直流电机原理ppt课件.ppt

MotorStartTheory 电机起动原理 T 2005 11001MST LowSlipvFullSlip低滑移与满滑移 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT Amotor sstartperformancecharacteristicssetthelimitsofwhatcanbeachievedwitheitherafullvoltageorreducedvoltagestarter 电机起动性能规定使用全电压起动器或降压起动器能达到的极限值 Itisespeciallyimportanttoconsidermotorstartcharacteristicswhenseekingto MinimisestartcurrentMaximisestarttorque当尝试以下方式时考虑电机起动特性尤其重要 将起动电流降至最小 将起动扭矩增至最大 MotorPerformance电机性能 Rotordesignaffectsstartingperformance 转子的设计影响起动性能 Statordesignaffectsfullspeedperformance 定子的设计影响全速性能 Theshape positionandmaterialoftherotorbarsaffectthecurrentdrawnandtorqueproducedduringmotorstarting 转子杆的形状 位置和材料影响引入电流和电机起动时产生的扭矩 MotorPerformance电机性能 Amotor sstartperformancecanbeidentifiedbyexaminingthemotordatasheet 电机起动性能可通过检查电机数据表得到确认 Thetabledetailsselectedperformancedataforarangeof110kWmotors 数据表详述了110kW电机系列选用的性能数据 TypicalMotorData典型电机数据 MotorSpeedFLCLRCLRT FLTorque rpm amps FLC FLT Ef ncy 3xFLCA14701916002639365 8B147518460019093 547 5C14751915701509241 6D148018766019094 539 2E14701855501209236F14701916701509330 1G14801907802009429 6H147518285022093 527 4I14801906701209424 SampleOfTypical110kWMotors Maximummotorstartcurrentunderfullvoltagestartconditionsisdefinedbythemotor sLockedRotorCurrent LRC 全电压起动条件下最大电机起动电流是由电机锁定转子电流 LRC 确定的 LRClevelsvaryconsiderablybetweenmotors LRC等级在电机间有显著变化 Intheexample MotorHwilldraw55 morecurrentatstartthanMotorE 在实例中 电机H引入的起动电流比电机E多55 StartCurrent起动电流 MotorSpeedFLCLRCLRT FLTorque rpm amps FLC FLT Ef ncy 3xFLCA14701916002639365 8B147518460019093 547 5C14751915701509241 6D148018766019094 539 2E14701855501209236F14701916701509330 1G14801907802009429 6H147518285022093 527 4I14801906701209424 LRCrangesfrom550 to850 SampleOfTypical110kWMotors Motorstarttorqueperformanceisindicatedbythemotor sLockedRotorTorque LRT figure 电机起动扭矩性能是由电机的锁定转子扭矩 LRT 图表示的 LRTlevelsvaryconsiderablybetweenmotors LRT等级在各个电机间有显著变化 Intheexample MotorAproducestwiceasmuchtorqueduringstartasMotorI 在实例中 电机A起动时产生的扭矩是电机I的两倍 StartTorque起动扭矩 MotorSpeedFLCLRCLRT FLTorque rpm amps FLC FLT Ef ncy 3xFLCA14701916002639365 8B147518460019093 547 5C14751915701509241 6D148018766019094 539 2E14701855501209236F14701916701509330 1G14801907802009429 6H147518285022093 527 4I14801906701209424 LRTrangesfrom120 to263 SampleOfTypical110kWMotors LRC LRTmustbeconsideredtogetherwhendeterminingamotor sstartperformance 确定电机起动性能时必须合并考虑LRC LRT Theexampledoesthisbyrankingthemotorsaccordingtothetorqueproducedat3xFLC 实例中的作法是根据3 FLC产生的扭矩对电机排序 LRC LRTWorkTogetherLRC LRT同时运转 MotorSpeedFLCLRCLRT FLTorque rpm amps FLC FLT Ef ncy 3xFLCA14701916002639365 8B147518460019093 547 5C14751915701509241 6D148018766019094 539 2E14701855501209236F14701916701509330 1G14801907802009429 6H147518285022093 527 4I14801906701209424 SampleOfTypical110kWMotors Torquedevelopedat3xFLC MotorSpeedFLCLRCLRT FLTorque rpm amps FLC FLT Ef ncy 3xFLCA14701916002639365 8B147518460019093 547 5C14751915701509241 6D148018766019094 539 2E14701855501209236F14701916701509330 1G14801907802009429 6H147518285022093 527 4I14801906701209424 Torqueisreducedbythesquareofthecurrentreduction 扭矩减少值是电流降底值的平方 MotorsB Gproducealmostthesametorqueatfullvoltage 电机B和G在满电压情况下产生的扭矩几乎相同 MotorBproduces60 morestarttorqueat3xFLC 电机B在3xFLC条件下产生的起动扭矩多60 ReducedVoltageStartingAmplifiesMotorDifferences降压起动扩大电机差异 SampleOfTypical110kWMotors MotorLRCLRTTORQUE FLC FLT 3XFLCA60026365 8B600190C570150D660190 Followtheexampleandcalculatethestarttorqueat3xFLCformotorsB C D 依照实例 计算电机B C和D在3xFLC条件下的起动扭矩 HowToCalculateStartTorque如何计算起动扭矩 2 65 8 x 47 5 41 5 39 3 SelectingamotorwithlowLockedRotorCurrent LRC andhighLockedRotorTorque LRT will 选择低锁定转子电流 LRC 和高锁定转子扭矩 LRT 电机将 Reducestartcurrent 降低起动电流Increasestarttorque 增加起动扭矩Reducesoftstartercost 降低软起动器的成本 Summary总结 CurrentrisesinstantaneouslytoLRClevels Thiscausesacurrenttransientthatcanhaveundesirableeffectsonthesupply 电流瞬间上升至LRC水平 由此引起的电流瞬变可对电源产生不良的影响Currentgraduallyfallsasmotorspeedincreases 电机速度增加时电流下降 Motorloadingaffectsonlythetimetakenforacceleration notthemagnitudeofcurrentwhichisalwaysLRC 电机负载只影响加速所需的时间 而不影响始终为LRC的电流值 FullVoltageStarting满电压起动 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT FullVoltageStarting满电压起动 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT TorquerisesinstantaneouslytoLRTlevels Thiscausesatorquetransientthatcanbedamaging 电流瞬间上升至LRC水平 由此引起的电流瞬变具有破坏性 TypicaltorquefallsfromLRTtoPullOutTorquebeforerisingtoBreakdownTorquejustbeforefullspeed 电机达到满速前 典型转矩在升至失步转矩前由LRT降至脱扣力矩 FullVoltageStartingLimitations满电压起动限制 ReducedVoltageStarting降压起动 ReducedVoltageStarting降压起动 Tobeeffective areducedvoltagestartermustallowthemotortoacceleratetoaround90 speedbeforeapplyingfullvoltage 为确保有效运行 降压起动器须使电机在使用满电压之前加速到90 左右BelowthisspeedthecurrentwillstepthroughtoalmostLRClevelsthusremovinganybenefitfromthereducedvoltagestarter 如果低于此速度 电流将逐步达到LRC水平 从而失去降压起动器的任何优点 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT Electromechanical机电 Auto transformer自耦变压器 PrimaryResistance一次电路电阻 Star Delta星形 三角形Electronic电子 SoftStart软起动 ReducedVoltageStarters降压起动器 Auto transformers自耦变压器 TheAuto transformerStarteremploysanauto transformertoreducethevoltageduringthestartperiod Thetransformerhasarangeofoutputvoltagetapsthatcanbeusedtosetthestartvoltage 超动期间自耦变压器起动器使用自耦变压器降低电压 变压器有一套输出电压开关 可用以设置起动电压 Themotorcurrentisreducedbythestartvoltagereduction andfurtherreducedbythetransformeractionresultinginalinecurrentlessthantheactualmotorcurrent 电机电流随起动电压下降而降低 且通过变压器的作用进一步降低最后产生的线路电流小于电机实际电流 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT 60 Tap60 分接头 Auto transformers自耦变压器 Limitations Limitedvoltagetaps Limitednumberofstartsperhour TorquereducedatallspeedsCostly限制 限定电压分接头 限定每小时的起动次数 在所有速度下扭矩值降低 价值高 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT 50 Tap50 分接头Theinitialstartvoltageissetbytapselection andthestarttimeiscontrolledbyatimer Ifthestartvoltageistoolow orthestarttimeincorrectlyset thetransitiontofullvoltagewilloccurwiththemotoratlessthanfullspeed resultinginahighcurrentandtorquestep 初始起动电压是由分接头选择设定的 而起动时间是由定时器控制的 如果起动电压太低或起动时间设置不正确 变至满电压的过程将发生在电机未达全速之时 因此导致高电流和扭矩步进 Auto transformers自耦变压器 PrimaryResistance一次电路电阻 Resistorsareconnectedinserieswitheachphase betweentheisolationcontactorandthemotor Thevoltagedropacrosstheresistorsresultsinareducedvoltageappliedtothemotor thusreducingstartcurrentandtorque 电阻器与隔离接触器和电机之间的每一相实行串接 电阻器降压导致电机降压 从而降低起动电流和扭矩 Setfor4xFLCstartcurrent 设置4xFLC起动电流 PrimaryResistance一次电路电阻 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT Limitations Difficulttochangeresistance Dissipatealotofheat Limitednumberofstartsperhour StartcharacteristicschangebetweenstartsifresistorshavenottotallycooledHardtostarthighinertialoads限制 很难改变电阻 大量散热 限定每小时的起动次数 如果电阻器没有完全冷却 起动特性会在各起动间发生差异 难以起动高惯性负载 PrimaryResistance一次电路电阻 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT Setfor3 5xFLCstartcurrent 设置3 5xFLC起动电流 Startvoltageisdeterminedbytheresistorsused Iftheresistanceistoohightherewillbeinsufficienttorquetoacceleratethemotortofullspeed 起动电压是由所使用的电阻器确定的 如果电阻太高 则扭矩不足以加速电机达到全速 Thereducedvoltagestarttimeiscontrolledbyapresettimer Ifthetimeistooshort themotorwillnothaveachievedfullspeedbeforetheresistorsarebridged 降压起动时间是由预置计时器控制的 如果时间太短 电机不会在电阻器跨接之前达到全速 Star Delta星形 三角形 Motor3 ThermalOverload StarContactor DeltaContactor MainContactor Themotorisinitiallyconnectedinstarconfigurationandthen afterapresettime themotorisdisconnectedfromthesupplyandreconnectedindeltaconfiguration Thecurrentandtorqueinthestarconfigurationareonethirdofthefullvoltagecurrentandtorquewhenthemotorisconnectedindelta 电机最初以星形配置进行连接 然后 在预设时间之后 电机会与电源断开 并再次以三角形配置进行连接 当电机以三角形连接时 则星形配置电流和扭矩是满电压电流和扭矩的三分之一 Limitations Noadjustmentpossible Opentransitionswitchingbetweenstaranddeltacausesdamagingcurrentandtorquetransients 限制 不能调节 星形和三角形之间的开路瞬变会破坏电流和扭矩瞬变 Star Delta星形 三角形 0 50 100 150 200 250 300 100 90 80 70 60 50 40 30 20 10 0 SLIP FULLLOADTORQUE 0 100 200 300 400 500 600 700 CURRENT Insufficienttorquetoacceleratethisloadinstarconfiguration 不足的扭矩以星形配置加速该负载 OpenTransitionSwitching Occurswhenthestartergoesthroughanopencircuitstageintheswitchingsequence Stage 1 connectiontothereducedvoltage 2 disconnectfromthereducedvoltage opencircuit 3 connecttothefullvoltage Opentransitionstartingcausesseverecurrent torquetransientsthatcanbemoredetrimentaltothesupplyandthemechanicalequipmentthanfullvoltagestarting Whenthemotorisspinningandthendisconnectedfromthesupply itactsasagenerator Outputvoltagecanbethesameamplitudeasthesupply Atthetimeofreclosetherecanstillbesignificantvoltagepresentatthemotorterminals Voltagegeneratedbythemotorattheinstantofreclosemaybeequaltothesupplyvoltagebutexactlyoutofphase Thisequatestoreclosingwithtwicethesupplyvoltageonthemotor Theresultisacurrentoftwicelockedrotorcurrentandatorquetransientoffourtimeslockedrotortorque 开路瞬变转换 当起动器以转换顺序通过开路段时发生 1 连接降压 2 与降压 开路 断开 3 连接满电压 开路瞬变起动造成严重的电流和扭矩瞬变 这对电源和机械设备可能比满电压起动更加有害 当电机旋转 然后与电源断开时 起到发电机的作用 输出电压可与电源振幅相同 再合闸时 仍可有明显的电压出现在电机终