非晶合金铁芯Word格式.docx

非晶合金铁芯Word格式.docx

《非晶合金铁芯Word格式.docx》由会员分享，可在线阅读，更多相关《非晶合金铁芯Word格式.docx（11页珍藏版）》请在冰豆网上搜索。

rioFreireI

IDepartamentodeEngenhariaElé

trica,UniversidadeFederaldeCampinaGrande-UFCG,RuaAprí

gioVeloso,882,CEP58429-900,CampinaGrande,PB,Brasil 

IICompanhiadeEnergiaElé

tricadoEstadodeTocantins,Palmas,TO,Brasil

ABSTRACT

Inthispaperarepresentedsomeconsiderationsabouttheperformanceofsinglewireearthreturnamorphousalloycoretransformersincomparisonwithconventionalsiliconsteelsheetscorestransformersusedinruralelectricenergydistributionnetwork.Ithasbeenrecognizedthatamorphousmetalcoretransformersimproveelectricalpowerdistributionefficiencybyreducingtransformercorelosses.Thisreductionisduetosomeelectromagneticpropertiesoftheamorphousalloyssuchas:

highmagneticpermeability,highresistivity,andlowcoercivity.Experimentalresultsobtainedwithsomesingle-phase,60 

Hz,5 

kVAamorphouscoretransformersinstalledinaruralareaelectricdistributionsysteminNorthernBrazilhavebeenconfirmingtheirsuperiorperformanceincomparisontoidenticalnominalratedtransformersbuiltwithconventionalsiliconsteelcores,particularlywithregardtotheexcitationpowerandtotheno-loadlosses.

Keywords:

amorphousalloy,corelosses,energyefficiency,transformer

1.Introduction

Singlewireearthreturn（SWER）coretransformersarecharacterizedbyhavingonlyonebushingonthehighvoltagesideandtwoormorebushingsonthelowvoltageside.Generally,thesetransformersaredesignedandconstructedtobeusedinruralelectricitydistribution.UsuallySWERcoretransformersarelow-costequipmentandhaveapparentpowerof5,10and15 

kVA.

Thedistributionofelectricitypowerinruralareashasgenerallyhighcostofoperationfortheconcessionarycompaniesduetotheseasonalityoftheirloads.Undertheseconditions,thelossesinthecoresofthetransformersmanufacturedwithconventionalgrainorientedsiliconsteelbecomesignificantwhenthesetransformersoperateinconditionsoflightloadornoload.Insuchcircumstances,partofthetotalcurrentabsorbedbytheelectricsystemisusedinthemagnetizingcoretransformersprocess.However,theselossescanbereduced,whichcanbeachievedbyreplacingtheconventionalbytransformersforamorphousmetal-basedtransformers,becauseithasbeenrecognizedthatamorphousmetalcoretransformersimproveelectricalpowerdistributionefficiencybyreducingexcitationcurrentandcorelosses1.Thisreductionisduetosomeelectromagneticpropertiesoftheamorphousalloyssuchas:

highmagneticpermeability,highresistivity,andlowcoactivity2.

InthispaperarepresentedsomeexperimentalresultsobtainedwithSWER,60 

kVAamorphouscoretransformersinstalledinaruralareaelectricdistributionsystem,distant50 

kmfromPalmas（capitalofthestateofTocantins）,locatedintheAmazonregionofBrazil.

Fromtheseresultsitcanbeobservedthesuperiorperformanceofamorphouscoretransformersincomparisontoidenticaltransformersmanufacturedwithconventionalcold-rolledgrain-oriented（CRGO）siliconsteelcores,particularlywithregardtotheexcitationcurrentandtotheno-loadlosses.Beforebeinginstalled,alltransformersweresubmittedtotestasstatedatBrazilianStandards.

2.FromAcademicResearchtoElectricDistributionSystems

Chronologically,thedevelopmentofamorphousalloyspotentiallyapplicableintransformercoresbeganin1975.However,theintroductionofthesematerialsinthemarketonlyhappenedin1976,withthefirstamorphousmetaldistributiontransformer（AMDT）,builtatMIT'

sLincolnLaboratory（USA）.Inthatopportunity,a30 

kVAtransformerprototype,withanamorphousmaterialcore,wascomparedtoaconventionalsiliconsteelcoretransformerofequalnominalratedpower.Oncethecomparativetestswerecarriedout,theresultsobtainedwerefavorabletoAMDT,particularlyintheaspectsrelativetothelossesandtheexcitationcurrent:

therewasareductionof60%inthetotallosses（87.5%inthecorelossesand21%inthecopperlosses）andtheexcitationcurrentwasreducedfrom2.5to0.12 

A.However,inwhatconcernstheweight,AMDTpresentedanincreaseof15%incomparisontotheconventionalsiliconsteelcoretransformer3.

Intheearly1980'

s,EPRI（ElectricPowerResearchInstitute,USA）andGeneralElectriclaunchedaprojectinwhich25unitsofpre-prototype25 

kVA,15 

kVamorphousmetalcoredistributiontransformers（AMDT）weretestedfortwoyears,followedbydesigningandtesting1000unitsofthesamesizeAMDTsontheirdistributionsystems.Thepurposeofthefieldtrialwastoconferthelong-termstabilityofcorelossinamorphousmetaltransformersunderactualoperationconditions.Tenyearslater,therewasanestimated60000to70000 

AMDTinstalledthroughouttheworld.

InBrazil,thefirststudiesandexperimentaltestshadtheirorigininlaboratoriesofsomedifferentinstitutions,intheearly1990'

s4,passing,soonafter,toassemblybyindustrialmanufacturers5.

3.ExperimentalProcedure

In 

Figure 

1 

areshownsomeunitsof5 

kVASWERtransformerswithamorphousalloycore（Fe78B13Si9）manufacturedbyBrazilianindustriesITB.Seventeenofthesetransformersweresubmittedtoopencircuitandshortcircuittestsinthelaboratoryofthefactory,inJanuary2009.

Thefollowingarelistedthemainelectriccharacteristicsoftransformersundertest:

•Ratedpower 

kVA 

= 

5;

•Phases 

1;

•Frequency 

60 

Hz;

•Highvoltageside（kV）:

20.90to18.19;

•Lowvoltageside（V）:

440/220;

•Ratedcurrentinhighvoltageside:

0.25 

A;

•Ratedcurrentinlowvoltageside:

11.36 

•Subtractivepolarity.

AllroutinetestscarriedoutinaccordancewithspecificBrazilianStandards.Butbecausethemaininterestisdirectlyrelatedtotheenergyefficiencyinthispaperareonlypresentedtwotests:

no-loadandshortcircuit.

4.Results

Table 

arepresentedthecomparativevaluesconcerninglossesandexcitationcurrentinsingle-phase5 

kVAtransformerswithmaximumtension24.2and36.2 

kV,accordingtoBrazilianStandardNBR54406.

Theno-loadlossesandtheexcitationcurrentmeasurementswereperformedatnominalfrequency,applyingratedvoltagetothelowvoltagewindingandleavingthehighvoltageinopencircuit,asrequiredbyBrazilianStandardNBR53567.

2 

arepresentedingraphform,theresultsofcomparativetestsbetweenseventeentransformerswithamorphousalloycoreandseventeentransformerswithCRGOsiliconsteelcore,allwiththesamenominalpowerrating（5 

kVA）.

5.Discussion

Sincetheexcitationcurrentissmall,theJoulelossesinthewindingsarenegligible;

thelossesresultingfromtheprocessofmagnetizationanddemagnetizationofthecorearesignificant.Inanalyticalterms,theselossesarecharacterizedashysteresis,eddycurrentsandanomalouslosses.

Thehysteresislossisdirectlyproportionaltothefrequencyofsupplyvoltageandeddycurrentlossisdirectlyproportionaltothesquareofthefrequencyofthesource.Thisisthereasonwhythistestshouldbeconductedatnominalfrequency.

Physically,thereasonfortheexcitationcurrentissmallcomparedtothenominalcurrentofthewinding,duetothefactthattheno-loadtransformercanberepresentedbyahigh-impedanceloadwithrespecttothepowersupply.Andthisimpedancewillbegreaterthelargerthemagneticpermeabilityandelectricalresistivityofcorematerial.

InthespecificcaseofamorphousFe78B13Si9 

usedinthecoresoftransformersthesevaluesarehigherthanthevaluesforGOFeSialloysusedinconventionaltransformers.Therefore,themaximumrelativemagneticpermeabilityofamorphousFe78B13Si9,60 

Hz,isaround70000,whilethevalueofthisquantityfortheGOFeSiat60 

Hz,isaround40000.SincethevalueoftheelectricalresistivityofamorphousFe78B13Si9 

isbetween130to135 

µ

Ω.m,whilethevalueofthismagnitudefortheGOFeSiisaround10to47 

Ω.m.Notethatthehighvalueofrelativepermeabilityprovidesabettermagneticcouplingandthehighvalueofelectricalresistivityresultsinsmallereddycurrentlossesinthecore.

NotealsothatalthoughbothtransformershavevaluesofexcitationcurrentandloadlossvaluesbelowtheBrazilianStandardNBR 

5440recommended,itappearsthatthevaluesoftheexcitationcurrent（0.13 

A）andno-loadlosses（8 

W）fortransformerswithamorphouscoretransformersarelowerthanvaluesoftheconventionaltransformers,thatare0.36 

Aand36 

W,respectively.

Themeasurementofshortcircuitlosseswasperformedatnominalfrequency,connectingthehighvoltageterminalstothesourceandatthesametimekeepingthelowvoltagewindingsshort-circuited,asshowninFigure 

3.

arepresentedthecomparativevaluesconcerningshort-circuittestinsingle-phase5 

kV,accordingtoBrazilianStandardNBR 

54406.

Ascanbeseenin 

2,therearevirtuallynodifferencesbetweenthevaluesobtainedinshort-circuittestforbothtypesoftransformers.This,infact,wasexpected,sincetheactivelossesrelatetotheJouleeffectinthewindingsandhasnodependenceonthemagneticmaterialcoreandshort-circuitcurrentdependsontheimpedanceofashortcircuit.

Aftersubmittedtoroutinetestsinthelaboratory,theseventeen5 

kVASWERamorphouscoretransformerswereinstalledinaruralareaelectricdistributionsysteminNorthernBrazil,