电气工程及其自动化专业英语翻译

Semiconductorswitchesareveryimportantandcrucialcomponentsinpowerelectronicswitchesaremeanttobethesubstitutionsofthemechanicalswitches,buttheyareseverelylimitedbythepropertiesofthesemiconductormaterialsandprocessofmanufacturing.在电力电子系统，中半导体开关是非常重要和关键部件。半导体开关将要替换机械开关,但半导体 材料 关于××同志的政审材料调查表环保先进个人材料国家普通话测试材料农民专业合作社注销四查四问剖析材料 的性质和生产过程严重限制了他们。Switchinglosses开关损耗PowerlossesinthepowereletronicconvertersarecomprisedoftheSwitchinglossesandparasiticlosses.电力电子转换器的功率损耗分为开关损耗和寄生损耗theparasiticlossesaccountforthelossesduetothewindingresistancesoftheinductorsandtransformers,thedielectriclossesofcapacitors,theeddyandthehysteresislosses.寄生损失的绕组电感器、变压器的阻力、介电损耗的电容器,涡流和磁滞损耗theswitchinglossesaresignificantandcanbemanaged.这个开关损耗是非常重要的,可以被处理。theycanbefurtherdividedintothreecomponents:(a)theon-statelosses,(b)theoff-statelossesandthelossesinthetransitionstates.他们可以分为三个部分:通态损耗，断态损耗和转换过程中产生的损耗。On-StateLosses通态损耗：Theelectricalswitchesconductheavycurrentandhavenonzerovoltageacrosstheswitchintheon-statepowerlossesaregivenbyPon=Usonif.这个电子开关能导通大电流，并且在通态时有非零的压降。这个通态功率损耗的公式为Pon=Usonif.TheUsonandIfarerespectivelytheswitchvoltageintheon-stateandtheforwardcurrentthroughtheexample,thetypicalpowerdiodesandthepowertransistorshavenearlytolvoltacrossthemintheforwardcurrentscanbehundredstothousandsofon-statepowerlossesareverysignificant.其中Uson是通态时开关上的压降，if是流过开关的电流。例如，典型的功率二极管和功率晶体管有近似~1伏的通态压降。而电流会有数百到数千安培。这个通态损耗非常重要。Off-StateLosses断态损耗Theelectricalswitcheswithstandhighvoltagesandhavenonzeroleakagecurrentthroughtheswitchintheoff-statepowerlessesaregivenbyPoh=Uoffir在关断状态时，电子开关到经受得起高电压，并会有非零的漏电流。断态损耗的公式为Poh=Uoffir.TheUsoffandIrarerespectivelythereversebiasvoltageintheoff-stateandthereversecurrentthroughtheexample,thetypicalpowerdiodesandthepowertransistorshavehighreversevoltagesinhundredstothousandsofvoltsandmicroampstomilliampsthroughthemintheoffstate.其中Uoff在断态时的反向偏置电压，ir是流过开关的反向漏电流。例如，典型的功率二极管和功率晶体管有很高的反向压降几百到几千伏和几微安到几毫安的漏电流。Transition-StateLosses转换损耗：Thepracticalswitchingdeviceshavelimitedcapabilitiesofrateofvoltagetransitionandtherateofcurrentnonabrupttransitionratesgiverisetopowerlossesintheswitchingwillexaminetheseswitchinglossesintwocasesseparately:theinductiveandcapacitiveloads.在实际的开关装置限制了电压变换率和电流变化率。非突变引起了开关装置的功率损耗。我们测试开关损耗时分两种情况：感性负载和容性负载。SwitchingwithInductiveLoad接感性负载的开关：Theindutorisassumedtobelargesothatthecurrentthroughitinsteadystateisnearlyconstantthatinitiallytheswitchisinductorcurrentis+Ioandfreewheelsthroughdiodetheswitchisturnedon,thecurrentthroughtheswitchbeginstobuilduplinearly(anassumption)to+IowhilethediodeV1isstillondiodehaszerovoltageacrossit(anidealdiode),hence,thevoltageontheswitchisheldconstantat+thecurrentbuildupisover,thediodeV1ceasestoconductandthevoltageontheswitchrampslinearly(againanassumption)downtozero.假设电感无穷大，即在稳定时流经电感的电流是恒定的Io，假定开始时开关处于关断状态。电感电流为+Io惯性流过二极管V1。当开关闭合后，电流流经开关开始建立线性上升+Io此时二极管扔导通。二极管压降为0，此时开关两端电压维持在+Us当电流建立完成后，二极管V1截止，开关两端电压线性下降为0。Whentheswitchisturnedoff,thevoltagebeginstobuilduplinearlyto+uswhilethediodeV1isoff.whilethediodeisoffthecurrentthroughtheswitchequalstheinductorcurrent,whichisconstantI0Aftertheswitchvoltagereachesaero,thecurrentthroughtheswitchbeginstodecreasebelowI0,astheremainingcurrentisnowsteeredthroughthediodeV1whichhasnowturnedonThecurrentthroughtheswithchrampsdowntozeroultimately.Switchingwaveformswithinductiveloadareshownin开关打开后，开关两端电压线性上升至Us。此时二极管仍截止，二极管截止，流过开关的电流相当于流过电感的电流，维持在恒定的Io。开关电压到0时，通过开关的电流开始上升到Io以下。此时余留的电流正转向二极管V1，V1导通。最终通过开关的电流下降到0，开关过程的波形的电感负载波形见图3-1Theswitchinglossesaregivenby:Psw=1/2UsIo[……….]fs开关损耗的公式是Psw=1/2UsIo[……….]fsTheswitchingpowerlossesincreaselinearlywiththeswitchingrequencylikeintheresistivecasebutaboutsixtimesmore.Theupperboundontheswitchingfrequencyisalsoabouthalf.开关功率损耗线性增加随着开关频率此时的损耗要比阻性负载损耗的6倍还多。当f取最大时Psw=1/2UsIo。SwitchingwithcapacitiveLoad开关接有容性负载Thecapacitorisassumedtobelargesothatthevoltagethroughisinstedystateisnearlyconstantthatinitiallytheswitchison,hence,thecuttentthroughtheswitchiscapacitorvoltageisUthevoltageacrosstheswitchiszeroandthediodeV1isreversetheswitchisturnedoff,theswitchvoltagebeginstorampupto+U0whilethediodeV1isstillthisbuildup,thecurrentthroughtheswitchisheldconstantatthevoltagebuildupisover,thediodeV1beginstoconductandthevoltageontheswitchisclampedatU0,andthecurrentthroughtheswitchrampslinearly(againanassumption)downtozero.假设电容器很大，致使在稳定状态下其两端电压接近为常数Uo。假使开关初始状态为闭合，则通过开关的电流为Is。电容器的电压为Uo开关两端的电压为零，二极管V1反向偏置。当开关打开后，开关两端电压开始上升到Uo，此时二极管一直关断。当电压等于Uo时，二极管V1开始导通并且开关两端电压被钳位在Uo。流过开关的电流线性下降到零。Whentheswitchisclosed,thecurrentbeginstobuilduplinearlytoIswhilethediodeV1isstillon.ThevoltageontheswitchremainsclampedattheswitchcurrentreachesIs,thediodeturnsoffandthevoltageontheswitchbeginstorampdowntozero.当开关闭合，电流开始上升至Is，此时V1仍然导通，开关两端电位被钳位在Uo。当开关电流等于Is时，二极管关断并且开关两端电压线性下降至0。Theswitchingpowerlossesinthecaseofcapacitiveloadalsohavesimilardependenceasinthecaseofinductiveloads.当开关闭合，电流开始上升至Is，此时V1仍然导通，开关两端电位被钳位在Uo。当开关电流等于Is时，二极管关断并且开关两端电压线性下降至0。Theswitchingpowerlossesinthecaseofcapacitiveloadalsohavesimilardependenceasinthecaseofinductiveloads.接容性负载情况下的开关功率损耗的决定因素与感性负载情况下有相似之处。Theswitchinglossescanbeusuallyminimizedintwoways;1diverttheenergyfromtheswitchtoalossornon-losscircuitor2switchateitherzerocurrentoratzerofirstiscalledsnubberingandthelaterisknownaszero-voltageandzero-currentswithching.开关损耗一般被归为两点：1。开关的能量转化成了损耗或无损耗电流或开关的过0电流或过0电压，第一个被称为缓冲，最后一个被成为过0电流或过0电压的开关。