中英文翻译--直流电机脉冲宽度调制.doc

PWM直流电机脉冲宽度调制(PulseWidthModwtated-简称PWM)调速系统产生于70年代中期.最早用于不可逆、小功率驱动,例如自动跟踪天文望远镜、自动记录仪表等。近十多年来,由于晶体管器件水平的提高及电路技术的发展,同时又因出现了宽调速永磁直流电机,它们之间的结合促使PWM技术的高速发展,并使电气驱动技术推进到一个新的高度.在国外,PWM最早是在军事工业以及空间技术中应用。它以优越的性能,满足那些高速度、高精度随动跟踪系统的需求。近八、九年来,进一步扩散到民用工业,特别是在机床行业、自动生产线及机器人等领域中广泛应用。可以这样说,六十年代中期发展起来的晶体管OTL电路、OCL电路,特别是桥型无变压器输出的BTL电路,为PWM系统的发展奠定了电路基础,而各种先进的功率器件(如GTR,IGBT模块等)及宽调速直流电机的出现,更为PWM技术的应用提供了良好的条件。PWM系统的特点1)开关损耗小,变流器效率高。2)系统主回路电源是经过整流及大容量电容器虑波后供电,因而不会因电网电压波形的失真而影响调节质量。3)以1KHZ-8KHZ的高频脉冲电流给电机的电枢供电,由于是感性负载,脉冲电流得以滤平,所以波系数小,电机发热量小,可以减小机械变形,从而能提高工作机械的精度。也正是由于波形系数小,电机利用率高,从相同发热量的角度考虑,PWM系统获得可以比SCR系统高1.3-1.8倍的转矩,因此PWM系统可以选用较小容量的电机.特别是工作在正反转频繁的伺服系统中,其优点尤为突出。4)系统的响应频带很宽,可达到100-200HZ以上。因此起制动非常快,而且超调量小,可以大大提高高冲击率机械的生产效率。5)因系统采样频率高,频带宽,所以抗负载扰动的性能好,动态速度下降小,恢复时间快,因此动态硬度好,加工零件表面光洁度高。6)同样由于采样频率高,避开了电机及传动机械的共振点,所以运动平稳,这也是提高加工光洁度的一个有利因素。7)PWM系统很容易地实现四象限运行。当用于2千瓦以下的电机时,在再生制动的情况下,再生的能量可储存在功率电容器中,2千瓦以上的电机,再采用特殊电子线路,让能量馈送到再生负载电阻上去,以加快制动过程,并防止电子元件因过压而造成损坏。8)PWM系统调速范围宽,最低速度可达到1转/24小时。这特别适用于自动记录系统。例如地震监测站的地磁变化曲线的记录等。而在机床伺服驱动系统中应用时,1转/分钟即够用。PWM系统的最低速度实际取决于速度调节器的零点飘移量、速度给定电压的精度与分辩率、以及测速电机的纹波系数和电动机的波动力矩等。从PWM伺服单元本身看,其潜力是很大的。9)有于PWM本身性能的优越,因此不必象SCR系统那样,为了提高系统性能而费尽心机,添加了许多环节,增加了系统的复杂性。例如各种滤波环节、电抗器之类的惯性环节、电流自适应环节以及函数发生器环节等等。使驱动系统的结构更加简单可靠,调整于维护都十分方便。同时对个种参数不同的直流电机均有很好的适应性。PWMThedirectcurrentmachinepulsewidthmodulation(PulseWidthModwtated-iscalledPWM)tomodulatevelocitythesystemtoproduceinthe70sintermediatestagesUsesinmostearlyirreversiblily,thelowpoweractuation,Forexampleautomatictrackingtrackingtelescope,self-registeringinstrumentandsoon.Nearlymorethantenforyears,Asaresultoftransistorcomponentlevelenhancementandelectriccircuittechnologydevelopment,Atthesametimeandfurtherbecauseappearedthewidthvelocitymodulationpermanentmagnetismdirectcurrentmachine,BetweenthemtheunionurgesthePWMtechnologythehighspeeddevelopment,AndcausestheelectricalactuationtechnologytoadvancenewlytohighlyInoverseas,PWMismostearlyappliesinwarindustryaswellasthespatialtechnology.Itbysuperiorperformance,Satisfiesthesehighvelocity,thehighaccuracyfollow-uptrackingsystemdemand.Nearlyeight,fornineyears,Furtherproliferatestotheconsumerindustry,Speciallyindomainandsooninenginebedprofession,automaticproductionlineandrobotwidespreadapplication.Maysaylikethis,The60sintermediatestagesdeveloptransistorOTLelectriccircuit,OCLelectriccircuit,SpeciallythebridgenochangedepressoroutputsBTLelectriccircuit,HaslaidtheelectriccircuitfoundationforthePWMsystemdevelopment,Buteachkindofadvancedpowercomponent(forexampleGTR,IGBTmoduleandsoon)andwidthvelocitymodulationdirectcurrentmachineappearance,MorethePWMtechnologyapplicationhasprovidedthegoodcondition.PWMsystemcharacteristic1)theswitchlosesslightly,Theconverterefficiencyishigh.2)thesystematichostringcurrentispondersthewaveaftertherectificationandthelargecapacitycapacitortosupplypower,Thuscannotbutaffecttheadjustmentqualitybecauseoftheelectricalnetworkvoltagewaveformdistortion.3)givestheelectricalmachinerybythe1KHZ-8KHZhighfrequencypulseelectriccurrentthearmaturepowersupply,Becauseistheperceptualload,Thepulseelectriccurrentcanfilterevenly,Thereforethewavecoefficientissmall,Theelectricalmachinerycalorificcapacityissmall,Mayreducethemachinerydistortion,Thuscanenhancetheworkmachinerytheprecision.Alsoispreciselybecausethewaveformfactorissmall,Theelectricalmachineryusefactorishigh,Consideredfromthesamecalorificcapacityangle,ThePWMsystemobtainsmaySCRsystembehigherthan1.3-1.8timeoftorque,ThereforethePWMsystemmayselectthelow-powerelectricalmachinerySpeciallyworksinisreversinginthefrequentservosystem,Itsmeritoutstandingly.4)thesystemresponsefrequencybandisverywide,Mayachieveabove100-200HZ.Thereforegetsupappliesthebrakeextremelyquickly,Moreoveroverissmall,Mayenhancethehighimpactratemachinerygreatlytheproductionefficiency.5)becausethesystemsamplingfrequencyishigh,Bandwidth,Thereforetheanti-loadperturbationperformanceisgood,Thedynamicspeeddropsslightly,Restoresthetimetobequick,Thereforethedynamicdegreeofhardnessisgood,Processingcomponentssuperficiallyattractivefinenessishigh.6)similarlybecausethesamplingfrequencyishigh,Hasavoidedtheelectricalmachineryandthegearingresonancepoint,Thereforethemovementissteady,Thisalsoisenhancestheprocessingsmoothfinishafavorablefactor.7)thePWMsystemveryeasilyrealizesfourquadrantsmovements.Whenusesin2kilowattbelowelectricalmachinery,Inelectricregenerativebrakingsituation,Theregenerationenergymaystoreupinthepowercapacitor,2kilowattaboveelectricalmachinery,Againusesthespecialelectroniccircuit,Lettheenergypresenttotheregenerationloadresistancecomesup,Byspeedsupappliesthebraketheprocess,Andpreventstheelectroniccomponentbecausetopressbutcreatesthedamage.8)thePWMsystemvelocitymodulationscopeiswide,Minimumspeedmayamounttofor1revolutionof/24hour.Thisissuitablespeciallyfortheautomaticrecordingsystem.Forexampleearthquakeinspectionstationmagneticvariationcurverecordandsoon.Butwhenenginebedservodrivesystemsdsapplication,1revolutions/Theminutenamelyissufficient.PWMsystemminimumspeedisdecidedactuallyinthespeedregulatorzerospotdriftsthequantity,thespeedassignsthevoltagetheprecisionwithdistinguishingrate,aswellasmeasuresthefastelectricalmachinerytheripplecoefficientandtheelectricmotorundulationmomentofforceandsoon.LookedfromPWMservounititself,Itspotentialisverybig.9)hasinPWMitselfperformancesuperior,ThereforedoesnotneedtolooklikeSCRsystemsuch,Forenhancethesystemperformancebuttothinkofeverymeans,Increasedmanylinks,Increasedthesystemcomplexity.Forexampleeachkindoffilterlink,reac