負載變壓器與直流電機外文文獻翻譯

負載變壓器與直流電機外文文獻翻譯(含：英文原文及中文譯文)文獻出處：BMirafzal.TheTransformeronload﹠IntroductiontoDCMachines[J].JournalofMaterialsProcessingTechnology,2013,2(3):112-118.英文原文TheTransformeronload﹠IntroductiontoDCMachinesBMirafzalIthasbeenshownthataprimaryinputvoltage1Vcanbetransformedtoanydesiredopen-circuitsecondaryvoltage2Ebyasuitablechoiceofturnsratio.2Eisavailableforcirculatingaloadcurrentimpedance.Forthemoment,alaggingpowerfactorwillbeconsidered.Thesecondarycurrentandtheresultingampere-turns22NIwillchangetheflux,tendingtodemagnetizethecore,reducemΦandwithit1E.Becausetheprimaryleakageimpedancedropissolow,asmallalterationto1Ewillcauseanappreciableincreaseofprimarycurrentfrom0Itoanewvalueof1Iequalto()()ijXREV++111/.Theextraprimarycurrentandampere-turnsnearlycancelthewholeofthesecondaryampere-turns.Thisbeingso,themutualfluxsuffersonlyaslightmodificationandrequirespracticallythesamenetampere-turns10NIasonnoload.Thetotalprimaryampere-turnsareincreasedbyanamount22NInecessarytoneutralizethesameamountofsecondaryampere-turns.Inthevectorequation,102211NININI=+;alternatively,221011NININI-=.Atfullload,thecurrent0Iisonlyabout5%ofthefull-loadcurrentandso1Iisnearlyequalto122/NNI.Becauseinmindthat2121/NNEE=,theinput2kVAwhichisapproximately11IEisalsoapproximatelyequaltotheoutputkVA,22IE.Thephysicalcurrenthasincreased,andwithintheprimaryleakagefluxtowhichitisproportional.Thetotalfluxlinkingtheprimary,111Φ=Φ+Φ=Φmp,isshownunchangedbecausethetotalbacke.m.f.,(dtdNE/111Φ-)isstillequalandoppositeto1V.However,therehasbeenaredistributionoffluxandthemutualcomponenthasfallenduetotheincreaseof1Φwith1I.Althoughthechangeissmall,thesecondarydemandcouldnotbemetwithoutamutualfluxande.m.f.alterationtopermitprimarycurrenttochange.ThenetfluxsΦlinkingthesecondarywindinghasbeenfurtherreducedbytheestablishmentofsecondaryleakagefluxdueto2I,andthisopposesmΦ.AlthoughmΦand2Φareindicatedseparately,theycombinetooneresultantinthecorewhichwillbedownwardsattheinstantshown.ThusthesecondaryterminalvoltageisreducedtodtdNVS/22Φ-=whichcanbeconsideredintwocomponents,i.e.dtdNdtdNVm//2222Φ-Φ-=orvectorially2222IjXEV-=.Asfortheprimary,2Φisresponsibleforasubstantiallyconstantsecondaryleakageinductance222222/Λ=ΦNiN.Itwillbenoticedthattheprimaryleakagefluxisresponsibleforpartofthechangeinthesecondaryterminalvoltageduetoitseffectsonthemutualflux.Thetwoleakagefluxesarecloselyrelated;2Φ,forexample,byitsdemagnetizingactiononmΦhascausedthechangesontheprimarysidewhichledtotheestablishmentofprimaryleakageflux.Ifalowenoughleadingpowerfactorisconsidered,thetotalsecondaryfluxandthemutualfluxareincreasedcausingthesecondaryterminalvoltagetorisewithload.pΦisunchangedinmagnitudefromthenoloadconditionsince,neglectingresistance,itstillhastoprovideatotalbacke.m.f.equalto1V.Itisvirtuallythesameas11Φ,thoughnowproducedbythecombinedeffectofprimaryandsecondaryampere-turns.Themutualfluxmuststillchangewithloadtogiveachangeof1Eandpermitmoreprimarycurrenttoflow.1Ehasincreasedthistimebutduetothevectorcombinationwith1Vthereisstillanincreaseofprimarycurrent.Twomorepointsshouldbemadeaboutthefigures.Firstly,aunityturnsratiohasbeenassumedforconveniencesothat'21EE=.Secondly,thephysicalpictureisdrawnforadifferentinstantoftimefromthevectordiagramswhichshow0=Φm,ifthehorizontalaxisistakenasusual,tobethezerotimereference.Thereareinstantsinthecyclewhen3primaryleakagefluxiszero,whenthesecondaryleakagefluxiszero,andwhenprimaryandsecondaryleakagefluxiszero,andwhenprimaryandsecondaryleakagefluxesareinthesamesense.Theequivalentcircuitalreadyderivedforthetransformerwiththesecondaryterminalsopen,caneasilybeextendedtocovertheloadedsecondarybytheadditionofthesecondaryresistanceandleakagereactance.Practicallyalltransformershaveaturnsratiodifferentfromunityalthoughsuchanarrangementissometimesemployedforthepurposesofelectricallyisolatingonecircuitfromanotheroperatingatthesamevoltage.Toexplainthecasewhere21NN≠thereactionofthesecondarywillbeviewedfromtheprimarywinding.Thereactionisexperiencedonlyintermsofthemagnetizingforceduetothesecondaryampere-turns.Thereisnowayofdetectingfromtheprimarysidewhether2Iislargeand2Nsmallorviceversa,itistheproductofcurrentandturnswhichcausesthereaction.Consequently,asecondarywindingcanbereplacedbyanynumberofdifferentequivalentwindingsandloadcircuitswhichwillgiverisetoanidenticalreactionontheprimary.Itisclearlyconvenienttochangethesecondarywindingtoanequivalentwindinghavingthesamenumberofturns1Nastheprimary.Thereareafewcheckswhichcanbemadetoseeiftheprocedureoutlinedisvalid.Forexample,thecopperlossinthereferredsecondarywindingmustbethesameasintheoriginalsecondaryotherwisetheprimarywouldhavetosupplyadifferentlosspower.Theargumentissound,thoughatfirstitmayhaveseemedsuspect.Infact,iftheactualsecondarywindingwasremovedphysicallyfromthecoreandreplacedbytheequivalentwindingandloadcircuitdesignedtogivetheparameters1N,'2R,'2Xand'2I,measurementsfromtheprimaryterminalswouldbeunabletodetectanydifferenceinsecondaryampere-turns,kVAdemandorcopperloss,undernormalpowerfrequencyoperation.Theequivalentcircuitforthegeneralcasewhere21NN≠exceptthatmrhasbeenaddedtoallowforironlossandanideallosslesstransformationhasbeenincludedbeforethesecondaryterminalstoreturn'2Vto2V.Allcalculationsofinternalvoltageandpowerlossesaremadebeforethisidealtransformationisapplied.Thebehaviourofatransformerasdetectedatbothsetsofterminalsisthesameasthebehaviourdetectedatthecorrespondingterminalsofthiscircuitwhentheappropriateparametersareinserted.Theslightlydifferentrepresentationshowingthecoils1Nand2Nsidebysidewithacoreinbetweenisonlyusedforconvenience.Onthetransformeritself,thecoilsare,ofcourse,woundroundthesamecore.Itshouldbepointedoutthattheequivalentcircuitasderivedhereisonlyvalidfornormaloperationatpowerfrequencies;capacitanceeffectsmustbetakenintoaccountwhenevertherateofchangeofvoltagewouldgiverisetoappreciablecapacitancecurrents,dtCdVIc/=.Theyareimportantathighvoltagesandatfrequenciesmuchbeyond100cycles/sec.Afurtherpointisnottheonlypossibleequivalentcircuitevenforpowerfrequencies.Analternative,treatingthetransformerasathree-orfour-terminalnetwork,givesrisetoarepresentationwhichisjustasaccurateandhassomeadvantagesforthecircuitengineerwhotreatsalldevicesascircuitelementswithcertaintransferproperties.Thecircuitonthisbasiswouldhaveaturnsratiohavingaphaseshiftaswellasamagnitudechange,andtheimpedanceswouldnotbethesameasthoseofthewindings.Thecircuitwouldnotexplainthephenomenawithinthedeviceliketheeffectsofsaturation,soforanunderstandingofinternalbehaviour.Therearetwowaysoflookingattheequivalentcircuit:(a)viewedfromtheprimaryasasinkbutthereferredloadimpedanceconnectedacross'2V,or(b)viewedfromthesecondaryasasourceofconstantvoltage1Vwithinternaldropsdueto1Reand1Xe.Themagnetizingbranchissometimesomittedinthisrepresentationandsothecircuitreducestoageneratorproducingaconstantvoltage1E(actuallyequalto1V)andhavinganinternalimpedancejXR+(actuallyequalto11RejXe+).Ineithercase,theparameterscouldbereferredtothesecondarywindingandthismaysavecalculationtime.Theresistancesandreactancescanbeobtainedfromtwosimplelightloadtests.IntroductiontoDCMachinesDCmachinesarecharacterizedbytheirversatility.Bymeansofvariouscombinationofshunt,series,andseparatelyexcitedfieldwindingstheycanbedesignedtodisplayawidevarietyofvolt-ampereorspeed-torquecharacteristicsforbothdynamicandsteadystateoperation.Becauseoftheeasewithwhichtheycanbecontrolled,systemsofDCmachinesareoftenusedinapplicationsrequiringawiderangeofmotorspeedsorprecisecontrolofmotoroutput.TheessentialfeaturesofaDCmachineareshownschematically.Thestatorhas6salientpolesandisexcitedbyoneormorefieldcoils.Theair-gapfluxdistributioncreatedbythefieldwindingissymmetricalaboutthecenterlineofthefieldpoles.Thisaxisiscalledthefieldaxisordirectaxis.Asweknow,theACvoltagegeneratedineachrotatingarmaturecoilisconvertedtoDCintheexternalarmatureterminalsbymeansofarotatingcommutatorandstationarybrushestowhichthearmatureleadsareconnected.Thecommutator-brushcombinationformsamechanicalrectifier,resultinginaDCarmaturevoltageaswellasanarmaturem.m.f.wavewhichisfixedinspace.Thebrushesarelocatedsothatcommutationoccurswhenthecoilsidesareintheneutralzone,midwaybetweenthefieldpoles.Theaxisofthearmaturem.m.f.wavethenin90electricaldegreesfromtheaxisofthefieldpoles,i.e.,inthequadratureaxis.Intheschematicrepresentationthebrushesareshowninquaratureaxisbecausethisisthepositionofthecoilstowhichtheyareconnected.Thearmaturem.m.f.wavethenisalongthebrushaxisasshown..(Thegeometricalpositionofthebrushesinanactualmachineisapproximately90electricaldegreesfromtheirpositionintheschematicdiagrambecauseoftheshapeoftheendconnectionstothecommutator.)Themagnetictorqueandthespeedvoltageappearingatthebrushesareindependentofthespatialwaveformofthefluxdistribution;forconvenienceweshallcontinuetoassumeasinusoidalflux-densitywaveintheairgap.Thetorquecanthenbefoundfromthemagneticfieldviewpoint.Thetorquecanbeexpressedintermsoftheinteractionofthedirect-axisair-gapfluxperpoledΦandthespace-fundamentalcomponent1aFofthearmaturem.m.f.wave.Withthebrushesinthequadratureaxis,theanglebetweenthesefieldsis90electricaldegrees,anditssineequalsunity.ForaPpolemachine12)2(2adFPT?π=Therectifiedvoltagegeneratedinthearmaturehasalreadybeendiscussedbeforeforanelementarysingle-coilarmature.Theeffectofdistributingthewindinginseveralslotsisshowninfigure,inwhicheachoftherectifiedsinewavesisthevoltagegeneratedinoneofthecoils,commutationtakingplaceatthemomentwhenthecoilsidesareintheneutralzone.Thegeneratedvoltageasobservedfromthebrushesisthesumoftherectifiedvoltagesofallthecoilsinseriesbetweenbrushesandisshownbytheripplinglinelabeledaeinfigure.Withadozenorsocommutatorsegmentsperpole,theripplebecomesverysmallandtheaveragegeneratedvoltageobservedfromthebrushesequalsthesumoftheaveragevaluesoftherectifiedcoilvoltages.Therectifiedvoltageaebetweenbrushes,knownalsoasthespeedvoltage,ismdamdaaWKWmPCe??π==2WhereaKisthedesignconstant.Therectifiedvoltageofadistributedwindinghasthesameaveragevalueasthatofaconcentratedcoil.Thedifferenceisthattherippleisgreatlyreduced.Overafairlywiderangeofexcitationthereluctanceoftheironisnegligiblecomparedwiththatoftheairgap.Inthisregionthefluxislinearlyproportionaltothetotalm.m.f.ofthefieldwindings,theconstantofproportionalitybeingthedirect-axisair-gappermeance.TheoutstandingadvantagesofDCmachinesarisefromthewidevarietyofoperatingcharacteristicswhichcanbeobtainedbyselectionofthemethodofexcitationofthefieldwindings.ThefieldwindingsmaybeseparatelyexcitedfromanexternalDCsource,ortheymaybeself-excited;i.e.,themachinemaysupplyitsownexcitation.Themethodofexcitationprofoundlyinfluencesnotonlythesteady-statecharacteristics,butalsothedynamicbehaviorofthemachineincontrolsystems.Theconnectiondiagramofaseparatelyexcitedgeneratorisgiven.Therequiredfieldcurrentisaverysmallfractionoftheratedarmaturecurrent.Asmallamountofpowerinthefieldcircuitmaycontrolarelativelylargeamountofpowerinthearmaturecircuit;i.e.,thegeneratorisapoweramplifier.Separatelyexcitedgeneratorsareoftenusedinfeedbackcontrolsystemswhencontrolofthearmaturevoltageoverawiderangeisrequired.Thefieldwindingsofself-excitedgeneratorsmaybesuppliedinthreedifferentways.Thefieldmaybeconnectedinserieswiththearmature,resultinginashuntgenerator,orthefieldmaybeintwosections,oneofwhichisconnectedinseriesandtheotherinshuntwiththearmature,resultinginacompoundgenerator.Withself-excitedgeneratorsresidualmagnetismmustbepresentinthemachineirontogettheself-excitationprocessstarted.Inshuntandseparatelyexcitedmotorsthefieldfluxisnearlyconstant.Consequently,increasedtorquemustbeaccompaniedbyaverynearlyproportionalincreaseinarmaturecurrentandhencebyasmalldecreaseincountere.m.f.toallowthisincreasedcurrentthroughthesmallarmatureresistance.Sincecountere.m.f.isdeterminedbyfluxandspeed,thespeedmustdropslightly.Likethesquirrel-cageinductionmotor,theshuntmotorissubstantiallyaconstant-speedmotorhavingabout5percentdropinspeedfromnoloadtofullload.Startingtorqueandmaximumtorquearelimitedbythearmaturecurrentthatcanbecommutatedsuccessfully.Anoutstandingadvantageoftheshuntmotoriseaseofspeedcontrol.Witharheostatintheshunt-fieldcircuit,thefieldcurrentandfluxperpolecanbevariedatwill,andvariationoffluxcausestheinversevariationofspeedtomaintaincountere.m.f.Intheseriesmotor,increaseinloadisaccompaniedbyincreaseinthearmaturecurrentandm.m.f.andthestatorfieldflux(providedtheironisnotcompletelysaturated).Becausefluxincreaseswithload,speedmustdropinordertomaintainthebalancebetweenimpressedvoltageandcountere.m.f.;moreover,theincreaseinarmaturecurrentcausedbyincreasedtorqueissmallerthanintheshuntmotorbecauseoftheincreasedflux.Theseriesmotoristhereforeavarying-speedmotorwithamarkedlydroopingspeed-loadcharacteristic.Forapplicationsrequiringheavytorqueoverloads,thischaracteristicisparticularlyadvantageousbecausethecorrespondingpoweroverloadsareheldtomorereasonablevaluesbytheassociatedspeeddrops.Veryfavorablestartingcharacteristicsalsoresultfromtheincreaseinfluxwithincreasedarmaturecurrent.Inthecompoundmotortheseriesfieldmaybeconnectedeithercumulatively,sothatits.m.m.f.addstothatoftheshuntfield,ordifferentially,sothatitopposes.Thedifferentialconnectionisveryrarelyused.Acumulativelycompoundedmotorhasspeed-loadcharacteristicintermediatebetweenthoseofashuntandaseriesmotor,thedropofspeedwithloaddependingontherelativenumberofampere-turnsintheshuntandseriesfields.Itdoesnothavethedisadvantageofveryhighlight-loadspeedassociatedwithaseriesmotor,butitretainstoaconsiderabledegreetheadvantagesofseriesexcitation.TheapplicationadvantagesofDCmachineslieinthevarietyofperformancecharacteristicsofferedbythepossibilitiesofshunt,series,andcompoundexcitation.Someofthesecharacteristicshavebeentoucheduponbrieflyinthisarticle.Stillgreaterpossibilitiesexistifadditionalsetsofbrushesareaddedsothatothervoltagescanbeobtainedfromthecommentator.ThustheversatilityofDCmachinesystemsandtheiradaptabilitytocontrol,bothmanualandautomatic,aretheiroutstandingfeatures.中文譯文負載變壓器和直流電機介紹BMirafzal研究已經(jīng)表明，通過適當選擇匝數(shù)比，主輸入電壓1V可以變換為任何期望的開路次級電壓2E。2E可用于循環(huán)負載電流阻抗。目前，將考慮滯后功率因數(shù)。次級電流和所產(chǎn)生的安匝數(shù)22NI將改變磁通量，傾向于去磁芯，減小mΦ并與1E一起。因為初級泄漏阻抗下降很小，所以1E的小改動將導致初級電流從0I明顯增加到1I的新值，等于（）（）ijXREV++111/。額外的初級電流和安培匝數(shù)幾乎消除了整個次級安培-轉(zhuǎn)數(shù)。這樣，相互通量只受到輕微的修改，并且實際上需要與無負載時相同的凈安匝數(shù)10NI。為了中和相同數(shù)量的二次安培匝數(shù)，總的主安匝數(shù)增加了22N。在向量方程中，102211NININI=+;或者，221011N我N我N-=。在滿載情況下，電流0I僅為滿載電流的5％左右，因此1I幾乎等于122/NNI。因為考慮到2121/NNEE=，輸入2kVA約為11IE也近似等于輸出kVA，22IE。物理電流增加了，并且與其成正比的初級漏磁通量也增加了。連接初級111φ=Φ+Φ=Φmp的總磁通量表示為不變，因為總的后電流fm，（dtdNE/111Φ-）仍然與1V相等并相反。然而，由于1I增加1Φ，磁通重新分配，相互成分下降。雖然變化很小，但如果沒有相互交流和e.m.f.，二次需求就無法實現(xiàn)。改變以允許原電流改變。通過建立由2I引起的次級漏磁通量，進一步減小了與次級繞組相連的凈磁通量φ，這與mΦ相反。盡管mΦ和2Φ分別表示，但它們在核心中結(jié)合成一個結(jié)果，在所示瞬間向下結(jié)果。因此，次級終端電壓降為dtdNVS/22Φ-=這可以考慮為兩個分量，即dtdNdtdNVm//2222Φ-Φ-=或者矢量2222IjXEV-=。對于初級，2Φ負責基本不變的次級漏感222222/Λ=ΦNiN。將會注意到，由于其對相互通量的影響，初級漏磁通量負責次級端電壓的部分變化。兩種泄漏通量密切相關(guān);2Φ，例如，由于它對mΦ的消磁作用，導致初級側(cè)的變化導致初級漏磁通的建立。如果考慮到足夠低的前導功率因數(shù)，則總次級磁通量和相互磁通量增加，導致次級端電壓隨著負載而升高。ΦΦ在空載條件下的量值不變，因為忽略電阻，它仍然必須提供總后向電流。等于1V。它與11Φ幾乎相同，但現(xiàn)在由主安培和次安培的組合效應(yīng)產(chǎn)生。相互通量仍然必須隨著負載而改變，以改變1E并允許更多的初級電流流動。1E這次增加了，但由于與1V的向量組合，初級電流仍然增加。應(yīng)該對這些數(shù)字再提兩點。首先，為了方便已經(jīng)假設(shè)了單位圈數(shù)比，以便'21EE=。其次，如果橫軸取平常值，則從顯示0=Φm的矢量圖中繪制物理圖片的不同時刻，作為零時間參考。當三次漏磁通為零，二次漏磁通為零時，以及一次漏磁通量為零時，以及一次漏磁通量與次漏磁通量具有相同意義時，循環(huán)中有時刻。已經(jīng)為次級終端打開的變壓器推導出的等效電路可以很容易地擴展到通過增加次級電阻和漏電抗來覆蓋負載次級。實際上所有的變壓器都具有不同于1的匝數(shù)比，盡管這樣的布置有時被用于將一個電路與另一個電路在相同電壓下操作的電路隔離。為了解釋21NN≠次級反應(yīng)的情況，將從初級繞組來看。僅由于次級安匝所引起的磁化力而經(jīng)歷反應(yīng)。從初級側(cè)無法檢測到2I是大還是小2N，反之亦然，它是電流和匝數(shù)的產(chǎn)物，引起反應(yīng)。因此，次級繞組可以被任何數(shù)量的不同的等效繞組和負載電路所替代，這將在初級繞組上產(chǎn)生相同的反應(yīng)。將次級繞組改變?yōu)榫哂邢嗤褦?shù)1N的等效繞組顯然是方便的作為主要的。有幾項檢查可以查看所列程序是否有效。例如，所提及的次級繞組中的銅損必須與原始次級中的銅損相同，否則主要將不得不提供不同的損耗功率。這個論點很有道理，盡管起初它似乎有些可疑。事實上，如果實際的次級繞組從物理上被移除并且被設(shè)計為給出參數(shù)1N，'2R，'2X和'2I的等效繞組和負載電路代替，則來自主要端子的測量結(jié)果將不能檢測到在正常工頻操作下二次安培匝數(shù)，千伏安需求或銅損的差異。對于21NN≠除mr之外的一般情況，添加了允許鐵損和理想無損變換的一般情況的等效電路已包含在次級端子之前，以使2V返回到2V。所有內(nèi)部電壓和功率損耗的計算均為在應(yīng)用這種理想轉(zhuǎn)換之前做出的。在兩組端子處檢測到的變壓器的行為與在插入適當參數(shù)時在該電路的相應(yīng)端子處檢測到的行為相同。示出線圈1N和2N并排地具有中心之間的稍微不同的表示僅用于方便。在變壓器本身上，線圈當然纏繞在同一個鐵芯上。應(yīng)該指出，這里推導出的等效電路僅適用于工頻正常工作;只要電壓的變化率會引起可觀的電容電流，就必須考慮電容效應(yīng)，dtCdVIc/=。它們在高電壓和頻率超過100次/秒時非常重要。另一點并不是唯一可能的等效電路，即使對于電力頻率也是如此。另一種方法是將變壓器視為三端或四端網(wǎng)絡(luò)，產(chǎn)生的表示同樣準確，并且對于電路工程師來說具有某些優(yōu)點將所有設(shè)備視為具有某些傳輸屬性的電路元件。在此基礎(chǔ)上的電路將具有具有相移以及幅度變化的匝數(shù)比，并且阻抗不會與繞組的相同。該電路不會像飽和度的影響那樣解釋器件內(nèi)部的現(xiàn)象，因此了解內(nèi)部行為。有兩種方法查看等效電路：（a）從主電源看為接收器，但所提到的負載阻抗連接在2V或2V之間（b）從次級視角看，1V和1Xe引起的內(nèi)部壓降為1V的恒定電壓源。在這種表示中有時省略了磁化支路，因此電路減少到產(chǎn)生恒定電壓1E（實際上等于1V）并且具有內(nèi)部阻抗jXR+（實際上等于11RejXe+）的發(fā)生器。無論哪種情況，參數(shù)都可以被稱為次級繞組，這可以節(jié)省計算時間。電阻和電