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SECTION 6 TROUBLESHOOTING

6.7 E-Stop (Emergency Stop) and Main Contactor (K1A, K1B and K1C) Circuits

Apower-upsequencetakesplacebeforetheMainContactor(K1)activates.K1isactuallythreeseparatecontactors–one

foreachprimaryinputphase.Thus,K1A,K1B,andK1CswitchphasesA,B,andCrespectivelytotheMainTransformer,T1.

Thepower-upsequencebeginswitharemoteContactorSignalactivatingK3andK33.Refertothedescriptionentitled,

Section6.6,AuxiliaryMainContactor(K3andK33)&SolidStateContactorCircuitsformoreinformation.K3andK33acti-

vatesK2closingthethreecontactsofK2.K2bypassesK1contactsprovidingprimaryinputpowertotheMainTransformer,

T1.ThiscurrentislimitedbythreeoneOhmresistors,R1,R2,andR3.Theresistorseliminatethehighsurgecurrentstypical

oftheturn-oninrushtransientsassociatedwithlargetransformers.ThehighcurrentsurgeofchargingtheBusCapacitor

BankisalsoeliminatedbyinitiallypoweringtheMainTransformerthroughK2andtheresistors.

ThedischargedBusCapacitorBankinitiallypreventstheoutputoftheMaintransformerfromreachingitsnormalvalue.

AstheBusCapacitorBankcharges,theMainTransformeroutputvoltagerisesandbecomeshighenoughforK1A,K1B,and

K1Ctoclose.OncetheK1’sareclosed,thecontactsoftheStartingContactor,K2,arebypassed,andfullprimarylinepower

issuppliedtotheMainTransformerthroughthecontactsoftheK1’s.

Becausethestartingsequencetakestime,itisimportantatleast300mSlapsebetweenapplyingtheContactorSignal

andapplyingloadtothepowersource.ApplyingloadtoosoonwillpreventtheK1’sfromclosingandfusesF1andF2will

open.

K15,theE-Stoprelaymustbeclosedforthepower-upsequencetotakeplace.K15containsonecontactintheK2coilcircuit

andanothercontactintheK1A,K1B,&K1Ccircuits.ThereisnopowersuppliedtotheMainTransformer,T1,untilK15isacti-

vated.ForK15toactivate,S5,theE-Stopswitchonthefrontpanelmustbeclosed.Also,thePlasmaControlmustcomplete

theE-stoploopbyclosinganisolatedcontactbetweenJ1-EandJ1-F.

TheE-StopswitchisclosedwhenevertheE-Stopbutton,onthefrontpanel,ispulledout.Fortroubleshootingpurposes

only,ajumpercanbeconnectedbetweenTB8-18andTB8-19.Ifajumperisinstalled,itMUSTberemovedbeforeplacing

thepowersourcebackintoservice.Ifthejumperisnotremoved,thepowersourceE-Stopconditionwillnotfunctionwhen

theE-StopbuttonforthePlasmaControlispushed.

J4-AandJ4-BareconnectedtogetherwhenevertheE-Stopbuttononthepowersourceispulledout.Thissignalcanbe

senttothePlasmaControlsothatthecontrolsensesthestateofthepowersourceE-Stopswitch.

ESAB Plasmarc EPP-450 User Manual

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