WTC MedWeld 3005, Operator'S Manual

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Danger!
DO NOT disable short detection (by setting
this parameter to DISABLE) for normal
operating conditions.
When disabling short detection, the control will
not shunt trip the circuit breaker in case of an
SCR short. The control will not detect situations
such as a catastrophic SCR failure. This can
cause tool damage, and create the potential
for serious injury or death.
When the processor detects no voltage drop across the SCRs
during four out of seven half-cycles, it examines the primary
current to determine whether the drop was due to a shorted SCR:
• Primary current exceeding a preset amperage indicates a
shorted SCR. The weld processor immediately generates a
SHORTED SCR fault.
• If the primary current is less than a preset amperage, the
processor checks the SCR Cycle Limit parameter to
determine whether the voltage drop was due to a shorted
SCR or shunting current.
• The SCR Cycle Limit parameter sets the maximum number of
consecutive cycles where a shorted SCR condition (without
current) can occur before the breaker is tripped. The control
then generates the appropriate fault (SHORTED SCR or
CURRENT SHUNTING fault).
WARNING!
If the control detects a shorted SCR condition
with current for four out of seven half-cycles,
the control will trip the breaker, regardless of
the programmed value of this setup parameter.
• If the control detects no primary current for 3 or more
consecutive cycles, it generates the WELDER CURRENT
SHUNTING fault. (If the SCR is shorted or current is
shunting, primary current will not be detected.) This fault
conditions indicates that shunting was detected for more
than 3 cycles but less than the number of cycles programmed
in the Shorted SCR Cycle Limit setup parameter.