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1、TheTransformeronload﹠IntroductiontoDCMachinesTheTransformeronloadIthasbeenshownthataprimaryinputvoltagecanbetransformedtoanydesiredopen-circuitsecondaryvoltagebyasuitablechoiceofturnsratio.isavailableforcirculatingaloadcurrentimpedance.Forthemoment,alaggingpowe
2、rfactorwillbeconsidered.Thesecondarycurrentandtheresultingampere-turnswillchangetheflux,tendingtodemagnetizethecore,reduceandwithit.Becausetheprimaryleakageimpedancedropissolow,asmallalterationtowillcauseanappreciableincreaseofprimarycurrentfromtoanewvalueofequ
3、alto.Theextraprimarycurrentandampere-turnsnearlycancelthewholeofthesecondaryampere-turns.Thisbeingso,themutualfluxsuffersonlyaslightmodificationandrequirespracticallythesamenetampere-turnsasonnoload.Thetotalprimaryampere-turnsareincreasedbyanamountnecessarytone
4、utralizethesameamountofsecondaryampere-turns.Inthevectorequation,;alternatively,.Atfullload,thecurrentisonlyabout5%ofthefull-loadcurrentandsoisnearlyequalto.Becauseinmindthat,theinputkVAwhichisapproximatelyisalsoapproximatelyequaltotheoutputkVA,.Thephysicalcurr
5、enthasincreased,andwithintheprimaryleakagefluxtowhichitisproportional.Thetotalfluxlinkingtheprimary,,isshownunchangedbecausethetotalbacke.m.f.,()isstillequalandoppositeto.However,therehasbeenaredistributionoffluxandthemutualcomponenthasfallenduetotheincreaseofw
6、ith.Althoughthechangeissmall,thesecondarydemandcouldnotbemetwithoutamutualfluxande.m.f.alterationtopermitprimarycurrenttochange.Thenetfluxlinkingthesecondarywindinghasbeenfurtherreducedbytheestablishmentofsecondaryleakagefluxdueto,andthisopposes.Althoughandarei
7、ndicatedseparately,theycombinetooneresultantinthecorewhichwillbedownwardsattheinstantshown.Thusthesecondaryterminalvoltageisreducedtowhichcanbeconsideredintwocomponents,i.e.orvectorially.Asfortheprimary,isresponsibleforasubstantiallyconstantsecondaryleakageindu
8、ctance.Itwillbenoticedthattheprimaryleakagefluxisresponsibleforpartofthechangeinthesecondaryterminalvoltageduetoitseffectsonthemutualflux.Thetwoleakagefluxesarecloselyrelate