ESAB Precision Plasmarc EPP-450 Manuel D'instructions page 46

section 6
6.3.7 fuses f1 and f2 blown
problem
Fuses F1 and F2 blown.
6.3.8 intermittent, interrupted or partial operation
problem
Works OK at 275A or less - Over
current right side when cutting
over 275A. LED 6 on control board
illuminated.
Works OK at 275A or less - Over
current left side when cutting
over 275A. LED 9 on control board
illuminated.
caution
possible cause
Process controller ignites pilot arc too
soon after providing the "Contactor
On" signal
Faulty negative (Electrode) output cable
shorting to earth ground.
Shorted freewheeling diode.
One or more shorted diode rectifiers
(D13-D18) on "POS Plate".
One or more shorted diode rectifiers
(D7-D12) on "NEG Plate".
possible cause
Loose or unplugged connector at left PWM /
Drive PCB (PCB2)
Faulty left PWM / Drive PCB
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.
Loose or unplugged connector at Right PWM
/ Drive PCB (PCB3)
Faulty Right PWM / Drive PCB
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.
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.
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.
Repair cable
Replace shorted freewheeling diode
and F1-F2
Replace all diode rectifiers on the "POS
Plate".
Replace all diode rectifiers on the "NEG
Plate".
Secure connector
Replace right PWM / Drive PCB P/N
0558038324
Replace control transformer T5
Secure connector
Replace right PWM / Drive PCB P/N
0558038324
Replace control transformer T7
46
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