PWM直流電機脈沖寬度調(diào)制(PulseWidthModwtated-簡稱PWM)調(diào)速系統(tǒng)產(chǎn)生于70年代中期.最早用于不可逆、小功率驅(qū)動,例如自動跟蹤天文望遠鏡、自動記錄儀表等。近十多年來,由于晶體管器件水平的提高及電路技術(shù)的發(fā)展,同時又因出現(xiàn)了寬調(diào)速永磁直流電機,它們之間的結(jié)合促使PWM技術(shù)的高速發(fā)展,并使電氣驅(qū)動技術(shù)推進到一個新的高度.在國外,PWM最早是在軍事工業(yè)以及空間技術(shù)中應(yīng)用。它以優(yōu)越的性能,滿足那些高速度、高精度隨動跟蹤系統(tǒng)的需求。近八、九年來,進一步擴散到民用工業(yè),特別是在機床行業(yè)、自動生產(chǎn)線及機器人等領(lǐng)域中廣泛應(yīng)用?？梢赃@樣說,六十年代中期發(fā)展起來的晶體管OTL電路、OCL電路,特別是橋型無變壓器輸出的BTL電路,為PWM系統(tǒng)的發(fā)展奠定了電路基礎(chǔ),而各種先進的功率器件(如GTR,IGBT模塊等)及寬調(diào)速直流電機的出現(xiàn),更為PWM技術(shù)的應(yīng)用提供了良好的條件。PWM系統(tǒng)的特點1)開關(guān)損耗小,變流器效率高。2)系統(tǒng)主回路電源是經(jīng)過整流及大容量電容器慮波后供電,因而不會因電網(wǎng)電壓波形的失真而影響調(diào)節(jié)質(zhì)量。3)以1KHZ-8KHZ的高頻脈沖電流給電機的電樞供電,由于是感性負載,脈沖電流得以濾平,所以波系數(shù)小,電機發(fā)熱量小,可以減小機械變形,從而能提高工作機械的精度。也正是由于波形系數(shù)小,電機利用率高,從相同發(fā)熱量的角度考慮,PWM系統(tǒng)獲得可以比SCR系統(tǒng)高1.3-1.8倍的轉(zhuǎn)矩,因此PWM系統(tǒng)可以選用較小容量的電機.特別是工作在正反轉(zhuǎn)頻繁的伺服系統(tǒng)中,其優(yōu)點尤為突出。4)系統(tǒng)的響應(yīng)頻帶很寬,可達到100-200HZ以上。因此起制動非?？?而且超調(diào)量小,可以大大提高高沖擊率機械的生產(chǎn)效率。5)因系統(tǒng)采樣頻率高,頻帶寬,所以抗負載擾動的性能好,動態(tài)速度下降小,恢復(fù)時間快,因此動態(tài)硬度好,加工零件表面光潔度高。6)同樣由于采樣頻率高,避開了電機及傳動機械的共振點,所以運動平穩(wěn),這也是提高加工光潔度的一個有利因素。7)PWM系統(tǒng)很容易地實現(xiàn)四象限運行。當用于2千瓦以下的電機時,在再生制動的情況下,再生的能量可儲存在功率電容器中,2千瓦以上的電機,再采用特殊電子線路,讓能量饋送到再生負載電阻上去,以加快制動過程,并防止電子元件因過壓而造成損壞。8)PWM系統(tǒng)調(diào)速范圍寬,最低速度可達到1轉(zhuǎn)/24小時。這特別適用于自動記錄系統(tǒng)。例如地震監(jiān)測站的地磁變化曲線的記錄等。而在機床伺服驅(qū)動系統(tǒng)中應(yīng)用時,1轉(zhuǎn)/分鐘即夠用。PWM系統(tǒng)的最低速度實際取決于速度調(diào)節(jié)器的零點飄移量、速度給定電壓的精度與分辯率、以及測速電機的紋波系數(shù)和電動機的波動力矩等。從PWM伺服單元本身看,其潛力是很大的。9)有于PWM本身性能的優(yōu)越,因此不必象SCR系統(tǒng)那樣,為了提高系統(tǒng)性能而費盡心機,添加了許多環(huán)節(jié),增加了系統(tǒng)的復(fù)雜性。例如各種濾波環(huán)節(jié)、電抗器之類的慣性環(huán)節(jié)、電流自適應(yīng)環(huán)節(jié)以及函數(shù)發(fā)生器環(huán)節(jié)等等。使驅(qū)動系統(tǒng)的結(jié)構(gòu)更加簡單可靠,調(diào)整于維護都十分方便。同時對個種參數(shù)不同的直流電機均有很好的適應(yīng)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