电气毕业设计外文翻译

本科毕业设计外文文献及译文文献、资料题目：《SpecialEnglishforArchitecturalElectricEngineeringandAutomation》文献、资料来源：期刊（著作、网络等）文献、资料发表（出版）日期：2006.4院（部）：信息与电气工程学院学院专业：电气工程与自动化班级：电气093姓名：孙德艺学号：2009081102指导教师：陈红艳翻译日期：2013.6.30山东建筑大学毕业设计外文文献及翻译外文文献一：TransformerOneofthemostvaluableapparatusinelectricpowersystemisthetransformer,foritenablesustoutilizedifferentvoltagelevelsacrossthesystemforthemosteconomicalvalue.Generationofpoweratthesynchronousmachinelevelisnormallyatarelativelylowvoltage，whichismostdesirableeconomically．Steppingupofthisgeneratedvoltagetohighvoltage，extra-highvoltageoreventoultra-highvoltageisdonethroughpowertransformerstosuitthepowertransmissionrequirementtominimizelossesandincreasethetransmissioncapacityofthelines．Thistransmissionvoltagelevelisthensteppeddowninmanystagesfordistributionandutilizationpurposes．Atransformerisastaticdevicefortransferringelectricenergyfromonecircuittoanotherelectromagnetically，thatis，byinductioninsteadofbyconduction．Itsusualfunctionistotransferenergybetweencircuitsofdifferentvoltage．Atransformerhasamagneticcoreonwhichtherearetwoormorewindings．Thesewindingsareinsulatedfromeachotherandfromground．Inautotransformers，however，thewindingsareconnectedtogether．Theassemblyofcoreandcoilsisnormallyinsulatedandcooledbyimmersioninmineraloilorothersuitableliquidwithinanenclosingtank．Connectiontothewindingsisbymeansofinsulatingbushings，usuallythroughthecover.The“ratiooftransformation”isdeterminedbytherelativenumberofturnsineachofhewindings．Thisisknownasthe“turnratio”anditistheratiooftheno-loadvoltages．Whentheunitiscarryingload,theratiooftheactualvoltagesisslightlydifferentbecauseofthedropcausedbytheflowof1oadcurrentthroughtheimpedanceofthetransformerwindings．Atratedload,thisdropisknownasthevoltageregulation.Theamountofvoltagedropvarieswiththepowerfactoroftheoutputevenwhenthekilovolt-amperesremainconstant．Practicallyallpowertransformersandmanydistributiontransformershavetapsinoneormorewindingsforchangingtheturnratio．Changingtheratioisdesirable山东建筑大学毕业设计外文文献及翻译fortworeasonstocompensateforvaryingvoltagedropinthesystemandtoassurethatthetransformeroperatesasnearlyaspossibleatthecorrectcoredensity．Forthelatterpurpose,thetapsshouldbeinthewindingsubjecttothevoltagevariation.De-energizedtapchangersareusedwhenitisexpectedthattheratiowillneedtobechangedonlyinfrequently,becauseofloadgrowthorsomeseasonalchange．Thedesiredtapisselectedbymeansofaratioadjuster(noloadtaps)．Loadtapchanger(LTC)isusedwhenchangesinratiomaybefrequentorwhenitisundesirabletode-energizethetransformertochangeatap．Itseldommakesmuchdifferencetotheuserwhichwindingorwindingsaretapped；therefore，thechoiceisusuallymadebythedesigneronthebasisofcostandgooddesign.BothwindingcurrentandvoltagemustbeconsideredwhenapplyingLTCequipment．HighvoltageandhighcurrentapplicationsrequirespecialconsiderationstoarriveatanoptimumlocationfortheLTCequipment．StepdownunitsusuallyhaveLTCinthelow-voltagewindingandde-energizedtapsinthehighvoltagewinding．Whenenergyistobetransferredbetweentwocircuitsofnearlythesamevoltage．Theuseofautotransformersaffordscostsavingsovertwo-windingunits．Thenearerthevoltagesaretoeachother,thesmallerwillbetheautotransformerperkilovolt-ampereofoutput，andthegreaterthesavings．Thesimplicityofphasingoutsystemshasincreaseditsuse．MostautotransformersareY-connected，andithasbeenastandardAmericanpracticetoaddalowcapacity,deltawinding．Thisisfrequentlyreferredtoasa“deltatertiary“．Itsprimarypurposehasbeentoprovideaninternalpathforthethirdharmoniccurrents(requiredforexcitation)，thusreducingthosecurrentsonthepowersystem．Italsohelpstostabilizetheneutralandtogroundthesystembetter．Inrecentyears，theuseofshieldedtelephonecablehasreducedtherequirementsforthedeltatertiary.Becauseanautotransformerdoesnotaffordelectricalseparationbetweenthetwocircuits,disturbancesoriginatingononecircuitcanbecommunicatedtotheother．Thisdifficultyisminimizedbysolidlygroundingtheneutraloftheautotransformer.Solidlygroundingtheneutral，however,causes(amongotherthings)currentofshort-circuitmagnitudetoflowthroughthedelta-connectedtertiarywindingduringgroundfaultsoneithersystem.山东建筑大学毕业设计外文文献及翻译Autotransformersarenotinherentlyself-protectingand,therefore，allwindingsmustbeexaminedformechanicalstrengthasappliedtothesystemwheretheywillbeused.Tertiariesarenormally35％ofthephysicalsizeofthelargestwindingoftheautotransformer,unlessotherwisespecifiedbytheuser.Thebulkofa11transformers，exceptforlargeextra-highvoltage(EHV)anddistributionunitsarethree-phaseunits．Intheearlydaysoftheindustry，ItwasalmostuniversalpracticeintheUnitedStatestousethreesingle-phaseunitsconnectedinathree-phasebank．InsulationclearancesandshippinglimitationsforcertainlargeEHVunitsnowrequirethisdesign．Thedistributionsystemsservemainlysingle-phaseloadsinresidentialareasandareservedfromsingle-phasetransformers．中文译文一：变压器在电力系统中最有价值的一个装置是变压器,因为它使我们能够在系统中利用不同的电压水平获得最经济的价值。同步电机的发电电压水平通常是在一个相对较低的电压,这是最令人满意也是最经济的。把发电电压升高到高电压,超高压甚至超高电压是通过电源变压器实现的,这样可以适应电力传输要求,减少电压损失,提高线路的传输容量。在不同的阶段，我们可以根据配电和使用目的的要求把高电压通过变压器降到低电压。一个变压器是一个静态装置，因为电能量从一个电路转移到另一个电路是通过电磁的形式实现的