CDBrakiss1

UserGuideBrakingUnitsForCDandCDLDrivesSafetyInformationPersonssupervisingandperformingtheelectricalinstallationormaintenanceofaDriveand/oritsexternalOptionUnitmustbesuitablyqualifiedandcompetentintheseduties.TheyshouldbegiventheopportunitytostudyandifnecessarytodiscussthisUserGuidebeforeworkisstarted.ThevoltagespresentintheDriveandexternalOptionUnitsarecapableofinflictingasevereelectricshockandmaybelethal.TheStopfunctionoftheDrivedoesnotremovedangerousvoltagesfromtheterminalsoftheDriveandexternalOptionUnit.Mainssuppliesshouldberemovedbeforeanyservicingworkisperformed.Theinstallationinstructionsshouldbeadheredto.Anyquestionsordoubtshouldbereferredtothesupplieroftheequipment.ItistheresponsibilityoftheownerorusertoensurethattheinstallationoftheDriveandexternalOptionUnit,andthewayinwhichtheyareoperatedandmaintainedcomplieswiththerequirementsoftheHealthandSafetyatWorkActintheUnitedKingdomandapplicablelegislationandregulationsandcodesofpracticeintheUKorelsewhere.TheDrivesoftwaremayincorporateanoptionalAuto-startfacility.Inordertopreventtheriskofinjurytopersonnelworkingonornearthemotororitsdrivenequipmentandtopreventpotentialdamagetoequipment,usersandoperators,allnecessaryprecautionsmustbetakenifoperatingtheDriveinthismode.TheStopandStartinputsoftheDriveshouldnotbereliedupontoensuresafetyofpersonnel.IfasafetyhazardcouldexistfromunexpectedstartingoftheDrive,aninterlockshouldbeinstalledtopreventthemotorbeinginadvertentlystarted.GeneralInformationThemanufactureracceptsnoliabilityforanyconsequencesresultingfrominappropriate,negligentorincorrectinstallationoradjustmentoftheoptionaloperatingparametersoftheequipmentorfrommismatchingtheDrivewiththemotor.ThecontentsofthisUserGuidearebelievedtobecorrectatthetimeofprinting.Intheinterestsofacommitmenttoapolicyofcontinuousdevelopmentandimprovement,themanufacturerreservestherighttochangethespecificationoftheproductoritsperformance,orthecontentsoftheUserGuide,withoutnotice.Allrightsreserved.NopartofthisUserGuidemaybereproducedortransmittedinanyformorbyanymeans,electricalormechanicalincludingphotocopying,recordingorbyanyinformationstorageorretrievalsystem,withoutpermissioninwritingfromthepublisher.Copyright©November1994ControlTechniquesDrivesLtdPartNumber:0412-0001IssueCode:BCNU1IssueDate:November1994ContentsIntroduction1Description2Data2MechanicalInstallation5ElectricalInstallation5Sizingofexternalbrakingresistor11OperatingProcedures12Diagnostics13BrakingUnitsforCDandCDLDrives1IntroductionWhenaVariableSpeedDrivedeceleratesamotor,themotorreturnspowertotheDrive.TheregeneratedpowercanbedissipatedonlywithintheDrive;itcannotbereturnedtotheACpower.IftheregeneratedpowerismorethantheinternallossesoftheDrive,thevoltageontheinternalDCbuswillrisetoalevelthatmaycausetheDrivetotriponover-voltage.TypicallyaDrivecandissipateinternallyabout3%ofitsratedpower.Iftheregeneratedpowershouldexceedthis,anoptionalbrakingunitisrequired.Whetherornotanoptionalbrakingunitisused,thecurrentratingoftheDrivewilldeterminethemaximumamountofregeneratedcurrentthatcanbeaccepted.Iftheregeneratedcurrentexceeds150%ofthecurrentratingoftheDrive,theDrivewilltriponover-current.Influencesonregeneratedpowerareasfollows:•Theinertiaofthemotorandload•Themaximumspeedofthemotorandload•Therequireddecelerationrate•ThedecelerationmodesetbyDriveparametersb2andb7•PowerratingoftheDrive•CurrentratingoftheDriveFromtheory,theamountofregeneratedpowerPforaconstantrateofdecelerationa,agiveninertiaI,andatacertainspeedsis:P=asIwhere:P=wattsa=radianspersec2s=radianspersecI=kg.m2ForaDrivewithagivendecelerationrate(setinPr3orPr40toPr46)andacertainspeedinHz,theaboveequationbecomes:[]PIpt=⎛⎝⎜⎞⎠⎟×120412ϖπwhere:ωω=speedinHzoftheDrivep=numberofmachinepoles(eg.2,4,-etc)t=decelerationtimesetinPr3orPr40to46for120Hzmaximumfrequency.(Ifb14setforupperlimitfrequencyotherthan120Hz,modifyconstantof120tocorrectupperlimitfrequency.)Fromtheaboveequationitcanbeseenthattheregenerativepowerisdirectlydependentonthemachine/loadinertiaandthespeedofoperationoftheDrive.ThelowerthevalueofPr3,thegreatertheregenerativepowerbyvirtueoftheinverserelationship.Thisequationthereforeexplainsthefirstthreeofthefactorswhichinfluencetheregenerativepower.Theinfluenceofthesettingsforb2andb7hasonlyasmallinfluenceontheregenerativepowerproducedduringdeceleration.ItmustbenotedthatregenerationwilloccurwheneverthespeedoftheDriveisreduced,whetherornottheDriveisstopping.Theconsequencesofthesettingsofb2andb7(describedbelow)arevalidforallspeedreductions.BrakingUnitsforCDandCDLDrives2Whenb2andb7arebothzero,theinternalrampisstoppedwhenevertheDCbusvoltageintheDriveexceedsthemaximumallowableincreaseabovethenormalworkingvalue.Thisisthelevelatwhichthebrakingunitswitchesinthebrakingresistor.ThismodeofoperationextendsthedecelerationramptoreducethelikelihoodoftheDrivetrippingonover-voltage.AstheDCbusvoltagerises,thevoltageappliedtothemotorincreasesproportionally.Thishastheaddedconsequenceofincreasingthemagnetizingcurrentofthemotorwhich,inturn,increasesthedissipationcapabilityofthemotorandDriveforregenerat