ESAB Plasmarc EPP-450 - Fuses F1 and F2 Blown; Intermittent or Partial Operation

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Problem Possible Cause Action
FusesF1andF2blown.
Processcontrollerignitespilotarctoo
soon after providing the “Contactor
On”signal
Process controller must allow at least
300MS to lapse between the applica-
tion of the“Contactor On” signal and
theignitionofthepilotarc.Fixprocess
controllerlogicandreplacediodes.
Faultynegative(Electrode)outputcable
shortingtoearthground.
Repaircable
Shortedfreewheelingdiode.
Replace shorted freewheeling diode
andF1-F2
One or more shorted diode rectiers
(D13-D18)on“POSPlate”.
Replacealldioderectiersonthe“POS
P l a t e ”.
One or more shorted diode rectiers
(D7-D12)on“NEGPlate”.
Replacealldioderectiersonthe“NEG
P l a t e ”.
SECTION 6 TROUBLESHOOTING
6.3.7 Fuses F1 and F2 Blown
Problem Possible Cause Action
WorksOKat275Aorless-Over
current right side when cutting
over275A.LED6oncontrolboard
illuminated.
LooseorunpluggedconnectoratleftPWM/
DrivePCB(PCB2)
Secureconnector
FaultyleftPWM/DrivePCB
Replace right PWM / Drive PCB  P/N
0558038324
CheckvoltagebetweenP5-1andP5-2atthe
leftPWM/DrivePCB(PCB2).Shouldbe20V
AC.BetweenP5-1andP5-3shouldbe40VAC.
Ifnotthecontroltransformer(T5)isfaulty.
ReplacecontroltransformerT5
6.3.8 Intermittent, Interrupted or Partial Operation
NEVER attempt to power-up or operate the power source with any
Gate / Emitter IGBT Plug disconnected from it’s PWM / Gate Drive
Board. Attempting to operate the power source with any open (un-
plugged) IGBT Gate / Emitter Connector may damage the IGBT and
the plasma cutting torch.
CAUTION
WorksOKat275Aorless-Over
current left side when cutting
over275A.LED9oncontrolboard
illuminated.
LooseorunpluggedconnectoratRightPWM
/DrivePCB(PCB3)
Secureconnector
FaultyRightPWM/DrivePCB
Replace right PWM / Drive PCB  P/N
0558038324
CheckvoltagebetweenP5-1andP5-2atthe
rightPWM/DrivePCB(PCB3).Shouldbe20V
AC.BetweenP5-1andP5-3shouldbe40VAC.
Ifnotthecontroltransformer(T7)isfaulty.
ReplacecontroltransformerT7