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外文翻译--带传动设计.doc

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外文翻译--带传动设计.doc

英文译文tapetransportAmongthemethodsofmaterialconveyingquantity,beltconveyorsplayaveryimportantpartinthereliablecarryingofmaterialoverlongdistancesatcompetitivecost.Conveyorsystemshavebecomelargerandmorecomplexanddrivesystemshavealsobeengoingthroughaprocessofevolutionandwillcontinuetodoso.Nowadays,biggerbeltsrequiremorepowerandhavebroughttheneedforlargerindividualdrivesaswellasmultipledrivessuchas3drivesof750kWforonebeltthisisthecasefortheconveyordrivesinChengzhuangMine.Theabilitytocontroldriveaccelerationtorqueiscriticaltobeltconveyorsperformance.Aefficientdrivesystemshouldbeabletoprovidesmooth,softstartswhilemaintainingbelttensionswithinthespecifiedsafelimits.Forloadsharingonmultipledrives.torqueandspeedcontrolarealsoconsiderationsinthedrivesystemsdesign.Duetotheadvancesinconveyordrivecontroltechnology,atpresentmanymorereliable.Costeffectiveandperformancedrivenconveyordrivesystemscoveringawiderangeofpowerareavailableforcustomerschoices1.1tapetransportonconveyordrivetechnologies1.1ThebelttransmissionmodeFullvoltagestarters.Withafullvoltagestarterdesign,theconveyorheadshaftisdirectcoupledtothemotorthroughthegeardrive.Directfullvoltagestartersareadequateforrelativelylowpower,simpleProfileconveyors.Withdirectfullvoltagestarters.nocontrolisprovidedforvariousconveyorloadsand.dependingontheratiobetweenfullandnoloadpowerrequirements,emptystartingtimescanbethreeorfourtimesfasterthanfullload.Themaintenancefreestartingsystemissimple,lowcostandveryreliable.However,theycannotcontrolstartingtorqueandmaximumstalltorquetherefore.theyarelimitedtothelowpower,simpleprofileconveyorbeltdrives.Reducedvoltagestarters.Asconveyorpowerrequirementsincrease,controllingtheappliedmotortorqueduringtheaccelerationperiodbecomesincreasinglyimportant.Becausemotortorqueisafunctionofvoltage,motorvoltagemustbecontrolled.ThiscanbeachievedthroughreducedvoltagestartersbyemployingasiliconcontrolledrectifierSCR.AcommonstartingmethodwithSCRreducedvoltagestartersistoapplylowvoltageinitiallytotakeupconveyorbeltslack.andthentoapplyatimedlinearrampuptofullvoltageandbeltspeed.However,thisstartingmethodwillnotproduceconstantconveyorbeltacceleration.Whenaccelerationiscomplete.theSCRs,whichcontroltheappliedvoltagetotheelectricmotor.arelockedinfullconduction,providingfulllinevoltagetothemotor.Motorswithhighertorqueandpullvptorque,canprovidebetterstartingtorquewhencombinedwiththeSCRstarters,whichareavailableinsizesupto750KW.Woundrotorinductionmotors.WoundrotorinductionmotorsareconnecteddirectlytothedrivesystemreducerandareamodifiedconfigurationofastandardACinductionmotor.Byinsertingresistanceinserieswiththemotorsrotorwindings.themodifiedmotorcontrolSystemcontrolsmotortorque.Forconveyorstarting,resistanceisplacedinserieswiththerotorforlowinitialtorque.Astheconveyoraccelerates,theresistanceisreducedslowlytomaintainaconstantaccelerationtorque.Onmultipledrivesystems.anexternalslipresistormaybeleftinserieswiththerotorwindingstoaidinloadsharing.themotorsystemshavearelativelysimpleadesign.However,thecontrolsystemsforthesecanbehighlycomplex,becausetheyarebasedoncomputercontroloftheresistanceswitching.Today,themajorityofcontrolsystemsarecustomdesignedtomeetaconveyorsystemsparticularspecifications.Woundrotormotorsareappropriateforsystemsrequiringmorethan400KW.DCmotor.DCmotors.availablefromafractionofthousandsofKW,aredesignedtodeliverconstanttorquebelowbasespeedandconstantKWabovebasespeedtothemaximumallowablerevolutionsperminuter/min.withthemajorityofconveyordrives,a.DCshuntwoundmotorisused.Whereinthemotorsrotatingarmatureisconnectedexternally.ThemostcommontechnologyforcontrollingDCdrivesisaSCRdevice.whichallowsforcontinualvariablespeedoperation.TheDCdrivesystemismechanicallysimple,butcanincludecomplexcustomdesignedelectronicstomonitorandcontrolthecompletesystem.thissystemoptionisexpensiveincomparisontoothersoftstartsystems.butitisareliable,costeffectivedriveinapplicationsinwhichtorque,loadsharingandvariablespeedareprimaryconsiderations.DCmotorsgenerallyareusedwithhigherpowerconveyors,includingcomplexprofileconveyorswithmultipledrivesystems,boostertrippersystemsneedingbelttensioncontrolandconveyorsrequiringawidevariablespeedrange.1.2HydrokineticcouplingHydrokineticcouplings,commonlyreferredtoasfluidcouplings.arecomposedofthreebasicelementsthedrivenimpeller,whichactsasacentrifugalpumpthedrivinghydraulicturbineknownastherunnerandacasingthatenclosesthetwopowercomponents.Hydraulicfluidispumpedfromthedrivenimpellertothedrivingrunner,producingtorqueatthedrivenshaft.Becausecirculatinghydraulicfluidproducesthetorqueandspeed,nomechanicalconnectionisrequiredbetweenthedrivinganddrivershafts.Thepowerproducedbythiscouplingisbasedonthecirculatedfluidsamountanddensityandthetorqueinproportiontoinputspeed.Becausethepumpingactionwithinthefluidcouplingdependsoncentrifugalforces.theoutputspeedislessthantheinputspeed.Referredtoasslip.thisnormallyisbetween1and3.BasichydrokineticcouplingsareavailableinconfigurationsfromfractionaltoseveralthousandKW.Fixedfillfluidcouplings.Fixedfillfluidcouplingsarethemostcommonlyusedsoftstartdevicesforconveyorswithsimplerbeltprofilesandlimitedconvex/concavesections.Theyarerelativelysimple,lowcost,reliable,maintenancefreedevicesthatprovideexcellentsoftstartingresultstothemajorityofbeltconveyorsinusetoday.Variablefilldraincouplings.Drainablefluidcouplingsworkonthesameprincipleasfixedfillcouplings.ThecouplingsimpellersaremountedontheACmotorandtherunnersonthedrivenreducerhighspeedshaft.Housingmountedtothedrivebaseenclosestheworkingcircuit.Thecouplingsrotatingcasingcontainsbleedofforificesthatcontinuallyallowfluidtoexittheworkingcircuitintoaseparatehydraulicreservoir.Oilfromthereservoirispumpedthroughaheatexchangertoasolenoidoperatedhydraulicvalvethatcontrolsthefillingofthefluidcoupling.Tocontrolthestartingtorqueofasingledriveconveyorsystem,theACmotorcurrentmustbemonitoredtoprovidefeedbacktothesolenoidcontrolvalve.Variablefilldraincouplingsareusedinmediumtohighkwconveyorsystemsandareavailableinsizesuptothousandsofkw.Thedrivescanbemechanicallycomplexanddependingonthecontrolparameters.thesystemcanbeelectronicallyintricate.Thedrivesystemcostismediumtohigh,dependinguponsizespecified.Hydrokineticscoopcontroldrive.Thescoopcontrolfluidcouplingconsistsofthethreestandardfluidcouplingcomponentsadrivenimpeller,adrivingrunnerandacasingthatenclosestheworkingcircuit.Thecasingisfittedwithfixedorificesthatbleedapredeterminedamountoffluidintoareservoir.Whenthescooptubeisfullyextendedintothereservoir,thecouplingis100percentfilled.Thescooptube,extendingoutsidethefluidcoupling,ispositionedusinganelectricactuatortoengagethetubefromthefullyretractedtothefullyengagedposition.Thiscontrolprovidesreasonablysmoothaccelerationrates.tobutthecomputerbasedcontrolsystemisverycomplex.Scoopcontrolcouplingsareappliedonconveyorsrequiringsingleormultipledrivesfrom150KWto750KW.1.3VariablefrequencycontrolVFCVariablefrequencycontrolisalsooneofthedirectdrivemethods.theemphasizingdiscussionaboutithereisbecausethatithassouniquecharacteristicandsogoodperformancecomparedwithotherdrivingmethodsforbeltconveyor.VFCdevicesProvidevariablefrequencyandvoltagetotheinductionmotor,resultinginanexcellentstartingtorqueandaccelerationrateforbeltconveyordrives.VFCdrives.availablefromfractionaltoseveralthousandkW,areelectroniccontrollersthatrectifyAClinepowertoDCand,throughaninverter,convertDCbacktoACwithfrequencyandvoltagecontrol.VFCdrivesadoptvectorcontrolordirecttorquecontrolDTCtechnology,andcanadoptdifferentoperatingspeedsaccordingtodifferentloads.VFCdrivescanmakestartingorstallingaccordingtoanygivenScurvesrealizingtheautomatictrackforstartingorstallingcurves.VFCdrivesprovideexcellentspeedandtorquecontrolforstartingconveyorbelts.andcanalsobedesignedtoprovideloadsharingformultipledrives.easilyVFCcontrollersarefrequentlyinstalledonlowerpoweredconveyordrives,butwhenusedattherangeofmediumhighvoltageinthepast.thestructureofVFCcontrollersbecomesvery

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