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中国地质大学长城学院本科设计外文资料翻译院别工程技术学院学生姓名尹靖怡专业电气工程及其自动化学号043130136年月日2022417外文翻译译文三相感应电动机速度控制方法三相异步电动机转速公式为从上式可见,改变供电频率、电动机的极对数及转差率均可大到改变转n=60f/p1-s fp s速的目的从调速的本质来看,不同的调速方式无非是改变交流电动机的同步转速或者不改变同步转两种在生产机械中广泛使用不改变同步转速的调速方法有绕线式电动机的转子串电阻调速、斩波调速、串级调速以及应用电磁转差离合器、液力偶合器、油膜离合器等调速改变同步转速的有改变定子极对数的多速电动机,改变定子电压、频率的变频调速有能无换向电动机调速等从调速时的能耗观点来看,有高效调速方法与低效调速方法两种高效调速指时转差率不变,因此无转差损耗,如多速电动机、变频调速以及能将转差损耗回收的调速方法如串级调速等有转差损耗的调速方法属低效调速,如转子串电阻调速方法,能量就损耗在转子回路中;电磁离合器的调速方法,能量损耗在离合器线圈中;液力偶合器调速,能量损耗在液力偶合器的油中普通来说转差损耗随调速范围扩大而增加,如果调速范围不大,能量损耗是很小的
一、变极对数调速方法这种调速方法是用改变定子绕组的接红方式来改变笼型电动机定子极对数达到调速目的,特点如下、具有较硬的机械特性,稳定性良好;
1、无转差损耗,效率高;
2、接线简单、控制方便、价格低;
3、有级调速,级差较大,不能获得平滑调速;
4、可以与调压调速、电磁转差离合器配合使用,获得较高效率的平滑调速特性5本方法合用于不需要无级调速的生产机械,如金属切削机床、升降机、起重设备、风机、水泵等
二、变频调速方法变频调速是改变电动机定子电源的频率,从而改变其同步转速的调速方法变频调速系统主要设备是提供变频电源的变频器,变频器可分成交流一直流一交流变频器和交流一交流变频器两大类,目前国内大都使用交一直一交变频器其特点、效率高,调速过程中没有附加损耗;
1、应用范围广,可用于笼型异步电动机;
2、调速范围大,特性硬,精度高;
3、技术复杂,造价高,维护检修艰难4本方法合用于要求精度高、调速性能较好场合
三、串级调速方法串级调速是指绕线式电动机转子回路中串入可调节的附加电势来改变电动机的转差,达到调速的目的大部份转差功率被串入的附加电势所吸收,再利用产生附加的装置,把吸收的转差功率返回电网或者转换能量加以利用根据转差功率吸收利用方式,串级调速可分为机电串级调速、机械串级调速及晶闸管串级调速形式,多采用晶闸管串级调速,其特点为、可将调速过程中的转差损耗回馈到电网或者生产机械上,效率较高;
1、装置容量与调速范围成正比,投资省,合用于调速范围在额定转速的生产270%-90%机械上;、调速装置故障时可以切换至全速运行,避免停产;
3、晶闸管串级调速功率因数偏低,谐波影响较大;4本方法适合于风机、水泵及轧钢机、矿井提升机、挤压机上使用
四、绕线式电动机转子串电阻调速方法绕线式异步电动机转子串入附加电阻,使电动机的转差率加大,电动机在较低的转速下运行串入的电阻越大,电动机的转速越低此方法设备简单,控制方便,但转差功率以发热的形式消耗在电阻上属有级调速,机械特性较软
五、定子调压调速方法当改变电动机的定子电压时,可以得到一组不同的机械特性曲线,从而获得不同转速由于电动机的转矩与电压平方成正比,因此最大转矩下降不少,其调速范围较小,使普通笼型电动机难以应用为了扩大调速范围,调压调速应采用转子电阻值大的笼型电动机,如专供调压调速用的力矩电动机,或者在绕线式电动机上串联频敏电阻为了扩大稳定运行范围,当调速在以上的场合应采用反馈控制以达到自动调节转速目的调压调速的主要装置21是一个能提供电压变化的电源,目前常用的调压方式有串联饱和电抗器、自耦变压器以及晶闸管调压等几种晶闸管调压方式为最佳调压调速的特点、调压调速路线简单,易实现自动控制
1、调压过程中转差功率以发热形式消耗在转子电阻中,效率较低2调压调速普通合用于以下的生产机械100KW
六、电磁调速电动机调速方法电磁调速电动机由笼型电动机、电磁转差离合器和直流励磁电源(控制器)三部份组成直流励磁电源功率较小,通常由单相半波或者全波晶闸管整流器组成,改变晶闸管的导通角,可以改变励磁电流的大小电磁转差离合器由电枢、磁极和励磁绕组三部份组成电枢和后者没有机械联系,都能自由转动电枢与电动机转子同轴联接称主动部份,由电动机带动;磁极用联轴节与负载轴对接称从动部份当电枢与磁极均为静止时,如励磁绕组通以直流,则沿气隙圆周表面将形成若干对、极性交替的磁极,其磁通经过电枢当电枢随拖动电N S动机旋转时,由于电枢与磁极间相对运动,于是使电枢感应产生涡流,此涡流与磁通相互作用产生转矩,带动有磁极的转子按同一方向旋转,但其转速恒低于电枢的转速这是一种N1,转差调速方式,变动转差离合器的直流励磁电流,便可改变离合器的输出转矩和转速电磁调速电动机的调速特点、装置结构及控制路线简单、运行可靠、维修方便;
1、调速平滑、无级调速;
2、对电网无谐影响;
3、速度失大、效率低4本方法合用于中、小功率,要求平滑动、短时低速运行的生产机械
七、液力耦合器调速方法液力耦合器是一种液力传动装置,普通由泵轮和涡轮组成,它们统称工作轮,放在密封壳体中壳中充入一定量的工作液体,当泵轮在原动机带动下旋转时,处于其中的液体受叶片推动而旋转,在离心力作用下沿着泵轮外环进入涡轮时,就在同一转向上给涡轮叶片以推力,使其带动生产机械运转液力耦合器的动力转输能力与壳内相对充液量的大小是一致的在工作过程中,改变充液率就可以改变耦合器的涡轮转速,作到无级调速,其特点为、功率适应范围大,可满足从几十千瓦至数千千瓦不同功率的需要;
1、结构简单,工作可靠,使用及维修方便,且造价低;
2、尺寸小,能容大;
3、控制调节方便,容易实现自动控制4本方法合用于风机、水泵的调速外文翻译原文The three-phase inductionmotor speed control rrethodThree-phase asynchronousmotor speedformula:N=60f/p1-s Canbe seenfrom theab oveformula,change the power supplyfrequency f,motor polenumber pand theslip smay bet oomuchto change the speed of purpose.From the speed of the essenceof view,is simplya different way tochange speedsynchronous ACmotor doesnot change the synctransfer speedor two.Widespread usein productionmachines withoutchanging thesynchronous speedof motorspeed control methodWound RotorSeries ResistanceSpeed,chopper speed control,cascade control,and applicationof electromagnetic slip clutch,fluid couplings,clutches andother filmspe ed.Change thesynchronous speedof changeon thenumber of stator polemulti-speed motorto changethe stator voltageand frequencyto frequencyconversion withno changeto the motor speed andsoon.Energy from the speedpoint ofview when,with high speed methodand inefficientmethod softwo kindsof speed:highspeed when theslip refersto thesame,so noslip losses,such asmulti-speed motors,Slip frequencycontrol andloss canspeed recoverymethods such as cascadecontrol,etc..A deterioratingloss of speed control methods areinefficient speed,such asseriesresistance of the rotorspeed method,the energy loss in the rotorcircuit on;Electromagnetic ClutchThe speedmethod,the energyloss in the clutchcoils;fluid couplingspeed,energylossint he fluidcouplingof theoil.General deterioration in lossincreased with the expansionspeed range,if notspeed range,the energyloss isminimal.1,variable speed control method of polepairsThis speed is thenused to change thestator windingwaytochangethered cage motor stat orpole pairsto achievespeedcontrolpurposes,the followingfeaturesWith hardmechanical properties,good stability;No sliploss,high efficiency;Wiring simple,easy tocontrol,low price;A levelspeed,diff erentiallarge,can notget smoothspeedcontrol;With pressure and speed adjustment,with theuse ofelectromagneticslipclutch,smooth andefficient accessto highspeed characteristics.This methodis suitablefor theproduction doesnotrequire variablespeed machinery,such asmetal cuttingmachine Bed,Lift,Lifting equipmerit,FansWater PumpAnd soon.2,Frequency ControlMethod Frequency control istochangethe motorstator Powersupp lyFrequency,thus changing the speedof itssynchronous speedmethod.Frequencycontrolsyst emmainequipment isto providevariable frequencypower supplyInverter,Inverter can be divided intoAC-DC-AC inverterand AC-AC convertertwo categories,mos tof thecurrent domesticuse ofAC-DC-AC inverter.Its characteristicsHighefficiency,speed theprocess withoutadditional loss;Wide rangeof applications,can beused forcage inductionmotor;;var cprojDsid=Hu2787156”;var cprojDSwidth=966”;var cpro_psheight=H120”Speed range,features ahard,high accuracy;Technical complexity,high cost,difficult maintenanceand overhaul.This methodis suitablefor thehigh accuracy,good speedperformance occasions.3,cascade controlmethod Cascadecontrol iswound into the rotorcircuit inthe seriesofadditional potentialcan beadjusted tochangethe motors slip,to achievespeedcontrolpurpose s.Most ofthe deteriorationin power to bein serieswiththeadded potentialabsorbed,re-use generatesadditional devicesto absorbthe deteriorationin powerto returnpowertouse orconvers ionofenergy.Slip-power absorptionunder way,cascade controlcanbedividedintoMotor Cascadecontrol,mechanical andthyristor cascadecontrol cascadecontrol,and multi-use cascadec ontrolthyristor,characterized byCanspeed theprocess ofdeteriorationinloss offeedback toth enetworkor productionmachinery,more efficient;Installed capacityand speedrange indirect proportionto investment,applicablespeed range70%-90%rated speedof production machinery;peed devicefailure canswit chtofull speed,to avoidthe cut-off;Thyristor cascadespeed lowpower factor,harmonics greaterimpact.This methodis suitablefor fans,pumps androlling mills,mine hoist,extrusion machines.4,wound rotormotor speedcontrolmethodof SeriesResistanceWound RotorMotor additionalresistance in series,so thatthe motorslip up,motorrunning atlow speed.The greaterthe resistance inseries,themotorspeedislower.This methodis simple,easy tocontrol,but deterioratethepowerconsumption inthe formof heatinth eresistor.Is aclass speed,soft mechanicalproperties5,thestatorpressure andspeed adjustmentmethodStator voltagewhen changingthemotor,you canget adifferent setof mechanicalproperti esofcurves,which weredifferent speeds.Since themotor torqueand voltageproportional tothesquare,the largestdecline ina lotof torque,speedrangeof itssmall cage motors ingeneral and difficulttoapply.In orderto expandthe speedrange,pressureandspeed adjustmentshould be largerrotorresistance valuecage motors,such asdedicated voltageregulator withspeed torquemotor,orseries woundmotor frequencysensitive resistors.In orderto expandthe rangeofstable operation,when thespeedof2:1or moreoccasions inthe feedbackcontrol shouldbe adopted toachieve thepurposeof automaticadjustment ofspeed.Pressure andspeed adjustmentis akey deviceto providepower supplyvoltage,the currentwayof atandem commonsaturation voltageregulator Reactor,Auto TransformerAnd severalotherThyristor Surge.Thyristor Surgeis thebest way.Adjusting SpeedfeaturesPressure ands peedadjustmentcircuit is simple,easy torealize automaticcontrol;Poor powersurge processtoheattransfer inthe rotorresistanceinthe formof consumption,low efficiency.Pressure andspeedadjustmentgenerally applies to10OKW belowproduction machinery.6,Electromagnetic speedregulating motorspeedcontrolmethodofelectromagnetic speedregulating electricmotor squirrelcagemotor,electric slipclutch andDC excitationpower supplyController consistsof three parts.DC excitationpower small,usually consistingof singlephasehalf-wave orfull waverectifiers thyristorscomposition,change thyristorconduction angle,you canchangethe magnetizingcurrent size.Electromagnetic slipclutch armature,poles andexcitation windingscomposed ofthreeparts.Armature andthe latterhas nomechanical contact,are freeto rotate.Armature motorcoaxial connectionactive part,driven bymotors;docking withthe loadax ismagneticpole couplingfromthemoving parts.When the armature polesare atrest,suchasexcitation windingsfor DC,along thecircumferential surfacewill forma numberof airgap onthen,s,of alternatingpolarity poles,the magneticflux throughthearmature.Dang electricarma turewithdrag motorrotating Shi,due toelectric armatureand polebetween relativemovement,and makeselectricarmature inductionproduced Eddy,this Eddyand magneticpass mutualrol eproduced gomoments,led haspole ofrotor bysame directionrotating,but itsspeed constantbelow electricarmatureofspeedN1,this isa godifference adjustablespeed way,changes godi fferenceclutchdevice ofDC Laimagnetic current,will can change clutchdevice ofoutput gomoments andspeed.Characteristics ofelectromagnetic speedregulating motorspeed:Appliances,structure andcontrol circuitissimple,reliable operation,easy maintenance;sp eedandsmooth,stepless speedregulation thepower networkharmonic effects;lost speed,lowefficiency.This methodapplies tomedium andsmall power,requires lowspeedwhenthe smooth,sho rtrunproductionmachinery.7,The hydrauliccoupler speedregulating hydraulicCoupler isa devicefor hydraulicdrive,ismade upofthepump andturbine,they collectivelywork wheels,placed ina sealedcase.Shell filledwitha certainamount ofworking fluid,when pumpis impulsedriven byrotation,in whichliquidpropelled byblades whichrotate,and underthe actionof centrifugalforce alongthe outerwheelswhen enteringthe turbinepump,to thrusttotheturbine bladeson thesame turn,make itdriveproduction machineryrunning.Power transfercapacity ofthe hydrauliccoupler andshell filledwithfluid volumesizes areconsistent.In thecourse ofwork,changingthefilling ratecanchangethecoupler ofturbine speed,stemless speedregulation,characterized by:Power scope,can meetthe needsof froma coupleof differentpower10-kilowatt toshuqianqian;Simple structure,reliable performance,easy tooperation andmaintenance,and lowcost;Small size,capacity;Easy toadjust,easy tofulfill automaticcontrol.This methodappliestothespeedofthefan andwater pump.。