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PROTECTION CIRCUITS
Protection circuits are designed into the PRO-CUT 25
machine to sense trouble, damages, problems with
internal components, and to provide safety. These are
the main protection circuits:
OVERLOAD PROTECTION
The PRO-CUT 25 is electrically protected from
producing higher than normal output currents. If the
output current exceeds 25-30 amps, an electronic
protection circuit limits the current to within the
capabilities of the machine. A second circuit monitors
the input voltage and the voltage across the input filter
capacitors. If the input voltage or filter capacitor
voltage is too high, or too low, the protection circuit
will prevent machine output.
THERMAL PROTECTION
Three thermal protection devices protect the machine
from excessive operating temperatures. One device
is located on the output choke, one is located inside
the main transformer, and another is mounted on one
of the IGBT heat sinks. Excessive temperatures may
be caused by a lack of cooling air or by operating the
machine beyond the duty cycle and output rating. If
excessive operating temperatures should occur, the
thermal status indicator will turn on and the thermostat
will prevent output voltage or current. The thermal
protection devices are self-resetting once the machine
cools sufficiently. If the shutdown was caused by
excessive output or duty cycle and the fans are
operating normally, the power switch may be left on
and the reset should occur within a 15 minute period.
If the fan is not turning or the air intake louvers are
obstructed, the input power must be removed and the
fan problem or air obstruction must be corrected.
After a thermal overload occurs and the machine
resets, it may be necessary to activate the torch
trigger twice before a pilot arc will be initiated. This is
a safety precaution, to eliminate accidental pilot arc
initiation when the thermal protection self resets.
ACCIDENTAL OPERATION
PROTECTION
The PRO-CUT 25 has two protection circuits to
eliminate accidental pilot arc initiation. These two
circuits operate when the machine is first turned on
and after a thermal overload occurs. In these cases,
the first time the torch trigger is activated nothing will
happen. The torch trigger must be activated a second
time before pilot arc initiation occurs. This protection
is added in case the machine is turned on and the trig-
ger is already activated or if a thermal overload self
resets and the trigger is activated.
SAFETY PARTS-IN-PLACE
PROTECTION
The PRO-CUT 25 has protection circuits to detect the
proper connection of the torch and the proper
installation of the consumables. If an error is detected
with either of these two items, the Safety status LED
will be turned on and the output of the machine will be
disabled. The PRO-CUT 25 must be turned off and
the problem must be corrected before normal
operation can occur.
THEORY OF OPERATION
E-7 E-7
PRO-CUT 25
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