輪機(jī)英語課件lesson23

Lesson23AlternatingcurrentgeneratorsJimeiuniversityLesson23Alternatingcurrentg1Acoilofwirerotatinginamagneticfieldproducesacurrent.JimeiuniversityAcoilofwirerotatinginam2Thecurrentcanbebroughtouttotwosliprings(滑環(huán))

whichareinsulatedfromtheshaft.

JimeiuniversityThecurrentcanbebroughtout3Carbonbrushes(碳刷)restontheseringsastheyrotateandcollectthecurrentforuseinanexternalcircuit.JimeiuniversityCarbonbrushes(碳刷)restonthe4Currentcollectedinthiswaywillbealternating,thatis,changingindirectionandrisingandfallinginvalue.JimeiuniversityCurrentcollectedinthisway5Toincreasethecurrentproduced,additionalsetsofpoles(電極)

maybeintroduced.JimeiuniversityToincreasethecurrentproduc6Themagneticfieldisprovidedbyelectromagnets(電磁鐵)

soarrangedthat

adjacent(相鄰的)poleshaveoppositepolarity(極性).JimeiuniversityThemagneticfieldisprovided7These‘fieldcoils(場線圈、勵(lì)磁線圈)’,astheyarecalled,areconnectedinseriestoanexternalsourceorthemachineoutput.JimeiuniversityThese‘fieldcoils(場線圈、勵(lì)磁線圈)’,8Ifseparatecoilsorconductors(導(dǎo)線)areusedthenseveraloutputscanbeobtained.JimeiuniversityIfseparatecoilsorconductor9Threeoutputsareusuallyarrangedwithaphaseseparationof120°,toproduceathreephasesupply.JimeiuniversityThreeoutputsareusuallyarra10Thethreephasesystemismoreefficientinthatforthesamemechanicalpoweragreatertotalelectricaloutputisobtained.JimeiuniversityThethreephasesystemismore11Eachofthethreeoutputsmaybeusedinsinglephasesuppliesorinconjunctionforathreephasesupply.JimeiuniversityEachofthethreeoutputsmay12Theseparatesuppliesareconnectedineither

star

or

delta

formation.JimeiuniversityTheseparatesuppliesareconn13Thestarformationismostcommonlyusedandrequiresfourslipringsonthealternator.JimeiuniversityThestarformationismostcom14Thethreeconductorsarejoinedatacommonslipringandalsohavetheirindividualslipring.JimeiuniversityThethreeconductorsarejoine15Thecentralor

neutralline(中性線)iscommontoeachphase.JimeiuniversityThecentralorneutralline(中性16Thedeltaarrangementhastwophasesjoinedateachofthethreeslipringsonthealternator.JimeiuniversityThedeltaarrangementhastwo17Asinglephasesupplycanbetakenfromanytwosliprings.JimeiuniversityAsinglephasesupplycanbet18Sofar,alternatorconstructionhasconsideredthearmature(電樞)rotatingandthefieldcoilsstationary,JimeiuniversitySofar,alternatorconstructio19thesameelectricitygeneratingeffectisproducedifthereverseoccurs,thatis,thefieldcoilsrotateandthearmatureisstationary.Jimeiuniversitythesameelectricitygeneratin20Thisisinfactthearrangementadoptedforlarge,heavydutyalternators.JimeiuniversityThisisinfactthearrangemen21Thefieldcurrentsupplyinoldermachinescomesfromalowvoltagedirectcurrentgeneratororexciter(勵(lì)磁機(jī))onthesameshaftasthealternator.JimeiuniversityThefieldcurrentsupplyinol22Modernmachineshoweverareeither

staticallyexcited(靜態(tài)勵(lì)磁)

orofthehighspeedbrushless(無電刷型)type.JimeiuniversityModernmachineshoweverareei23Theexciterisrequiredtooperatetocounter(抵消)theeffectsofpowerfactor(功率因素)foragivenload.JimeiuniversityTheexciterisrequiredtoope24Thepowerfactorisameasureofthephasedifferencebetweenvoltageandcurrentandisexpressedasthecosine(余弦)ofthephaseangle.JimeiuniversityThepowerfactorisameasure25Withapurelyresistanceload(電阻性負(fù)載、有效負(fù)載)thevoltageareinphase(同相位),givingapowerfactorofone.JimeiuniversityWithapurelyresistanceload(26Thepowerconsumedisthereforetheproductofvoltageandcurrent.JimeiuniversityThepowerconsumedistherefor27Inductive(電感的)orcapacitive(電容的)loads,combinedwith

resistanceloads,JimeiuniversityInductive(電感的)orcapacitive(電28producelagging(滯后)orleading(超前)

powerfactorswhichhaveavaluelessthanone.Jimeiuniversityproducelagging(滯后)orleading29Thepowerconsumedistheproductofcurrent,voltageandpowerfactor.JimeiuniversityThepowerconsumedistheprod30Thealternatingcurrentgenerator

supplyingaloadhasavoltagedropresultedfromtheload.JimeiuniversityThealternatingcurrentgenera31Whentheloadhasalaggingpowerfactorthisvoltagedropisconsiderable.JimeiuniversityWhentheloadhasalaggingpo32Thereforetheexciter

inmaintainingthealternatorvoltage,mustvarywithloadcurrentandalsothepowerfactor.JimeiuniversityThereforetheexciterinmaint33Thespeedchangeoftheprimemover(原動(dòng)機(jī))mustalsobetakenintoaccount(考慮到).JimeiuniversityThespeedchangeoftheprime34Handcontrolofexcitation(勵(lì)磁)isdifficultsouseismadeofanautomaticvoltageregulator(AVR).JimeiuniversityHandcontrolofexcitation(勵(lì)磁)35TheAVRconsists

basically

ofacircuitfedfromthealternatoroutputvoltagewhich

detects

smallchangesinvoltageandJimeiuniversityTheAVRconsistsbasicallyof36andfeedsasignaltoanamplifier(放大器)whichchangestheexcitationtocorrectthevoltage.Jimeiuniversityandfeedsasignaltoanampli37Stabilizingfeaturesarealsoincorporatedinthecircuitstoavoid‘hunting(振蕩)’(constantvoltagefluctuations(波動(dòng)))orovercorrecting(過調(diào)).JimeiuniversityStabilizingfeaturesarealso38Thestaticallyexcitedalternatorhasastaticexcitationsysteminsteadofad.c.exciter.JimeiuniversityThestaticallyexcitedalterna39Thistypeofalternatorwillmoreacceptthesuddenloadingbydirecton-line(軸帶的,聯(lián)機(jī)的)startingoflargesquirrelcagemotors(鼠籠式電機(jī)).JimeiuniversityThistypeofalternatorwillm40Thestaticexcitationsystemusestransformers(變壓器)andrectifiers(整流器)toprovideseries(串激)andshunt(并激)componentsforthealternatorfield,JimeiuniversityThestaticexcitationsystemu41thatis,itiscompounded(復(fù)激勵(lì)的).Jimeiuniversitythatis,itiscompounded(復(fù)激勵(lì)的42Brushesandslipringsareusedtotransferthecurrenttothefield

coils

whicharemountedontherotor.JimeiuniversityBrushesandslipringsareused43Theterminalvoltagefromthealternatorthusgivestheno-loadvoltageandJimeiuniversityTheterminalvoltagefromthe44andtheloadcurrentprovidestheextraexcitationtogiveasteadyvoltageunderanyloadcondition.Jimeiuniversityandtheloadcurrentprovides45Thecompensation

necessaryforspeedvariationrequiresthatavoltageregulatorisalsobuiltintothesystem.JimeiuniversityThecompensationnecessaryfor46Thebrushlesshighspeedalternatorwasalsodevelopedtoeliminate(取消、消除)

d.c.exciterswiththeirassociatedcommutators(整流子)andbrushgear(電刷機(jī)構(gòu)).JimeiuniversityThebrushlesshighspeedalter47Thealternatorandexciterrotorsareonacommonshaft,whichalsocarriestherectifiers.JimeiuniversityThealternatorandexciterrot48Theexciteroutputisfedtotherectifiersandthenthroughconductorsinthehollowshafttothealternatorfieldcoils.JimeiuniversityTheexciteroutputisfedtot49Anautomaticvoltageregulatorisusedwiththistypeofalternator.JimeiuniversityAnautomaticvoltageregulator50ReadingMaterialParalleloperationofgenerators(發(fā)電機(jī)的并聯(lián)運(yùn)行)JimeiuniversityReadingMaterialParalleloper51Threephasesalternatorsarrangedforparalleloperationrequireaconsiderableamountofinstrumentations.JimeiuniversityThreephasesalternatorsarran52Thiswillincludeammeters,wattmeter,voltmeter,frequencymeterandasynchronizingdevice(同步裝置).JimeiuniversityThiswillincludeammeters,wa53Reversepowerprotection(逆功率保護(hù))isprovidedtoalternatorssincereversecurrentprotectioncannotbeused.JimeiuniversityReversepowerprotection(逆功率保護(hù)54Alternativelyvarioustrips(跳閘機(jī)構(gòu))maybeprovidedintheeventof

primemover(發(fā)動(dòng)機(jī))failuretoensurethatthealternatordoesnotactasamotor.JimeiuniversityAlternativelyvarioustrips(跳閘55Theoperationofparallelingtwoalternatorsrequiresthevoltagestobeequalandalsoinphase.JimeiuniversityTheoperationofparallelingt56Thealternatingcurrentoutputofanymachineisalwayschanging,JimeiuniversityThealternatingcurrentoutput57sofortwomachinestooperatetogether

theirvoltagesmustbechangingatthesamerate

orfrequencymustbereachingtheirmaximum(oranyothervalue)together.Jimeiuniversitysofortwomachinestooperate58Theyarethensaidtobe‘inphase’.JimeiuniversityTheyarethensaidtobe‘inp59Useisnowadaysmadeofasynchroscope(同步指示器)whenparallelingtwoa.c.machines.JimeiuniversityUseisnowadaysmadeofasync60Thesynchroscopehastwowindings(繞組)whichareconnectedonetoeachsideoftheparallelingswitch.JimeiuniversityThesynchroscopehastwowindi61Apointer(指針)isfreetorotateandismovedbythemagneticeffectofthetwowindings.JimeiuniversityApointer(指針)isfreetorotat62Whenthetwovoltagesuppliesareinphase

thepointerisstationaryinthe12o’clockposition.JimeiuniversityWhenthetwovoltagesupplies63IfthepointerisrotatingthenafrequencydifferenceexistsandJimeiuniversityIfthepointerisrotatingthe64andthedialismarkedforclockwiserotationFASTandanti-clockwiserotationSLOW,thereferencebeingtotheincomingmachinefrequency.Jimeiuniversityandthedialismarkedforclo65Toparallelanincomingmachinetoarunningmachinethereforeitisnecessarytoensurefirstlythatbothvoltagesareequal.JimeiuniversityToparallelanincomingmachin66Voltmetersareprovidedforthispurpose.Secondlythefrequenciesmustbebroughtintophase.JimeiuniversityVoltmetersareprovidedforth67InpracticethesynchroscopeusuallymovesslowlyintheFASTdirectionandparallelingswitchisclosedasthepointerreachesthe11o’clockposition.JimeiuniversityInpracticethesynchroscopeu68Thisresultsintheincomingmachineimmediatelyacceptingasmallamountofload.JimeiuniversityThisresultsintheincomingm69Asetofthreelampsmayalsobeprovidedtoenablesynchronizing.JimeiuniversityAsetofthreelampsmayalso70Thesequencemethodoflampconnectionhasakeylampconnectedacrossonephasewiththetwootherlampscrossconnectedovertheothertwophases.JimeiuniversityThesequencemethodoflampco71Ifthefrequenciesofthemachinesaredifferentthelampswillbrightenanddarkeninrotation,dependingupontheincomingfrequencybeingFASTorSLOW.JimeiuniversityIfthefrequenciesofthemach72Thecorrectmomentforsynchronizingiswhenthekeylampisdarkandtheothertwoareequallybright.JimeiuniversityThecorrectmomentforsynchro73Lesson23AlternatingcurrentgeneratorsJimeiuniversityLesson23Alternatingcurrentg74Acoilofwirerotatinginamagneticfieldproducesacurrent.JimeiuniversityAcoilofwirerotatinginam75Thecurrentcanbebroughtouttotwosliprings(滑環(huán))

whichareinsulatedfromtheshaft.

JimeiuniversityThecurrentcanbebroughtout76Carbonbrushes(碳刷)restontheseringsastheyrotateandcollectthecurrentforuseinanexternalcircuit.JimeiuniversityCarbonbrushes(碳刷)restonthe77Currentcollectedinthiswaywillbealternating,thatis,changingindirectionandrisingandfallinginvalue.JimeiuniversityCurrentcollectedinthisway78Toincreasethecurrentproduced,additionalsetsofpoles(電極)

maybeintroduced.JimeiuniversityToincreasethecurrentproduc79Themagneticfieldisprovidedbyelectromagnets(電磁鐵)

soarrangedthat

adjacent(相鄰的)poleshaveoppositepolarity(極性).JimeiuniversityThemagneticfieldisprovided80These‘fieldcoils(場線圈、勵(lì)磁線圈)’,astheyarecalled,areconnectedinseriestoanexternalsourceorthemachineoutput.JimeiuniversityThese‘fieldcoils(場線圈、勵(lì)磁線圈)’,81Ifseparatecoilsorconductors(導(dǎo)線)areusedthenseveraloutputscanbeobtained.JimeiuniversityIfseparatecoilsorconductor82Threeoutputsareusuallyarrangedwithaphaseseparationof120°,toproduceathreephasesupply.JimeiuniversityThreeoutputsareusuallyarra83Thethreephasesystemismoreefficientinthatforthesamemechanicalpoweragreatertotalelectricaloutputisobtained.JimeiuniversityThethreephasesystemismore84Eachofthethreeoutputsmaybeusedinsinglephasesuppliesorinconjunctionforathreephasesupply.JimeiuniversityEachofthethreeoutputsmay85Theseparatesuppliesareconnectedineither

star

or

delta

formation.JimeiuniversityTheseparatesuppliesareconn86Thestarformationismostcommonlyusedandrequiresfourslipringsonthealternator.JimeiuniversityThestarformationismostcom87Thethreeconductorsarejoinedatacommonslipringandalsohavetheirindividualslipring.JimeiuniversityThethreeconductorsarejoine88Thecentralor

neutralline(中性線)iscommontoeachphase.JimeiuniversityThecentralorneutralline(中性89Thedeltaarrangementhastwophasesjoinedateachofthethreeslipringsonthealternator.JimeiuniversityThedeltaarrangementhastwo90Asinglephasesupplycanbetakenfromanytwosliprings.JimeiuniversityAsinglephasesupplycanbet91Sofar,alternatorconstructionhasconsideredthearmature(電樞)rotatingandthefieldcoilsstationary,JimeiuniversitySofar,alternatorconstructio92thesameelectricitygeneratingeffectisproducedifthereverseoccurs,thatis,thefieldcoilsrotateandthearmatureisstationary.Jimeiuniversitythesameelectricitygeneratin93Thisisinfactthearrangementadoptedforlarge,heavydutyalternators.JimeiuniversityThisisinfactthearrangemen94Thefieldcurrentsupplyinoldermachinescomesfromalowvoltagedirectcurrentgeneratororexciter(勵(lì)磁機(jī))onthesameshaftasthealternator.JimeiuniversityThefieldcurrentsupplyinol95Modernmachineshoweverareeither

staticallyexcited(靜態(tài)勵(lì)磁)

orofthehighspeedbrushless(無電刷型)type.JimeiuniversityModernmachineshoweverareei96Theexciterisrequiredtooperatetocounter(抵消)theeffectsofpowerfactor(功率因素)foragivenload.JimeiuniversityTheexciterisrequiredtoope97Thepowerfactorisameasureofthephasedifferencebetweenvoltageandcurrentandisexpressedasthecosine(余弦)ofthephaseangle.JimeiuniversityThepowerfactorisameasure98Withapurelyresistanceload(電阻性負(fù)載、有效負(fù)載)thevoltageareinphase(同相位),givingapowerfactorofone.JimeiuniversityWithapurelyresistanceload(99Thepowerconsumedisthereforetheproductofvoltageandcurrent.JimeiuniversityThepowerconsumedistherefor100Inductive(電感的)orcapacitive(電容的)loads,combinedwith

resistanceloads,JimeiuniversityInductive(電感的)orcapacitive(電101producelagging(滯后)orleading(超前)

powerfactorswhichhaveavaluelessthanone.Jimeiuniversityproducelagging(滯后)orleading102Thepowerconsumedistheproductofcurrent,voltageandpowerfactor.JimeiuniversityThepowerconsumedistheprod103Thealternatingcurrentgenerator

supplyingaloadhasavoltagedropresultedfromtheload.JimeiuniversityThealternatingcurrentgenera104Whentheloadhasalaggingpowerfactorthisvoltagedropisconsiderable.JimeiuniversityWhentheloadhasalaggingpo105Thereforetheexciter

inmaintainingthealternatorvoltage,mustvarywithloadcurrentandalsothepowerfactor.JimeiuniversityThereforetheexciterinmaint106Thespeedchangeoftheprimemover(原動(dòng)機(jī))mustalsobetakenintoaccount(考慮到).JimeiuniversityThespeedchangeoftheprime107Handcontrolofexcitation(勵(lì)磁)isdifficultsouseismadeofanautomaticvoltageregulator(AVR).JimeiuniversityHandcontrolofexcitation(勵(lì)磁)108TheAVRconsists

basically

ofacircuitfedfromthealternatoroutputvoltagewhich

detects

smallchangesinvoltageandJimeiuniversityTheAVRconsistsbasicallyof109andfeedsasignaltoanamplifier(放大器)whichchangestheexcitationtocorrectthevoltage.Jimeiuniversityandfeedsasignaltoanampli110Stabilizingfeaturesarealsoincorporatedinthecircuitstoavoid‘hunting(振蕩)’(constantvoltagefluctuations(波動(dòng)))orovercorrecting(過調(diào)).JimeiuniversityStabilizingfeaturesarealso111Thestaticallyexcitedalternatorhasastaticexcitationsysteminsteadofad.c.exciter.JimeiuniversityThestaticallyexcitedalterna112Thistypeofalternatorwillmoreacceptthesuddenloadingbydirecton-line(軸帶的,聯(lián)機(jī)的)startingoflargesquirrelcagemotors(鼠籠式電機(jī)).JimeiuniversityThistypeofalternatorwillm113Thestaticexcitationsystemusestransformers(變壓器)andrectifiers(整流器)toprovideseries(串激)andshunt(并激)componentsforthealternatorfield,JimeiuniversityThestaticexcitationsystemu114thatis,itiscompounded(復(fù)激勵(lì)的).Jimeiuniversitythatis,itiscompounded(復(fù)激勵(lì)的115Brushesandslipringsareusedtotransferthecurrenttothefield

coils

whicharemountedontherotor.JimeiuniversityBrushesandslipringsareused116Theterminalvoltagefromthealternatorthusgivestheno-loadvoltageandJimeiuniversityTheterminalvoltagefromthe117andtheloadcurrentprovidestheextraexcitationtogiveasteadyvoltageunderanyloadcondition.Jimeiuniversityandtheloadcurrentprovides118Thecompensation

necessaryforspeedvariationrequiresthatavoltageregulatorisalsobuiltintothesystem.JimeiuniversityThecompensationnecessaryfor119Thebrushlesshighspeedalternatorwasalsodevelopedtoeliminate(取消、消除)

d.c.exciterswiththeirassociatedcommutators(整流子)andbrushgear(電刷機(jī)構(gòu)).JimeiuniversityThebrushlesshighspeedalter120Thealternatorandexciterrotorsareonacommonshaft,whichalsocarriestherectifiers.JimeiuniversityThealternatorandexciterrot121Theexciteroutputisfedtotherectifiersandthenthroughconductorsinthehollowshafttothealternatorfieldcoils.JimeiuniversityTheexciteroutputisfedtot122Anautomaticvoltageregulatorisusedwiththistypeofalternator.JimeiuniversityAnautomaticvoltageregulator123ReadingMaterialParalleloperationofgenerators(發(fā)電機(jī)的并聯(lián)運(yùn)行)JimeiuniversityReadingMaterialParalleloper124Threephasesalternatorsarrangedforparalleloperationrequireaconsiderableamountofinstrumentations.JimeiuniversityThreephasesalternatorsarran125Thiswillincludeammeters,wattmeter,voltmeter,frequencymeterandasynchronizingdevice(同步裝置).JimeiuniversityThiswillincludeammeters,wa126Reversepowerprotection(逆功率保護(hù))isprovidedtoalternatorssincereversecurrentprotectioncannotbeused.JimeiuniversityReversepowerprotection(逆功率保護(hù)127Alternativelyvarioustrips(跳閘機(jī)構(gòu))maybeprovidedintheeventof

primemover(發(fā)動(dòng)機(jī))failuretoensurethatthealternatordoesnotactasamotor.JimeiuniversityAlternativelyvarioustrips(跳閘128Theoperationofparallelingtwoalternatorsrequiresthevoltagestobeequalandalsoinphase.JimeiuniversityTheoperationofparallelingt129Thealternatingcurrentoutputofanymachineisalwayschanging,JimeiuniversityThealternatingcurrentoutput130sofortwomachinestooperatetogether

theirvoltagesmustbechangingatthesamerate

orfrequencymustbereachingtheirmaximum(oranyothervalue)together.Jimeiuniversitysofortwomachinestooperate131Theyarethensaidtobe‘inphase’.JimeiuniversityTheyarethensaidtobe‘inp132Useisno