机械专业外文翻译(中英文翻译) (1).doc

机械专业外文翻译(中英文翻译) (1).doc

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第11页

外文翻译

英文原文

BeltConveyingSystemsDevelopmentofdrivingsystem

Amongthemethodsofmaterialconveyingemployed，beltconveyorsplayaveryimportantpartinthereliablecarryingofmaterialoverlongdistancesatcompetitivecost．Conveyorsystemshavebecomelargerandmorecomplexanddrivesystemshavealsobeengoingthroughaprocessofevolutionandwillcontinuetodoso．Nowadays，biggerbeltsrequiremorepowerandhavebroughttheneedforlargerindividualdrivesaswellasmultipledrivessuchas3drivesof750kWforonebelt（thisisthecasefortheconveyordrivesinChengzhuangMine）．Theabilitytocontroldriveaccelerationtorqueiscriticaltobeltconveyors’performance．Anefficientdrivesystemshouldbeabletoprovidesmooth，softstartswhilemaintainingbelttensionswithinthespecifiedsafelimits．Forloadsharingonmultipledrives．torqueandspeedcontrolarealsoimportantconsiderationsinthedrivesystem’sdesign.Duetotheadvancesinconveyordrivecontroltechnology，atpresentmanymorereliable．Cost-effectiveandperformance-drivenconveyordrivesystemscoveringawiderangeofpowerareavailableforcustomers’choices[1].

1Analysisonconveyordrivetechnologies

1．1Directdrives

Full-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．

1．2Hydrokineticcoupling

Hydrokineticcouplings，commonlyreferredtoa