will conduct electricity8!ll materials will conduct electricity8but at 3arying resistancesbut at 3arying resistances

• ;ood conductors ha3e little;ood conductors ha3e littleresistance ie+ sil3er8 co""er8resistance ie+ sil3er8 co""er8aluminum8 iron0aluminum8 iron0

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Basic TerminologyBasic Terminology•

InsulatorInsulator• :ubstances which ofer high:ubstances which ofer high

resistance to current Cow ie+ wood8resistance to current Cow ie+ wood8

rubber8 "lastics0rubber8 "lastics0• #ircuits made o$ wires co3ered with#ircuits made o$ wires co3ered with

insulatorinsulator•

(ower (0(ower (0• %ate at which wor/ is "er$ormed%ate at which wor/ is "er$ormed• 5easured in watts D05easured in watts D0

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Ohm’s Law Ohm’s Law !""lications!""lications

•

Law+ current o$ a circuit isLaw+ current o$ a circuit isdirectly "ro"ortional to thedirectly "ro"ortional to thea""lied 3oltage and in3erselya""lied 3oltage and in3ersely

"ro"ortional to circuit resistance"ro"ortional to circuit resistance• II α 78 I78 I α <>% 7 =I%<>% 7 =I%

•

(ower(ower• ( = 7I( = 7I ( = I%0I = I ( = I%0I = I %%

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Kirchhof’s LawsKirchhof’s Laws•

Kirchhof’s #urrent Law K#L0Kirchhof’s #urrent Law K#L0• ! node is any 4unction in a circuit! node is any 4unction in a circuit

where two or more elementswhere two or more elementsmeetmeet

• #urrents into a node sum to 1ero#urrents into a node sum to 1eroO%O%

•

#urrent entering a 4unction is#urrent entering a 4unction ise2ui3alent to the current lea3inge2ui3alent to the current lea3inga 4unctiona 4unction

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Kirchhof’s LawsKirchhof’s Laws• Kirchhof’s 7oltage Law K7L0Kirchhof’s 7oltage Law K7L0

• ! loo" is any "ath in a circuit! loo" is any "ath in a circuitthat current can ta/e so that itthat current can ta/e so that itmeets bac/ u" to where it startsmeets bac/ u" to where it starts

• 7oltages around a #LO:E6 loo"7oltages around a #LO:E6 loo"sum to 1erosum to 1ero

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!""lications!""lications•

%esistors in :eries%esistors in :eries• %%TT = %= % << F %F % F %F % GG F . . .F . . .

• %esistors in (arallel%esistors in (arallel• <>%<>%TT = <>%= <>% << F <>%F <>% F <>%F <>% GG F . . .F . . .

• E@am"les+ should be able to &ndE@am"les+ should be able to &ndtotal current Cow in circuit8total current Cow in circuit8current Cow through eachcurrent Cow through eachresistor8 3oltages8 "owerresistor8 3oltages8 "owerdissi"ated8 etc.dissi"ated8 etc.

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Huestions)Huestions)

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ElectricalElectricalTheory II Theory II

TheThe!""lications!""lications'arnessing the'arnessing the(ower…(ower…

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(ower ;eneration(ower ;eneration•

#hemical #ells#hemical #ells• ElectrodesElectrodes• ElectrolyteElectrolyte• #onductor#onductor• Det>6ry BatteriesDet>6ry Batteries

•

5agnetism5agnetism

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ElectromagneticElectromagneticInductionInduction

•

*araday < G<0+*araday < G<0+• :howed that an em$ is induced in a:howed that an em$ is induced in a

conductor i$ a magnet "asses by aconductor i$ a magnet "asses by aconductorconductor

• Dhen "ole o$Dhen "ole o$magnet enteredmagnet enteredcoil8 currentcoil8 current

Cowed in oneCowed in onedirectiondirection• DhenDhendirection o$direction o$magnetmagnet

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ElectromagneticElectromagneticInductionInduction

•

5agnitude o$ induced current can5agnitude o$ induced current canbe increased by+be increased by+

• Increasing strength o$ magneticIncreasing strength o$ magnetic

&eld&eld• Increasing s"eed o$ relati3e motionIncreasing s"eed o$ relati3e motion• (ositioning o$ &eld conductor to(ositioning o$ &eld conductor to

increase number o$ magnetic linesincrease number o$ magnetic lines

o$ Cu@ cuto$ Cu@ cut• 5agnetic &eld usually "roduced5agnetic &eld usually "roduced

by electromagnetby electromagnet

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ElectromagnetElectromagnet•

:o$t iron core wound:o$t iron core woundwith coils o$ wirewith coils o$ wire• Dhen currentDhen current

"resent e@citation"resent e@citation

current08 corecurrent08 corebecomesbecomesmagneti1edmagneti1ed

• *ield strength*ield strength

determined bydetermined bynumber o$ turns andnumber o$ turns andmagnitude o$magnitude o$current+current+

BB

α JIJI

6#6#

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ElectromagneticElectromagneticInductionInduction

•

%esults in+%esults in+• ;enerator action+;enerator action+ generatorgenerator

con3erts mechanical to electricalcon3erts mechanical to electricalenergyenergy

• 5otor action+5otor action+ motor con3ertsmotor con3ertselectrical to mechanical energyelectrical to mechanical energy

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;enerator !ction;enerator !ction•

*or em$>current electricity0+*or em$>current electricity0+• 5agnetic *ield5agnetic *ield• #onductor#onductor• %elati3e 5otion b>t the two%elati3e 5otion b>t the two

•

7oltage "roduced+ ,induced em$>3oltage7oltage "roduced+ ,induced em$>3oltage

• #urrent "roduced+#urrent "roduced+,induced current ,induced current

• Le$t-handLe$t-hand rule $orrule $orgenerator actiongenerator action

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5otor !ction5otor !ction•

*or motor action*or motor actiontor2ue>motion0+tor2ue>motion0+

• 5agnetic *ield5agnetic *ield•

#onductor#onductor• #urrent Cow in conductor#urrent Cow in conductor

• Tor2ueTor2ue"roduced+"roduced+,induced,inducedtor2uetor2ue

•

%ight-hand%ight-hand

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:tandard Terminology:tandard Terminology•

:tator+:tator+ stationary housing o$ thestationary housing o$ thegenerator or motorgenerator or motor

• %otor+%otor+ rotating sha$t inside therotating sha$t inside the

statorstator• *ield windings+*ield windings+ conductors usedconductors used

to "roduce electromagnetic &eldto "roduce electromagnetic &eld•

!rmature windings+!rmature windings+ conductorsconductorsin which out"ut 3oltage isin which out"ut 3oltage is"roduced or in"ut is "ro3ided0"roduced or in"ut is "ro3ided0

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Basic TerminologyBasic Terminology• 6irect #urrent 6#06irect #urrent 6#0

• #urrent Cow is#urrent Cow isunidirectional and o$unidirectional and o$constant magnitudeconstant magnitude

battery0battery0

• !lternating #urrent !#0!lternating #urrent !#0• 5agnitude direction o$5agnitude direction o$

current Cow "eriodicallycurrent Cow "eriodically

changechange• Each se2uence called aEach se2uence called a

cyclecycle• *re2uency is cycles "er*re2uency is cycles "er

second '10second '10

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!# ;enerators!# ;enerators•

5ost electrical "ower used is !#5ost electrical "ower used is !#made by !# generatorsmade by !# generators

• Basic "rinci"le+ rotating magneticBasic "rinci"le+ rotating magnetic

&eld ,cutting through a conductor&eld ,cutting through a conductor• %egardless o$ si1e8 all !# generators%egardless o$ si1e8 all !# generatorswor/ on same "rinci"lewor/ on same "rinci"le

• Two ty"es+Two ty"es+• %e3ol3ing armature JOT used0%e3ol3ing armature JOT used0• %e3ol3ing &eld 9sed in ::T;’s8 ;T;:8%e3ol3ing &eld 9sed in ::T;’s8 ;T;:8

6;06;0

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!# ;enerators!# ;enerators•

Two ty"es+Two ty"es+• %e3ol3ing%e3ol3ing

armaturearmature

JOT used0JOT used0

• %e3ol3ing%e3ol3ing&eld 9sed in&eld 9sed in::T;’s8 ;T;:8::T;’s8 ;T;:86;06;0

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!# ;enerators!# ;enerators• *ield windings on rotor*ield windings on rotor

• 6# current "ro3ided $or &eld 3ia sli"6# current "ro3ided $or &eld 3ia sli"rings and brushes 3ice commutatorrings and brushes 3ice commutatorrings0rings0

•

%otor turned by "rime mo3er%otor turned by "rime mo3ercreates rotating magnetic &eldcreates rotating magnetic &eld• !rmature windings!rmature windings

on statoron stator• !s &eld rotates8!s &eld rotates8!# current!# current"roduced in"roduced inarmaturearmature

• :ince stationary:ince stationarycontacts8 no arc-contacts8 no arc-

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!# ;enerators!# ;enerators•

6etermining s"eed o$ !# machine+6etermining s"eed o$ !# machine+$ $ = ( %(50>< A= ( %(50>< A %(5 = < A$>( %(5 = < A$>(

• 5ust maintain constant ?A'1 out"ut5ust maintain constant ?A'1 out"ut

use s"eed go3ernor to maintainuse s"eed go3ernor to maintainconstant %(5 inde"endent o$ loading0constant %(5 inde"endent o$ loading0• 5ust also regulate 3oltage out"ut5ust also regulate 3oltage out"ut

• :ince constant %(58 must control &eld:ince constant %(58 must control &elde@citation 6# current0 to control out"ute@citation 6# current0 to control out"ut3oltage3oltage

h (hTh (h G 0 !#

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Three (hase GThree (hase G φ0 !#0 !#(ower(ower

•

(hases+ number o$ sets o$ armature(hases+ number o$ sets o$ armaturewindings on statorwindings on stator

• GGφ has three sets o$ armaturehas three sets o$ armature

windingswindings• 7oltage induced is < A7oltage induced is < A oo out o$ "hase $orout o$ "hase $oreacheach

• Out"ut+ G sinusoidal 3oltages andOut"ut+ G sinusoidal 3oltages and

currentscurrents• !llows more "ower to be deli3ered!llows more "ower to be deli3ered

with a smaller design generatorwith a smaller design generator

h (hTh (h G 0 !#

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Three (hase GThree (hase G φ0 !#0 !#(ower(ower

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!# 5otors!# 5otors•

9se !# current as in"ut to "roduce9se !# current as in"ut to "roducewor/ wor/

• 5any diferent ty"es de"ending on5any diferent ty"es de"ending on

number o$ "hases o$ !# in"ut number o$ "hases o$ !# in"ut constructionconstruction• E@+ induction motorE@+ induction motor

• In"ut !# current on stator "roducesIn"ut !# current on stator "roducesrotating &eldrotating &eld

• #urrent "roduced in conductors on rotor#urrent "roduced in conductors on rotor"roduces tor2ue"roduces tor2ue

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6# ;enerators6# ;enerators•

Basic (rinci"le+Basic (rinci"le+rotate arotate aconductor withinconductor withina magnetic &elda magnetic &eldto induce an E5*to induce an E5*

• *ield windings*ield windingslocated on statorlocated on stator

recei3e recei3ecurrent $romcurrent $romoutside sourceoutside source

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6# ;enerators6# ;enerators• !rmature windings!rmature windings

on rotoron rotor• #ommutator rings#ommutator rings

used to mechanicallyused to mechanicallyre3erse the armaturere3erse the armaturecoil connection tocoil connection tothe e@ternal circuitthe e@ternal circuit

• E5* de3elo"edE5* de3elo"edacross the brushesacross the brushesbecomes a 6#becomes a 6#3oltage>current3oltage>current

"ulsating and"ulsating andunidirectional0unidirectional0

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6# 5otors6# 5otors• Essentially the same inEssentially the same in

construction as 6#construction as 6#generatorgenerator

• Based on "rinci"le thatBased on "rinci"le thatcurrent carryingcurrent carrying

conductor "laced at aconductor "laced at aright angle to a magneticright angle to a magnetic&eld tends to mo3e in a&eld tends to mo3e in adirection "er"endicular todirection "er"endicular tomagnetic lines o$ Cu@magnetic lines o$ Cu@

• Only need to changeOnly need to changerelati3e 3oltage to gorelati3e 3oltage to gobetween generatorbetween generatormotormotor

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!# 3s 6# "ower!# 3s 6# "ower•

5any diferent 3oltages5any diferent 3oltagesre2uired on board shi"re2uired on board shi"

• Easier to trans$orm !# "owerEasier to trans$orm !# "ower$or each a""lication$or each a""lication

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Electrical 6e3icesElectrical 6e3ices•

Trans$ormerTrans$ormer• 6e3ice w>o mo3ing "arts that6e3ice w>o mo3ing "arts that

trans$ers energy $rom one circuit totrans$ers energy $rom one circuit toanother by electromagneticanother by electromagneticinductioninduction

• #onsists o$ $erromagnetic core #onsists o$ $erromagnetic core sets o$ windingssets o$ windings

•

:te"-u"+ 7:te"-u"+ 7 inin 7 7 outout• :te"-down+ 7:te"-down+ 7 inin 7 7 outout• Only wor/s with !#Only wor/s with !#

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Electrical 6e3icesElectrical 6e3ices•

%ecti&er%ecti&er• #on3erts !##on3erts !#

6#6#•

6esigned to ha3e6esigned to ha3esmall resistancesmall resistanceto current Cow into current Cow inone direction one direction large resistancelarge resistancein o""ositein o""ositedirectiondirection

• Ty"ically called aTy"ically called a

diode or recti&erdiode or recti&er

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Huestions)Huestions)