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1、2.TRANSFORMERSTransformersarecommonlyusedinapplicationswhichrequiretheconversionofACvoltagefromonevoltageleveltoanother.Therearetwobroadcategoriesoftransformers:electronictransformers,whichoperateatverylowpowerlevels,andpowertransformers,whichprocessthousandsofwattsof
2、power.Electronictransformersareusedinconsumerelectronicequipmentliketelevisionsets,VCRs,CDplayers,personalcomputers,andmanyotherdevices,toreducethelevelofvoltagefrom220V(availablefromtheACmains)tothedesiredlevelatwhichthedeviceoperates.Powertransformersareusedinpowerg
3、eneration,transmissionanddistributionsystemstoraiseorlowerthelevelofvoltagetothedesiredlevels.Thebasicprincipleofoperationofbothtypesoftransformersisthesame.Inthischapter,wewillfirstreviewsomeofthebasicconceptsofmagneticcircuits,whicharefundamentalbuildingblocksintran
4、sformersandelectricmachinery.Inordertounderstandhowatransformeroperates,wewillexaminetwoinductorsthatareplacedincloseproximitytooneanother.Theconceptsofsuchmagneticcoupledcircuitswillbeextendedtothedevelopmentoftransformers.Afterunderstatingtherelationshipsbetweenvolt
5、agesandcurrents,wewilllookatsomepracticalconsiderationsregardingtheuseoftransformers.Themainlearningobjectivesforthischapterarelistedbelow.LearningObjectives:UnderstandconceptofmutualinductanceUnderstandoperationofidealtransformers.Useequivalentcircuitstodeterminev
6、oltagesandcurrents.Analyzetheoperationoftransformerfordifferenttransformationratios.Understandtheconceptofareflectedloadinatransformer,anditsapplicationinimpedancematching.Studytheapplicationoftransformersinelectricalenergydistributionandpowersupplies.Recommendedte
7、xtforthissectionofthecourse:(i)AllanR.Hambley,ElectricalEngineeringPrinciplesandApplications,Chapter15.(ii)GiorgioRizzoni,PrinciplesandApplicationsofElectricalEngineering,Chapter16.12TransformersMagneticFieldandMutualInductance:Reviewofbasicconcepts(Pleasenotethatthes
8、econceptsarecoveredindetailinthePhysicsmodule,andthereforewillnotbediscussedindetailinEG1108.Thebasicterminologyis,however,b