轮机英语课件lesson23

Lesson23AlternatingcurrentgeneratorsJimeiuniversityLesson23Alternatingcurrentg1Acoilofwirerotatinginamagneticfieldproducesacurrent.JimeiuniversityAcoilofwirerotatinginam2Thecurrentcanbebroughtouttotwosliprings(滑环)

whichareinsulatedfromtheshaft.

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

maybeintroduced.JimeiuniversityToincreasethecurrentproduc6Themagneticfieldisprovidedbyelectromagnets(电磁铁)

soarrangedthat

adjacent(相邻的)poleshaveoppositepolarity(极性).JimeiuniversityThemagneticfieldisprovided7These‘fieldcoils(场线圈、励磁线圈)’,astheyarecalled,areconnectedinseriestoanexternalsourceorthemachineoutput.JimeiuniversityThese‘fieldcoils(场线圈、励磁线圈)’,8Ifseparatecoilsorconductors(导线)areusedthenseveraloutputscanbeobtained.JimeiuniversityIfseparatecoilsorconductor9Threeoutputsareusuallyarrangedwithaphaseseparationof120°,toproduceathreephasesupply.JimeiuniversityThreeoutputsareusuallyarra10Thethreephasesystemismoreefficientinthatforthesamemechanicalpoweragreatertotalelectricaloutputisobtained.JimeiuniversityThethreephasesystemismore11Eachofthethreeoutputsmaybeusedinsinglephasesuppliesorinconjunctionforathreephasesupply.JimeiuniversityEachofthethreeoutputsmay12Theseparatesuppliesareconnectedineither

star

or

delta

formation.JimeiuniversityTheseparatesuppliesareconn13Thestarformationismostcommonlyusedandrequiresfourslipringsonthealternator.JimeiuniversityThestarformationismostcom14Thethreeconductorsarejoinedatacommonslipringandalsohavetheirindividualslipring.JimeiuniversityThethreeconductorsarejoine15Thecentralor

neutralline(中性线)iscommontoeachphase.JimeiuniversityThecentralorneutralline(中性16Thedeltaarrangementhastwophasesjoinedateachofthethreeslipringsonthealternator.JimeiuniversityThedeltaarrangementhastwo17Asinglephasesupplycanbetakenfromanytwosliprings.JimeiuniversityAsinglephasesupplycanbet18Sofar,alternatorconstructionhasconsideredthearmature(电枢)rotatingandthefieldcoilsstationary,JimeiuniversitySofar,alternatorconstructio19thesameelectricitygeneratingeffectisproducedifthereverseoccurs,thatis,thefieldcoilsrotateandthearmatureisstationary.Jimeiuniversitythesameelectricitygeneratin20Thisisinfactthearrangementadoptedforlarge,heavydutyalternators.JimeiuniversityThisisinfactthearrangemen21Thefieldcurrentsupplyinoldermachinescomesfromalowvoltagedirectcurrentgeneratororexciter(励磁机)onthesameshaftasthealternator.JimeiuniversityThefieldcurrentsupplyinol22Modernmachineshoweverareeither

staticallyexcited(静态励磁)

orofthehighspeedbrushless(无电刷型)type.JimeiuniversityModernmachineshoweverareei23Theexciterisrequiredtooperatetocounter(抵消)theeffectsofpowerfactor(功率因素)foragivenload.JimeiuniversityTheexciterisrequiredtoope24Thepowerfactorisameasureofthephasedifferencebetweenvoltageandcurrentandisexpressedasthecosine(余弦)ofthephaseangle.JimeiuniversityThepowerfactorisameasure25Withapurelyresistanceload(电阻性负载、有效负载)thevoltageareinphase(同相位),givingapowerfactorofone.JimeiuniversityWithapurelyresistanceload(26Thepowerconsumedisthereforetheproductofvoltageandcurrent.JimeiuniversityThepowerconsumedistherefor27Inductive(电感的)orcapacitive(电容的)loads,combinedwith

resistanceloads,JimeiuniversityInductive(电感的)orcapacitive(电28producelagging(滞后)orleading(超前)

powerfactorswhichhaveavaluelessthanone.Jimeiuniversityproducelagging(滞后)orleading29Thepowerconsumedistheproductofcurrent,voltageandpowerfactor.JimeiuniversityThepowerconsumedistheprod30Thealternatingcurrentgenerator

supplyingaloadhasavoltagedropresultedfromtheload.JimeiuniversityThealternatingcurrentgenera31Whentheloadhasalaggingpowerfactorthisvoltagedropisconsiderable.JimeiuniversityWhentheloadhasalaggingpo32Thereforetheexciter

inmaintainingthealternatorvoltage,mustvarywithloadcurrentandalsothepowerfactor.JimeiuniversityThereforetheexciterinmaint33Thespeedchangeoftheprimemover(原动机)mustalsobetakenintoaccount(考虑到).JimeiuniversityThespeedchangeoftheprime34Handcontrolofexcitation(励磁)isdifficultsouseismadeofanautomaticvoltageregulator(AVR).JimeiuniversityHandcontrolofexcitation(励磁)35TheAVRconsists

basically

ofacircuitfedfromthealternatoroutputvoltagewhich

detects

smallchangesinvoltageandJimeiuniversityTheAVRconsistsbasicallyof36andfeedsasignaltoanamplifier(放大器)whichchangestheexcitationtocorrectthevoltage.Jimeiuniversityandfeedsasignaltoanampli37Stabilizingfeaturesarealsoincorporatedinthecircuitstoavoid‘hunting(振荡)’(constantvoltagefluctuations(波动))orovercorrecting(过调).JimeiuniversityStabilizingfeaturesarealso38Thestaticallyexcitedalternatorhasastaticexcitationsysteminsteadofad.c.exciter.JimeiuniversityThestaticallyexcitedalterna39Thistypeofalternatorwillmoreacceptthesuddenloadingbydirecton-line(轴带的,联机的)startingoflargesquirrelcagemotors(鼠笼式电机).JimeiuniversityThistypeofalternatorwillm40Thestaticexcitationsystemusestransformers(变压器)andrectifiers(整流器)toprovideseries(串激)andshunt(并激)componentsforthealternatorfield,JimeiuniversityThestaticexcitationsystemu41thatis,itiscompounded(复激励的).Jimeiuniversitythatis,itiscompounded(复激励的42Brushesandslipringsareusedtotransferthecurrenttothefield

coils

whicharemountedontherotor.JimeiuniversityBrushesandslipringsareused43Theterminalvoltagefromthealternatorthusgivestheno-loadvoltageandJimeiuniversityTheterminalvoltagefromthe44andtheloadcurrentprovidestheextraexcitationtogiveasteadyvoltageunderanyloadcondition.Jimeiuniversityandtheloadcurrentprovides45Thecompensation

necessaryforspeedvariationrequiresthatavoltageregulatorisalsobuiltintothesystem.JimeiuniversityThecompensationnecessaryfor46Thebrushlesshighspeedalternatorwasalsodevelopedtoeliminate(取消、消除)

d.c.exciterswiththeirassociatedcommutators(整流子)andbrushgear(电刷机构).JimeiuniversityThebrushlesshighspeedalter47Thealternatorandexciterrotorsareonacommonshaft,whichalsocarriestherectifiers.JimeiuniversityThealternatorandexciterrot48Theexciteroutputisfedtotherectifiersandthenthroughconductorsinthehollowshafttothealternatorfieldcoils.JimeiuniversityTheexciteroutputisfedtot49Anautomaticvoltageregulatorisusedwiththistypeofalternator.JimeiuniversityAnautomaticvoltageregulator50ReadingMaterialParalleloperationofgenerators(发电机的并联运行)JimeiuniversityReadingMaterialParalleloper51Threephasesalternatorsarrangedforparalleloperationrequireaconsiderableamountofinstrumentations.JimeiuniversityThreephasesalternatorsarran52Thiswillincludeammeters,wattmeter,voltmeter,frequencymeterandasynchronizingdevice(同步装置).JimeiuniversityThiswillincludeammeters,wa53Reversepowerprotection(逆功率保护)isprovidedtoalternatorssincereversecurrentprotectioncannotbeused.JimeiuniversityReversepowerprotection(逆功率保护54Alternativelyvarioustrips(跳闸机构)maybeprovidedintheeventof

primemover(发动机)failuretoensurethatthealternatordoesnotactasamotor.JimeiuniversityAlternativelyvarioustrips(跳闸55Theoperationofparallelingtwoalternatorsrequiresthevoltagestobeequalandalsoinphase.JimeiuniversityTheoperationofparallelingt56Thealternatingcurrentoutputofanymachineisalwayschanging,JimeiuniversityThealternatingcurrentoutput57sofortwomachinestooperatetogether

theirvoltagesmustbechangingatthesamerate

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

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

whichareinsulatedfromtheshaft.

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

maybeintroduced.JimeiuniversityToincreasethecurrentproduc79Themagneticfieldisprovidedbyelectromagnets(电磁铁)

soarrangedthat

adjacent(相邻的)poleshaveoppositepolarity(极性).JimeiuniversityThemagneticfieldisprovided80These‘fieldcoils(场线圈、励磁线圈)’,astheyarecalled,areconnectedinseriestoanexternalsourceorthemachineoutput.JimeiuniversityThese‘fieldcoils(场线圈、励磁线圈)’,81Ifseparatecoilsorconductors(导线)areusedthenseveraloutputscanbeobtained.JimeiuniversityIfseparatecoilsorconductor82Threeoutputsareusuallyarrangedwithaphaseseparationof120°,toproduceathreephasesupply.JimeiuniversityThreeoutputsareusuallyarra83Thethreephasesystemismoreefficientinthatforthesamemechanicalpoweragreatertotalelectricaloutputisobtained.JimeiuniversityThethreephasesystemismore84Eachofthethreeoutputsmaybeusedinsinglephasesuppliesorinconjunctionforathreephasesupply.JimeiuniversityEachofthethreeoutputsmay85Theseparatesuppliesareconnectedineither

star

or

delta

formation.JimeiuniversityTheseparatesuppliesareconn86Thestarformationismostcommonlyusedandrequiresfourslipringsonthealternator.JimeiuniversityThestarformationismostcom87Thethreeconductorsarejoinedatacommonslipringandalsohavetheirindividualslipring.JimeiuniversityThethreeconductorsarejoine88Thecentralor

neutralline(中性线)iscommontoeachphase.JimeiuniversityThecentralorneutralline(中性89Thedeltaarrangementhastwophasesjoinedateachofthethreeslipringsonthealternator.JimeiuniversityThedeltaarrangementhastwo90Asinglephasesupplycanbetakenfromanytwosliprings.JimeiuniversityAsinglephasesupplycanbet91Sofar,alternatorconstructionhasconsideredthearmature(电枢)rotatingandthefieldcoilsstationary,JimeiuniversitySofar,alternatorconstructio92thesameelectricitygeneratingeffectisproducedifthereverseoccurs,thatis,thefieldcoilsrotateandthearmatureisstationary.Jimeiuniversitythesameelectricitygeneratin93Thisisinfactthearrangementadoptedforlarge,heavydutyalternators.JimeiuniversityThisisinfactthearrangemen94Thefieldcurrentsupplyinoldermachinescomesfromalowvoltagedirectcurrentgeneratororexciter(励磁机)onthesameshaftasthealternator.JimeiuniversityThefieldcurrentsupplyinol95Modernmachineshoweverareeither

staticallyexcited(静态励磁)

orofthehighspeedbrushless(无电刷型)type.JimeiuniversityModernmachineshoweverareei96Theexciterisrequiredtooperatetocounter(抵消)theeffectsofpowerfactor(功率因素)foragivenload.JimeiuniversityTheexciterisrequiredtoope97Thepowerfactorisameasureofthephasedifferencebetweenvoltageandcurrentandisexpressedasthecosine(余弦)ofthephaseangle.JimeiuniversityThepowerfactorisameasure98Withapurelyresistanceload(电阻性负载、有效负载)thevoltageareinphase(同相位),givingapowerfactorofone.JimeiuniversityWithapurelyresistanceload(99Thepowerconsumedisthereforetheproductofvoltageandcurrent.JimeiuniversityThepowerconsumedistherefor100Inductive(电感的)orcapacitive(电容的)loads,combinedwith

resistanceloads,JimeiuniversityInductive(电感的)orcapacitive(电101producelagging(滞后)orleading(超前)

powerfactorswhichhaveavaluelessthanone.Jimeiuniversityproducelagging(滞后)orleading102Thepowerconsumedistheproductofcurrent,voltageandpowerfactor.JimeiuniversityThepowerconsumedistheprod103Thealternatingcurrentgenerator

supplyingaloadhasavoltagedropresultedfromtheload.JimeiuniversityThealternatingcurrentgenera104Whentheloadhasalaggingpowerfactorthisvoltagedropisconsiderable.JimeiuniversityWhentheloadhasalaggingpo105Thereforetheexciter

inmaintainingthealternatorvoltage,mustvarywithloadcurrentandalsothepowerfactor.JimeiuniversityThereforetheexciterinmaint106Thespeedchangeoftheprimemover(原动机)mustalsobetakenintoaccount(考虑到).JimeiuniversityThespeedchangeoftheprime107Handcontrolofexcitation(励磁)isdifficultsouseismadeofanautomaticvoltageregulator(AVR).JimeiuniversityHandcontrolofexcitation(励磁)108TheAVRconsists

basically

ofacircuitfedfromthealternatoroutputvoltagewhich

detects

smallchangesinvoltageandJimeiuniversityTheAVRconsistsbasicallyof109andfeedsasignaltoanamplifier(放大器)whichchangestheexcitationtocorrectthevoltage.Jimeiuniversityandfeedsasignaltoanampli110Stabilizingfeaturesarealsoincorporatedinthecircuitstoavoid‘hunting(振荡)’(constantvoltagefluctuations(波动))orovercorrecting(过调).JimeiuniversityStabilizingfeaturesarealso111Thestaticallyexcitedalternatorhasastaticexcitationsysteminsteadofad.c.exciter.JimeiuniversityThestaticallyexcitedalterna112Thistypeofalternatorwillmoreacceptthesuddenloadingbydirecton-line(轴带的,联机的)startingoflargesquirrelcagemotors(鼠笼式电机).JimeiuniversityThistypeofalternatorwillm113Thestaticexcitationsystemusestransformers(变压器)andrectifiers(整流器)toprovideseries(串激)andshunt(并激)componentsforthealternatorfield,JimeiuniversityThestaticexcitationsystemu114thatis,itiscompounded(复激励的).Jimeiuniversitythatis,itiscompounded(复激励的115Brushesandslipringsareusedtotransferthecurrenttothefield

coils

whicharemountedontherotor.JimeiuniversityBrushesandslipringsareused116Theterminalvoltagefromthealternatorthusgivestheno-loadvoltageandJimeiuniversityTheterminalvoltagefromthe117andtheloadcurrentprovidestheextraexcitationtogiveasteadyvoltageunderanyloadcondition.Jimeiuniversityandtheloadcurrentprovides118Thecompensation

necessaryforspeedvariationrequiresthatavoltageregulatorisalsobuiltintothesystem.JimeiuniversityThecompensationnecessaryfor119Thebrushlesshighspeedalternatorwasalsodevelopedtoeliminate(取消、消除)

d.c.exciterswiththeirassociatedcommutators(整流子)andbrushgear(电刷机构).JimeiuniversityThebrushlesshighspeedalter120Thealternatorandexciterrotorsareonacommonshaft,whichalsocarriestherectifiers.JimeiuniversityThealternatorandexciterrot121Theexciteroutputisfedtotherectifiersandthenthroughconductorsinthehollowshafttothealternatorfieldcoils.JimeiuniversityTheexciteroutputisfedtot122Anautomaticvoltageregulatorisusedwiththistypeofalternator.JimeiuniversityAnautomaticvoltageregulator123ReadingMaterialParalleloperationofgenerators(发电机的并联运行)JimeiuniversityReadingMaterialParalleloper124Threephasesalternatorsarrangedforparalleloperationrequireaconsiderableamountofinstrumentations.JimeiuniversityThreephasesalternatorsarran125Thiswillincludeammeters,wattmeter,voltmeter,frequencymeterandasynchronizingdevice(同步装置).JimeiuniversityThiswillincludeammeters,wa126Reversepowerprotection(逆功率保护)isprovidedtoalternatorssincereversecurrentprotectioncannotbeused.JimeiuniversityReversepowerprotection(逆功率保护127Alternativelyvarioustrips(跳闸机构)maybeprovidedintheeventof

primemover(发动机)failuretoensurethatthealternatordoesnotactasamotor.JimeiuniversityAlternativelyvarioustrips(跳闸128Theoperationofparallelingtwoalternatorsrequiresthevoltagestobeequalandalsoinphase.JimeiuniversityTheoperationofparallelingt129Thealternatingcurrentoutputofanymachineisalwayschanging,JimeiuniversityThealternatingcurrentoutput130sofortwomachinestooperatetogether

theirvoltagesmustbechangingatthesamerate

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