已阅读5页,还剩5页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
SpeedControlofDCMotorRegulatorSystemsAregulatorsystemisonewhichnormallyprovidesoutputpowerinitssteady-stateoperation.Forexample,amotorspeedregulatormaintainsthemotorspeedataconstantvaluedespitevariationsinloadtorque.Eveniftheloadtorqueisremoved,themotormustprovidesufficienttorquetoovercometheviscousfrictioneffectofthebearings.Otherformsofregulatoralsoprovideoutputpower;Atemperatureregulatormustmaintainthetemperatureof,say,anovenconstantdespitetheheatlossintheoven.Avoltageregulatormustalsomaintainmustoutputvoltageconstantdespitevariationintheloadcurrent.Foranysystemtoprovideanoutput,e.g.,speed,temperature,voltage,etc,anerrorsignalmustexistundersteady-stateconditions.ElectricalBrakingInmanyspeedcontrolsystem,e.g.,rollingmillsminewinders,etc.,theloadhastobefrequentlybroughttoastandstillandreversed.Therateatwhichthespeedreducesfollowingareducedspeeddemandisdependentonthestoredenergyandthebrakingsystemused.Asmallspeedcontrolsystem(sometimesknownasavelodyne)canemploymechanicalbraking,butthisisnotfeasiblewithlargespeedcontrollerssinceitisdifficultandcostlytoremovetheheatgenerated.Thevariousmethodsofelectricalbrakingavaiableare:(1)Regenerativebraking.(2)Eddycurrentbraking.(3)Dynamicbraking.(4)Reversecurrentbraking(plugging).Regenerativebrakingisthebestmethod,thoughnotnecessarilythemosteconomic.Thestoredenergyintheloadisconvertedintoelectricalenergybytheworkmotor(actingtemporarilyasagenerator)andisreturnedtothepowersupplysystem.Thesupplysystemthusactsasa“sink”intowhichtheunwantedenergyisdelivered.Providingthesupplysystemhasadequatecapacity,theconsequentriseinterminalvoltagewillbesmallduringtheshortperiodsofregeneration.IntheWard-LeonardmethodofspeedcontrolofDCmotors,regenerativebrakingisinherent,butthyristordriveshavetobearrangedtoinverttoregenerate.Inductionmotordrivercanregenerateiftherotorshaftisdrivenfasterthanspeedoftherotatingfield.Theadventoflow-costvariablevariable-frequencysuppliesfromthyristorinvertershavebroughtaboutconsiderablechargesintheuseofinductionmotorsinvariablespeeddrives.Eddycurrentbrakingcanbeappliedtoanymachine,simplybymountingacopperoraluminiumdiscontheshaftandrotatingitinamagneticfield.Theproblemofremovingtheheatgeneratedissevereinlargesystemasthetemperatureoftheshaft,bearing,andmotorwillberaisedifprolongedbrakingisapplied.Indynamicbreaking,thestoredenergyisaresistorinthecircuit.WhenappliedtosmallDCmachines,thearmaturesupplyisdisconnectedandaresistorisconnectedacrossthearmature(usuallybyarelay,contactor,orthyristor).Thefieldvoltageismaintained,andbrakingisapplieddowntothelowestspeed.Inductionmotorsrequireasomewhatmorecomplexarrangement,thestatorwindingsbeingdisconnectedfromtheACsupplyandreconnectedtoaDCsupply.Theelectricalenergygeneratedisthendissipatedintherotorcircuit.DynamicbrakingisappliedtomanylargeAChoistsystemwherethebrakingdutyisbothsevereandprolonged.Anyelectricalmotorcanbebroughttoastandstillbysuddenlyreconnectingthesupplytoreversethedirectionofrotation(reversecurrentbraking).Appliedundercontrolledconditions,thismethodofbrakingissatisfactoryforalldrivers.Itsmajordisadvantageisthattheelectricalenergyconsumedbythemachinewhenbrakingisequaltothestoredenergyintheload.Thisincreasestherunningcostsignificantlyinlargedrives.EqualpulsewidthPWMlawVVVF(VariableVoltageVariableFrequency)installsintheearlytimeisusesPAM(PulseAmplitudeModulation)tocontrol,itsinventorpartwhichthetechnologyrealizesbutonlycanoutputthefrequencyadjustablesquare-wavevoltagenottobeabletoadjustthepressure.ThepulsewidthPWMlawarepreciselyinordertoovercome,isinthePWMlawwhichthePAMlawthisshortcomingdevelopmentcomesthesimplestonekind.ItiseachpulsewidthequalpulserowtookthePWMwave,throughachangepulserowcyclemaythefrequencymodulation,thechangepulsewidthorthedutyfactormayadjustthepressure,usesthesuitablecontrolmethodthentocausethevoltageandthefrequencycoordinationchange.IsoppositeinthePAMlaw,thismethodmeritsimplifiedtheelectriccircuitstructure,enhancedtheinputendpowerfactor,butsimultaneouslyalsohasintheoutputvoltagebesidesthefundamentalwave,butalsocontainsthebigharmoniccomponent.StochasticPWMThattimethehighefficiencytransistormainlyforthebipolarityDaringtontriode,thecarrierfrequencygenerallydidnotsurpass5kHz,thevibrationwhichtheelectricalmachinerywindingelectromagnetismnoiseandtheovertonecreatedhasarousedpeoplesinterest.Inordertoobtaintheimprovement,thestochasticPWMmethodarisesatthehistoricmoment.Itsprincipleisthestochasticchangeturn-onfrequencycausestheelectricalmachineryelectromagnetismnoisetobelimitedtoapproximatelythebeltwhitenoise(inlinearfrequencycoordinatesystem,variousfrequenciesenergydistributioniseven),althoughthenoiseadecibelnumberhasnotalwayschanged,butweakensgreatlytakethefixedturn-onfrequencyasthecharacteristiccolorednoiseintensity.Becauseofthis,evenifinIGBTbywidespreadapplicationtoday,hashadtolimitregardingthecarrierfrequencyiscomparingthelowfrequencythesituation,stochasticPWMstillhaditsspecialvalue;Ontheotherhandexplainedeliminatesthemachineryandtheelectromagnetismnoisebestmethodenhancestheoperatingfrequencyblindly,thestochasticPWMtechnologywaspreciselyprovidesananalysis,hassolvedthiskindofquestionbrand-newmentality.SpatialvoltagevectorcontrolPWMSpatialvoltagevectorcontrolPWM(SVPWM)alsocallsthemagneticfluxsinePWMlaw.Ittakethethree-phaseprofilewholeproductioneffectasthepremise,takeapproachestheelectricalmachineryairgaptheidealcircularrotaryfieldpathasthegoal,hastheactualmagneticfluxwiththeinventordifferentswitchpatterntoapproachthebasedirectorcirclemagneticflux,bytheirscomparisonresultdecidedtheinventortheswitch,formsthePWMprofile.Thislawembarksfromtheelectricmotorangle,regardsastheinventorandtheelectricalmachineryawhole,inscribesthepolygontoapproachthecirclethewaytocarryonthecontrol,causestheelectricalmachinerytoobtainthepeak-to-peakvalueconstantcircularmagneticfield(sinemagneticflux).Theconcretemethoddividesintothemagneticfluxsplit-ringtypeandthemagneticfluxclosedlooptype.Themagneticfluxsplit-ringlawsynthesizesanequivalentvoltagevectorwithatwonon-vanishingvectorsumnullvector,ifthesamplingtimeenoughissmall,maysynthesizetherandomvoltagevector.Whenthislawoutputratio-voltagesine-wavemodulationenhances15%close,sumoftheharmoniccurrenteffectivevaluesmallest.Themagneticfluxclosedlooptypeintroducesthemagneticfluxfeedback,controlsthemagneticfluxthesizeandthechangespeed.Estimatesthemagneticfluxafterthecomparisonandassignsthemagneticflux,accordingtotheerrordecidedhasthenextvoltagevector,formsthePWMprofile.Thismethodhasovercomethemagneticfluxsplit-ringmethodinsufficiency,whenhassolvedtheelectricalmachinerylowspeed,thestatorresistanceaffectsthemajorproblem,reducedtheelectricalmachinerypulsationandthenoise.Butbecausehasnotintroducedthetorquetheadjustment,thesystemperformancehasnothadthefundamentalimprovement.VectorControlPWMThevectorcontrolalsocalledthemagneticfielddirectiondetectioncontrol,itsprincipleisasynchronousmotorunderthree-phasecoordinatesystemstatorcurrentIa,IbandIc,throughthethree-phase/twophasetransformation,equivalentbecomesundertwostaticcoordinatesystemsalternatingcurrentIa1andIb1,againthroughpressestherotormagneticfielddirectiondetectionrevolvingtransformation,equivalentbecomesunderthesynchronizedrevolvingcoordinatesystemdirectcurrentIm1andIt1(Im1isequaltothedirectcurrentmotorexcitingcurrent;It1isequaltothearmatureelectriccurrentwhichisproportionalwiththetorque),thentheimitationdirectdischargemotivecontrolmethod,realizestothemotorcontrol.Itsessenceisthemotorequivalentisthedirectcurrentmotor,separatelytothespeed,themagneticfieldtwocomponentscarriesontheindependentcontrol.Throughth
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 高考政治复习专题一生活与消费市赛课公开课一等奖省名师获奖课件
- 中考政治教材知识梳理七上课时2生活中有你()教案省公开课一等奖百校联赛赛课微课获奖课件
- 幼儿园园长任职培训班结业典礼发言
- 第一节-金属的化学性质省公开课金奖全国赛课一等奖微课获奖课件
- 湖北洪湖市瞿家湾中学2023-2024学年中考试题猜想英语试卷含答案
- 职业道德与法律第一课新市公开课一等奖省赛课微课金奖课件
- 黑龙江省松北区2024届中考语文四模试卷含解析
- 高考英语复习-第一部分-Module-4-Which-English市赛课公开课一等奖省名师获
- 高考数学复习第八章解析几何第九节圆锥曲线的综合问题理市赛课公开课一等奖省名师获奖课件
- 高考数学复习第四章平面向量数系的扩充与复数的引入第3讲平面向量的数量积及应用举例文市赛课公开课一等奖
- 员工信息保护与隐私管理制度
- 2025届高考英语三轮冲刺 语法填空 复习课件
- 学年福建厦门大学嘉庚学院体育教学部专任教师招聘笔试真题2023
- 小学语文六年级下册第三单元作业设计
- 文言文二则囊萤夜读(课件)语文四年级下册
- 公共关系的历史与发展讲义课件(ppt 68页).ppt
- 《尚书》.ppt
- 仙居针刺无骨花灯.ppt
- 十岁成长礼诗朗诵
- 给水工程第15和16章作业答案
- 三极管(完整)ppt课件
评论
0/150
提交评论