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.
