机械专业外文翻译(中英文翻译)

外文翻译英文原文BeltConveyingSystemsDevelopmentofdrivingsystemAmongthemethodsofmaterialconveyingemployed，beltconveyorsplayaveryimportantpartinthereliablecarryingofmaterialoverlongdistancesatcompetitivecost．Conveyorsystemshavebecomelargerandmorecomplexanddrivesystemshavealsobeengoingthroughaprocessofevolutionandwillcontinuetodoso．Nowadays，biggerbeltsrequiremorepowerandhavebroughttheneedforlargerindividualdrivesaswellasmultipledrivessuchas3drivesof750kWforonebelt(thisisthecasefortheconveyordrivesinChengzhuangMine)．Theabilitytocontroldriveaccelerationtorqueiscriticaltobeltconveyors’performance．Anefficientdrivesystemshouldbeabletoprovidesmooth，softstartswhilemaintainingbelttensionswithinthespecifiedsafelimits．Forloadsharingonmultipledrives．torqueandspeedcontrolarealsoimportantconsiderationsinthedrivesystem’sdesign.Duetotheadvancesinconveyordrivecontroltechnology，atpresentmanymorereliable．Cost-effectiveandperformance-drivenconveyordrivesystemscoveringawiderangeofpowerareavailableforcustomers’choices[1].1Analysisonconveyordrivetechnologies1．1DirectdrivesFull-voltagestarters．Withafull-voltagestarterdesign，theconveyorheadshaftisdirect-coupledtothemotorthroughthegeardrive．Directfull-voltagestartersareadequateforrelativelylow-power,simple-profileconveyors．Withdirectfu11-voltagestarters．nocontrolisprovidedforvariousconveyorloadsand．dependingontheratiobetweenfu11-andno-1oadpowerrequirements，emptystartingtimescanbethreeorfourtimesfasterthanfullload．Themaintenance-freestartingsystemissimple，low-costandveryreliable．However,theycannotcontrolstartingtorqueandmaximumstalltorque；therefore．theyarelimitedtothelow-power,simple-profileconveyorbeltdrives．Reduced-voltagestarters．Asconveyorpowerrequirementsincrease，controllingtheappliedmotortorqueduringtheaccelerationperiodbecomesincreasinglyimportant．Becausemotortorque1safunctionofvoltage，motorvoltagemustbecontrolled．Thiscanbeachievedthroughreduced-voltagestartersbyemployingasiliconcontrolledrectifier(SCR)．AcommonstartingmethodwithSCRreduced-voltagestartersistoapplylowvoltageinitiallytotakeupconveyorbeltslack．andthentoapplyatimedlinearrampuptofullvoltageandbeltspeed．However,thisstartingmethodwillnotproduceconstantconveyorbeltacceleration．Whenaccelerationiscomplete．theSCRs,whichcontroltheappliedvoltagetotheelectricmotor．arelockedinfullconduction,providingfu11-linevoltagetothemotor．Motorswithhighertorqueandpull—uptorque，canprovidebetterstartingtorquewhencombinedwiththeSCRstarters,whichareavailableinsizesupto750KW．Woundrotorinductionmotors．WoundrotorinductionmotorsareconnecteddirectlytothedrivesystemreducerandareamodifiedconfigurationofastandardACinductionmotor．Byinsertingresistanceinserieswiththemotor’srotorwindings．themodifiedmotorcontrolsystemcontrolsmotortorque．Forconveyorstarting，resistanceisplacedinserieswiththerotorforlowinitialtorque．Astheconveyoraccelerates，theresistanceisreducedslowlytomaintainaconstantaccelerationtorque．Onmultiple-drivesystems．anexternalslipresistormaybeleftinserieswiththerotorwindingstoaidinloadsharing．Themotorsystemshavearelativelysimpledesign．However,thecontrolsystemsforthesecanbehighlycomplex，becausetheyarebasedoncomputercontroloftheresistanceswitching．Today，themajorityofcontrolsystemsarecustomdesignedtomeetaconveyorsystem’sparticularspecifications．Woundrotormotorsareappropriateforsystemsrequiringmorethan400kW．DCmotor．DCmotors．availablefromafractionofthousandsofkW，aredesignedtodeliverconstanttorquebelowbasespeedandconstantkWabovebasespeedtothemaximumallowablerevolutionsperminute(r/min)．withthemajorityofconveyordrives,aDCshuntwoundmotorisused．Whereinthemotor’srotatingarmatureisconnectedexternally．ThemostcommontechnologyforcontrollingDCdrivesisaSCRdevice．whichallowsforcontinualvariable-speedoperation．TheDCdrivesystemismechanicallysimple,butcanincludecomplexcustom-designedelectronicstomonitorandcontrolthecompletesystem．Thissystemoptionisexpensiveincomparisontoothersoft-startsystems．butitisareliable,cost-effectivedriveinapplicationsinwhichtorque,1oadsharingandvariablespeedareprimaryconsiderations．DCmotorsgenerallyareusedwithhigher-powerconveyors，includingcomplexprofileconveyorswithmultiple-drivesystems，boostertrippersystemsneedingbelttensioncontrolandconveyorsrequiringawidevariable-speedrange．1．2HydrokineticcouplingHydrokineticcouplings，commonlyreferredtoasfluidcouplings．arecomposedofthreebasicelements;thedrivenimpeller,whichactsasacentrifugalpump；thedrivinghydraulicturbineknownastherunnerandacasingthatenclosesthetwopowercomponents．Hydraulicfluidispumpedfromthedrivenimpellertothedrivingrunner,producingtorqueatthedrivenshaft．Becausecirculatinghydraulicfluidproducesthetorqueandspeed，nomechanicalconnectionisrequiredbetweenthedrivinganddrivenshafts．Thepowerproducedbythiscouplingisbasedonthecirculatedfluid’samountanddensityandthetorqueinproportiontoinputspeed．Becausethepumpingactionwithinthefluidcouplingdependsoncentrifugalforces．theoutputspeedislessthantheinputspeed．Referredtoasslip．thisnormallyisbetweenl%and3%．BasichydrokineticcouplingsareavailableinconfigurationsfromfractionaltoseveralthousandkW．Fixed-fillfluidcouplings．Fixed-fillfluidcouplingsarethemostcommonlyusedsoft-startdevicesforconveyorswithsimplerbeltprofilesandlimitedconvex/concavesections．Theyarerelativelysimple,1ow-cost,reliable,maintenancefreedevicesthatprovideexcellentsoftstartingresultstothemajorityofbeltconveyorsinusetoday．Variable-filldraincouplings．Drainable-fluidcouplingsworkonthesameprincipleasfixed-fillcouplings．Thecoupling’simpellersaremountedontheACmotorandtherunnersonthedrivenreducerhigh-speedshaft．Housingmountedtothedrivebaseenclosestheworkingcircuit．Thecoupling’srotatingcasingcontainsbleed-offorificesthatcontinuallyallowfluidtoexittheworkingcircuitintoaseparatehydraulicreservoir．Oilfromthereservoirispumpedthroughaheatexchangertoasolenoid-operatedhydraulicvalvethatcontrolsthefillingofthefluidcoupling．Tocontrolthestartingtorqueofasingle-driveconveyorsystem，theACmotorcurrentmustbemonitoredtoprovidefeedbacktothesolenoidcontrolvalve．Variablefilldraincouplingsareusedinmediumtohigh-kWconveyorsystemsandareavailableinsizesuptothousandsofkW．Thedrivescanbemechanicallycomplexanddependingonthecontrolparameters．thesystemcanbeelectronicallyintricate．Thedrivesystemcostismediumtohigh,dependinguponsizespecified．Hydrokineticscoopcontroldrive．Thescoopcontrolfluidcouplingconsistsofthethreestandardfluidcouplingcomponents：adrivenimpeller,adrivingrunnerandacasingthatenclosestheworkingcircuit．Thecasingisfittedwithfixedorificesthatbleedapredeterminedamountoffluidintoareservoir．Whenthescooptubeisfullyextendedintothereservoir,thecouplingisl00percentfilled．Thescooptube,extendingoutsidethefluidcoupling，ispositionedusinganelectricactuatortoengagethetubefromthefullyretractedtothefullyengagedposition．Thiscontrolprovidesreasonablysmoothaccelerationrates．tobutthecomputer-basedcontrolsystemisverycomplex．Scoopcontrolcouplingsareappliedonconveyorsrequiringsingleormultipledrivesfroml50kWto750kW.1．3Variable-frequencycontrol(VFC)Variablefrequencycontrolisalsooneofthedirectdrivemethods．Theemphasizingdiscussionaboutithereisbecausethatithassouniquecharacteristicandsogoodperformancecomparedwithotherdrivingmethodsforbeltconveyor．VFCdevicesProvidevariablefrequencyandvoltagetotheinductionmotor,resultinginanexcellentstartingtorqueandaccelerationrateforbeltconveyordrives．VFCdrives．availablefromfractionaltoseveralthousand(kW),areelectroniccontrollersthatrectifyAClinepowertoDCand，throughaninverter,convertDCbacktoACwithfrequencyandvoltagecontro1．VFCdrivesadoptvectorcontrolordirecttorquecontrol(DTC)technology，andcanadoptdifferentoperatingspeedsaccordingtodifferentloads．VFCdrivescanmakestartingorstallingaccordingtoanygivenS-curves．realizingtheautomatictrackforstartingorstallingcurves．VFCdrivesprovideexcellentspeedandtorquecontrolforstartingconveyorbelts．andcanalsobedesignedtoprovideloadsharingformultipledrives．easilyVFCcontrollersarefrequentlyinstalledonlower-poweredconveyordrives，butwhenusedattherangeofmedium-highvoltageinthepast．thestructureofVFCcontrollersbecomesverycomplicatedduetothelimitationofvoltageratingofpowersemiconductordevices，thecombinationofmedium-highvoltagedrivesandvariablespeedisoftensolvedwithlow-voltageinvertersusingstep-uptransformerattheoutput，orwithmultiplelow-voltageinvertersconnectedinseries．Three-levelvoltage-fedPWMconvertersystemsarerecentlyshowingincreasingpopularityformulti-megawattindustrialdriveapplicationsbecauseofeasyvoltagesharingbetweentheseriesdevicesandimprovedharmonicqualityattheoutputcomparedtotwo-levelconvertersystemsWithsimpleseriesconnectionofdevices．ThiskindofVFCsystemwiththree750kW/2．3kVinvertershasbeensuccessfullyinstalledinChengZhuangMineforone2．7-kmlongbeltconveyordrivingsysteminfollowingtheprincipleofthree-levelinverterwillbediscussedindetail．2Neutralpointclamped(NPC)three-levelinverterusingIGBTsThree-levelvoltage-fedinvertershaverecentlybecomemoreandmorepopularforhigherpowerdriveapplicationsbecauseoftheireasyvoltagesharingfeatures．1owerdv/dtperswitchingforeachofthedevices，andsuperiorharmonicqualityattheoutput．TheavailabilityofHV-IGBTshasledtothedesignofanewrangeofmedium-highvoltageinverterusingthree-levelNPCtopology．Thiskindofinvertercanrealizeawholerangewithavoltageratingfrom2．3kVto4．16kVSeriesconnectionofHV-IGBTmodulesisusedinthe3．3kVand4．16kVdevices．The2．3kVinvertersneedonlyoneHV-IGBTperswitch[2,3].2．1PowersectionTomeetthedemandsformediumvoltageapplications．athree-levelneutralpointclampedinverterrealizesthepowersection．Incomparisontoatwo-levelinverter．theNPCinverteroffersthebenefitthatthreevoltagelevelscanbesuppliedtotheoutputterminals，soforthesameoutputcurrentquality，only1/4oftheswitchingfrequencyisnecessary．MoreoverthevoltageratingsoftheswitchesinNPCinvertertopologywillbereducedto1/2．andtheadditionaltransientvoltagestressonthemotorcanalsobereducedto1/2comparedtothatofatwo-levelinverter．Theswitchingstatesofathree-levelinverteraresummarizedinTable1．U．VandWdenoteeachofthethreephasesrespectively；PNandOarethedcbuspoints．ThephaseU，forexample，isinstateP(positivebusvoltage)whentheswitchesS1uandS2uareclosed，whereasitisinstateN(negativebusvoltage)whentheswitchesS3uandS4uareclosed．Atneutralpointclamping，thephaseisinOstatewheneitherS2uorS3uconductsdependingonpositiveornegativephasecurrentpolarity，respectively．Forneutralpointvoltagebalancing，theaveragecurrentinjectedatOshouldbezero．2．2LinesideconverterForstandardapplications．al2-pulsedioderectifierfeedsthedividedDC-linkcapacitor．Thistopologyintroduceslowharmonicsonthelineside．Forevenhigherrequirementsa24-pulsedioderectifiercanbeusedasaninputconverter．Formoreadvancedapplicationswhereregenerationcapabilityisnecessary,anactivefront．endconvertercanreplacethedioderectifier,usingthesamestructureastheinverter．2．3InvertercontrolMotorContro1．Motorcontrolofinductionmachinesisrealizedbyusingarotorflux．orientedvectorcontroller．Fig．2showstheblockdiagramofindirectvectorcontrolleddrivethatincorporatesbothconstanttorqueandhighspeedfield-weakeningregionswherethePWMmodulatorwasused．Inthisfigure，thecommandfluxisgeneratedasfunctionofspeed．Thefeedbackspeedisaddedwiththefeedforwardslipcommandsignal.theresultingfrequencysignalisintegratedandthentheunitvectorsignals(cosandsin)aregenerated．ThevectorrotatorgeneratesthevoltageandanglecommandsforthePWMasshown．PWMModulator．ThedemandedvoltagevectorisgeneratedusinganelaboratePWMmodulator．Themodulatorextendstheconceptsofspace-vectormodulationtothethree-levelinverter．Theoperationcanbeexplainedbystartingfromaregularlysampledsine-trianglecomparisonfromtwo-levelinverter．Insteadofusingonesetofreferencewaveformsandonetriangledefiningtheswitchingfrequency，thethree-levelmodulatorusestwosetsofreferencewaveformsUr1andUr2andjustonetriangle．Thus,eachswitchingtransitionisusedinanoptimalwaysothatseveralobjectivesarereachedatthesametime．Verylowharmonicsaregenerated．Theswitchingfrequencyislowandthusswitchinglossesareminimized．Asinatwo-levelinverter,azero-sequencecomponentcanbeaddedtoeachsetofreferencewaveformsinordertomaximizethefundamentalvoltagecomponent．Asanadditionaldegreeoffreedom，thepositionofthereferencewaveformswithinthetrianglecanbechanged．ThiscanbeusedforcurrentbalanceinthetwohalvesoftheDC-1ink．3TestingresultsAfterSuccessfulinstallationofthree750kW/2．3kVthree-levelinvertersforone2．7kmlongbeltconveyordrivingsysteminChengzhuangMine．TheperformanceofthewholeVFCsystemwastested．Fig．3istakenfromthetest，whichshowstheexcellentcharacteristicofthebeltconveyordrivingsystemwithVFCcontroller．Fig．3includesfourcurves．Thecurve1showsthebelttension．Fromthecurveitcanbefindthatthefluctuationrangeofthebelttensionisverysmal1．Curve2andcurve3indicatecurrentandtorqueseparately．Curve4showsthevelocityofthecontrolledbelt．Thebeltvelocityhavethe“s”shapecharacteristic．A1ltheresultsofthetestshowaverysatisfiedcharacteristicforbeltdrivingsystem．4ConclusionsAdvancesinconveyordrivecontroltechnologyinrecentyearshaveresultedinmanymorereliable．Cost-effectiveandperformance-drivenconveyordrivesystemchoicesforusers．Amongthesechoices，theVariablefrequencycontrol(VFC)methodshowspromisinguseinthefutureforlongdistancebeltconveyordrivesduetoitsexcellentperformances．TheNPCthree-levelinverterusinghighvoltageIGBTsmaketheVariablefrequencycontrolinmediumvoltageapplicationsbecomemuchmoresimplebecausetheinverteritselfcanprovidethemediumvoltageneededatthemotorterminals，thuseliminatingthestep-uptransformerinmostapplicationsinthepast．ThetestingresultstakenfromtheVFCcontrolsystemwithNPCthree．1evelinvertersusedina2．7kmlongbeltconveyordrivesinChengzhuangMineindicatesthattheperformanceofNPCthree-levelinverterusingHV-IGBTstogetherwiththecontrolstrategyofrotorfield-orientedvectorcontrolforinductionmotordriveisexcellentforbeltconveyordrivingsystem．中文译文：带式输送机及其牵引系统在运送大量的物料时，带式输送机在长距离的运输中起到了非常重要的竞争作用。输送系统将会变得更大、更复杂，而驱动系统也已经历了一个演变过程，并将继续这样下去。如今，较大的输送带和多驱动系统需要更大的功率,比方3驱动系统需要给输送带750KW(成庄煤矿输送机驱动系统的要求)。控制驱动力和加速度扭矩是输送机的关键。一个高效的驱动系统应该能顺利的运行,同时保持输送带张紧力在指定的平安极限负荷内。为了负载分配在多个驱动上，扭矩和速度控制在驱动系统的设计中也是很重要的因素。由于输送机驱动系统控制技术的进步,目前更多可靠的低本钱和高效驱动的驱动系统可供顾客选择[1]。1带式输送机驱动1.1带式输送机驱动方式全电压启动在全电压启动设计中，带式输送机驱动轴通过齿轮传动直接连接到电机。直接全压驱动没有为变化的传送负载提供任何控制,根据满载和空载功率需求的比率，空载启动时比满载可能快3～4倍。此种方式的优点是:免维护,启动系统简单，低本钱，可靠性高。但是，不能控制启动扭矩和最大停止扭矩。因此，这种方式只用于低功率,结构简单的传送驱动中。降压启动随着传送驱动功率的增加,在加速期间控制使用的电机扭矩变得越来越重要。由于电机扭矩是电压的函数,电机电压必须得到控制，一般用可控硅整流器(SCR)构成的降压启动装置，先施加低电压拉紧输送带,然后线性的增加供电电压直到全电压和最大带速。但是，这种启动方式不会产生稳定的加速度，当加速完成时,控制电机电压的SCR锁定在全导通，为电机提供全压。此种控制方式功率可到达750kW。绕线转子感应电机绕线转子感应电机直接连接到驱动系统减速机上,通过在电机转子绕组中串联电阻控制电机转矩。在传送装置启动时,把电阻串联进转子产生较低的转矩，当传送带加速时，电阻逐渐减少保持稳定增加转矩。在多驱动系统中，一个外加的滑差电阻可能将总是串联在转子绕组回路中以帮助均分负载。该方式的电机系统设计相对简单，但控制系统可能很复杂，因为它们是基于计算机控制的电阻切换。当今，控制系统的大多数是定制设计来满足传送系统的特殊规格。绕线转子电机适合于需要400kW以上的系统。直流(DC)电机大多数传送驱动使用DC并励电机，电机的电枢在外部连接。控制DC驱动技术一般应用SCR装置，它允许连续的变速操作。DC驱动系统在机械上是简单的,但设计的电子电路，监测和控制整个系统，相比于其他软启动系统的选择是昂贵的，但在转矩、负载均分和变速为主要考虑的场合,它又是一个可靠的，节约本钱的方式。DC电机一般使用在功率较大的输送装置上,包括需要输送带张力控制的多驱动系统和需要宽变速范围的输送装置上。1.2液力偶合器流体动力偶合器通常被称为液力偶合器，由三个根本单元组成：充当离心泵的叶轮,推进水压的涡轮和装进两个动力部件的外壳。流体从叶轮到涡轮，在从动轴产生扭矩。由于循环流体产生扭矩和速度，在驱动轴和从动轴之间不需要任何机械连接。这种连接产生的动力决定于液力偶合器的充液量，扭矩正比于输入速度。因在流体偶合中输出速度小于输入速度,其间的差值称为滑差,一般为1%～3%。传递功率可达几千千瓦。固定充液液力偶合器固定充液液力偶合器是在结构较简单和仅具有有限的弯曲局部的输送装置中最常用的软启动装置，其结构相比照拟简单，本钱又低，对现在使用的大多数输送机能提供优良的软启动效果。可变充液液力偶合器也称为限矩型液力偶合器。偶合器的叶轮装在AC电机上,涡轮装在从动减速器高速轴上，包含操作部件的轴箱安装在驱动基座。偶合器的旋转外壳有溢出口,允许液体不断地从工作腔中流出进入一个别离的辅助腔，油从辅助腔通过一个热交换器泵到控制偶合器充液量的电磁阀。为了控制单机传动系统的启动转矩,必须监测AC电机电流,给电磁阀的控制提供反应。可变充液液力偶合器可使用在中大功率输送系统中，功率可到达数千千瓦。这种驱动无论在机械,或在电气上都是很复杂的，其驱动系统本钱中等。勺管控制液力偶合器也称为调速型液力偶合器。此种液力偶合器同样由三个标准的液力偶合单元构成，即叶轮、涡轮和一个包含工作环路的外壳。此种液力偶合器需要在工作腔以外设置导管(也称勺管)和导管腔，依靠调节装置改变勺管开度(勺管顶端与旋转外壳间距)人为的改变工作腔的充液量,从而实现对输出转速的调节。这种控制提供了合理的平滑加速度，但其计算机控制系统很复杂。勺管控制液力偶合器可以应用在单机或多机驱动系统，功率范围为150kW～750kW。1．3变频控制(VFC)变频控制也是一种直接驱动方式，它具有非常独特的高性能。VFC装置为感应电机提供变化的频率和电压,产生优良的启动转矩和加速度。VFC设备是一个电力电子控制器,首先把AC整流成DC，然后利用逆变器，再将DC转换成频率、电压可控的AC。VFC驱动采用矢量控制或直接转矩控制(DTC)技术，能根据不同的负载采用不同的运行速度。VFC驱动能根据给定