电气毕业设计外文文献翻译

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1、河南理工大学万方科技学院本科毕业论文附录：外文资料与中文翻译外文资料：SelectionandCoolingofPowerTransformerTheselectionofthetransformercanhaveamajorimpactonthecostofasubstation,sincethetransformerrepresentsthemajorcostitem.Nameplateratingisonlyaguidetotransformerapplication,andshouldonlyb

2、eusedasafirststepintheselectionprocess.Thetransformerisavailableasaself-cooledunit,oritcanbepurchasedwithadditionalstepsofforcedcoolingthatusefanorfansandoilpumps.Thenameplateratingscanbeincreasedfrom25%to66%bytheadditionoffanspumps.Thenameplateratingisb

3、asedonacontinuousloadproducinga550Cto650Cconductortemperatureriseoverambient.Sincemanytransformersdonotcarrycontinuousloads,advantagecanbegainedfromthethermaltimelagtocarryhigherpeakloadswithoutexceedingthetemperaturelimits.Transformerratingsarebasedonth

4、eassumptionthatonlyanextremelyslowdeteriorationofinsulationwilltakeplacewithnormaloperation.Asubstantialincreaseinratingcanbeachievedbyacceleratingthelossofinsulationlife,Thisincreaseinratingmightapproach200%foranhourortwo,andapproximately120%for24hours.

5、Forsubstationsthataredesignedtocarryfullloadundertheoutageofanyonetransformer,ahighemergencyratingfora24-hourperiod(e.g.Untilthefailedunitcanbereplaced)couldmeantheselectionofsmallertransformer河南理工大学万方科技学院本科毕业论文andasubstantialsavinginsubstationcost.These

6、lectionofthetransformershouldinvolveacarefulevaluationofanumberofotherfactors:(1)Impedancesshouldbeselectedconsideringtheireffectonshort-circuitdutiesandlow-sidebreakerratingsbothforinitialandfuturestationdevelopments.Inaddition,impedanceisimportanttoach

7、ieveadivisionintheparalleloperationoftransformer.(2)Noloadtaprangesshouldbeselectedtoprovideanadequatelow-sidebusvoltage.(3)Ifthehigh-sideorlow-sidevoltagesvaryoverawiderangeduringtheloadcycle,itmaybenecessarytoprovidebusregulation.Theactualregulationcan

8、becalculatedusingthesystemandloadcharacteristics.Ifregulatingequipmentisneeded,itmaybedesirabletoprovideitinthetransformerbyusingloadtapchanger(LTC)equipment.Iftheneedforbusregulationisnotpresentlyevident,butmayberequiredi