Lincoln Electric service manual Thermal Protection, Idealarc SP-250

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E-5 THEORY OF OPERATION E-5

THERMAL PROTECTION

A thermostat protects the machine from excessive operating temperatures.. Excessive operating temper- atures may be caused by a lack of cooling air or oper- ating the machine beyond the duty cycle and output rating. There are three thermostats within the SP-250 machine. One of the thermostats, located on the out- put choke, energizes the cooling fan motors when required. The other choke thermostat "opens" the trig- ger circuit, preventing machine weld output and wire feed, if excessive operating temperatures are detect- ed. The third thermostat insures that the fan motors are operating when required.

The thermostats are self-resetting once the machine cools sufficiently. It the thermostat shutdown is 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 fans are not turning or the air intake louvers are obstructed, then the input power must be removed and the fan problem or air obstruction be corrected.

IDEALARC SP-250