Lincoln Electric SVM146-A Protection Circuits, Overload Protection, Thermal Protection

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THEORY OF OPERATION

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PROTECTION CIRCUITS

Protection circuits are designed into the PRO-CUT 80 machine to sense trouble and shut down the machine before the trouble damages internal machine compo- nents. Both overload and thermal protection circuits are included.

OVERLOAD PROTECTION

The PRO-CUT 80 is electrically protected from pro- ducing higher than normal output currents. If the out- put current exceeds 85-90 amps, an electronic pro- tection circuit limits the current to within the capabili- ties of the machine.

Another protection circuit monitors the voltage across the input filter capacitors. If the filter capacitor voltage is too high, too low or not balanced the protection cir- cuit may prevent machine output.

THERMAL PROTECTION

Two thermostats protect the machine from excessive operating temperatures. One thermostat is located on the output choke and the other on the power board IGBT heat sink. 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 light and the thermostat will prevent output voltage or current.

Thermostats are self-resetting once the machine cools sufficiently. If the thermostat shutdown was caused by excessive output or duty cycle and the fan is oper- ating 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.

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PRO-CUT 80