变压器基本知识英文Word文档格式.docx
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变压器基本知识英文Word文档格式.docx
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Thetransformerisastaticelectricdevicewhichcantransformalternativevoltageandcurrenttotransferelectricpowerinsamefrequencybetweentwoormorewindingsbymeansofelectromagneticinduction.
Thetransformerhasalotofuses.Therearevariouskindsoftransformerswidelyusedinalldepartmentsofnationaleconomy.Inviewoftheanglefromtheelectricpowersystem,anelectricpowernetworkconnectsmanypowerplantsandusersandtheelectricenergygeneratedfromtheelectricpowernetworkshallbealwayssenttouserareasbytransmissioninlongdistance.Incasetheelectricpowertobetransferredisconstant,thehigherthetransferredvoltage,thelessthecurrenttobeneededbecausethevoltagedropisindirectproportionwiththecurrentandthelossofelectricenergyisindirectproportionwiththesquareofthecurrent.Thereforeitcanlargelyreducethevoltagedropandenergylossofthetransmissionlinesifhighertransferredvoltageisadopted.Atpresentitisdifficulttechnicallytomakethegeneratorwithhighervoltage,alternatively,thestep-uptransformerisusedtoriseupthevoltageattheterminalofthegeneratorbeforetheelectricpowerissent.Thelongerthetransmissiondistance,thelargerthetransferredpowerandthehighertherequirementofvolumeandvoltagelevelsofthetransformer.Astherearealotoflevelsofvoltageexistedinthepowernetwork,itshouldhavetransformerswithdifferentsizesofvoltagetomakeconnection.
Ontheotherhand,whenelectricenergyistransferredtothereceivingterminalitshouldhavethestep-downtransformertoreducethehighvoltageonthetransmissionlinestothevoltageofthepowerdistributionsystem,thenreducethevoltagetothatrequiredbyallelectricequipmentsthroughthedistributiontransformer.
Itcanbeseenthepositionofthetransformerintheelectricpowersystemisvitalimportant.Notonlyitrequiresmuchtransformers,normallythetotalinstallationcapacityoftransformersare8-10timesofthatofthegenerator,butalsoitrequiresthattransformersshouldhavegoodperformances,safeandreliableoperation.
Exceptintheelectricpowersystem,thetransformerisalsousedinindustriesandmineswherespecialpowersupplyisneeded,forexamplethetransformerfortheelectricfurnaceinmetallurgy,thetransformerfortherectificationinelectrolysisorchemicalindustry,thetransformerforelectricwelding,thetransformerfortest,thetransformerfortractioninrailwayandthoseproductsbelongingtothecategoryofthetransformersuchasmutualinductor,reactor,extinctioncoiletc.Astheyhavesimilarbasicprincipleandstructureofthetransformerandmuchapplicationandvarieties,theyarecalledtransformer-likeproducts.
II.ClassificationofTransformer
(1)Classifyaccordingtouse,therearepowertransformer,electricfurnacetransformer,rectificationtransformer,electricweldingtransformer,testtransformer,voltage-regulatingtransformer,reactorandmutualinductoretc.
(2)Classifyaccordingtonumberofoutputphase,therearesingle-phasetransformer,three-phasetransformer.
(3)Classifyaccordingtocoolingmedia,therearedrytransformer,oil-immersedtransformerandairtransformer.
(4)Classifyaccordingtocoolingstyle,thereareoil-immersedself-cooledtransformer,oil-immersedair-cooledtransformer,oil-immersedandforcedoilcirculationair-cooledtransformer,oil-immersedandforcedoilcirculationwater-cooledtransformeranddrytransformer.
(5)Classifyaccordingtonumberofwinding,therearedouble-windingtransformer,three-windingtransformerandautotransformer.
(6)Classifyaccordingtostyleofvoltage-regulating,therearefield-freevoltage-regulatingtransformerandloadvoltage-regulatingtransformer.
(7)Classifyaccordingtostructureofironcore,therearecore-typetransformerandshell-typetransformer.
(8)Classifyaccordingtoinsulationleveloftheneutralpoint,therearefullinsulationtransformerandtapinsulationtransformer.
(9)Classifyaccordingtomaterial,therearecopperwiretransformerandaluminumwiretransformer.
III.ModelandRatedDataofTransformer
1.ModelofTransformer
Thevariouskindsofclassificationofthetransformercannotcoverallcharacteristicsofthetransformer.Itshouldhavethemodelofproducttoexpressallitcharacteristic.ThemodelofthetransformerconsistsoftheChinesephoneticalphabetsandArabicnumeralsandeachalphabetordigitstandsforacertainmeaning.
SFSRNZ-□/□
Voltagelevelofhighvoltagewinding(kV)
Ratedcapacity(kVA)
Voltage–regulatingstyle:
itmeansloadvoltage-regulatingifitappearsotherwiseitmeansfield-freevoltage-regulating
“Resisting”hightemperature(itmeansclassFinsulationtemperature
Insulation(cooling)mediaishard“burning”oil
Numberofwindings:
itmeansthreewindingsifitappearsotherwiseitmeansdoublewindings
Coolingstyle:
itmeansair-coolingifitappearsotherwiseitmeansselfcooling
Three-phasetransformer
Exampleofthemodeloftheelectricpowertransformerproduct:
SRNZ-25000/33meansthree-phaseloadvoltage-regulatinghightemperatureresistingliquid-immersedself-cooleddouble-windingpowertransformerwiththeratedhighvoltageof33kVandtheratedcapacityof25000kVA.
2.RatedDataoftheTransformer
(1)TheratedvoltageU1N/U2Nwiththeunitofkilovolt(kV).Forthethree-phasetransformertheratedvoltagemeansthelinearvoltage.
(2)TheratedcurrentI1N/I2Nwiththeunitofampere(A).Forthethree-phasetransformertheratedcurrentmeansthelinearcurrent.
(3)TheratedcapacitySN,i.e.theapparentpowerwiththeunitofkilovolt-ampere(kVA).Ithasrelationswiththeratedvoltageandtheratedcurrentasfollows:
Thesingle-phasetransformerSN=U1NI1N;
SN=U2NI2N
Thethree-phasetransformerSN=U1NI1N;
Theratedcapacityofthetransformeristheguaranteedvalueoftheoutputcapacityofthetransformer.Itisdifferentwiththeratedcapacityofthewinding.Theratedcapacityofthedouble-windingtransformeristheratedcapacityofthewindingwhileforthemultiplewindingstransformer,theratedcapacityofeachwindingshouldbespecifiedanditsratedcapacityistheratedcapacityofthemaximumwinding.
InourcountrytheleveloftheratedcapacityofthetransformerisR10preferrednumbersincreasedbythetimesof,onlythatof30kVAandthoseof63000kVAandupwardsaredifferentwithpreferrednumbers.ThelevelsofdetailedcapacitiesareshowninTable1-3.
Table1-3LevelsofRatedCapacitiesofTransformerUnit:
kVA
10
20
(30)
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
25000
31500
40000
50000
63000
(90000)
(120000)
(150000)
(180000)
(240000)
(360000)
Note:
Thesingle-phasetransformertobeconsistedinthethree-phasetransformersethasonly1/3ofthevaluesinthetablewhilethesingle-phasetransformerforotherusehasthesamevaluesinthetable.
(4)TheratedfrequencyfwiththeunitofHertz(Hz).Inourcountrythemainfrequencyis50Hz.
(5)Theunloadcurrentandunloadloss.Whenthesecondarywindingofthetransformerisopenandtheprimarywindingisappliedbytheratedvoltagewiththeratedfrequencyofsinusoidalwave,thecurrentpassingthroughitiscalledastheunloadcurrentI0.Normallytheunloadcurrentisexpressedbythepercentageoftheratedcurrent.Theactivepowergeneratedwhenthetransformerisoperatedunderno-loadiscalledasunloadlossP0.
(6)Reactancevoltageandloadloss.Whenthesecondarywindingofthetransformerisinshortcircuit,thevoltageappliedupontheprimarywindingtogeneratetheratedcurrenttoflowthroughiscalledasthereactancevoltageUk.Normallythereactancevoltageisexpressedbythepercentageoftheratedvoltage.ThecausedlosscorrespondingtotheratedcapacityunderthereferencetemperatureiscalledastheloadlossPk.
Inaddition,thenameplateofthetransformeralsoshowsnumberofphases,wiringdiagramandgroupstobeconnected,operationstyleandcoolingstyle,totalweightofthetransformer,totalweightofoiletc.
I.BasicElectromagneticLaw
1.LawofElectromagneticInduction
SupposeacoilofNturnsinthemagneticfield,incasethemagneticfluxφintercrossedwiththecoilchanges,the
inducedelectromotiveforceshallbegeneratedinthecoil.Ifthesupposeddirectionofthe
inducedelectromotiveforceandthepositivedirectionofintercrossedmagneticfluxareinaccordancewiththeright-handscrewrule,thentheinducedelectromotiveforceis:
(2-1)
inwhiche—the
inducedelectromotiveforce,V;
N— numberofturnsofthecoil;
dΦ—changeofthemagneticfluxinthecoil,Wb;
dt—timerequiredbythechangeofmagneticlinesofflux,s.
2.MagneticInductionIntensity(magneticfluxdensity)
Themagneticinductionintensitymeansthenumberofmagneticlinesoffluxpassingthroughtheverticalunitarea.Itisusedtojudgeifnumberofthemagneticlinesoffluxisstrongornot.Thecalculationformulaisshownasfollows:
(2-2)
Inwhich,B—magneticinductionintens
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