Lincoln Electric SP-250 Welding System User Manual


 
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E-5
THEORY OF OPERATION
E-5
IDEALARC SP-250
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.
THERMAL PROTECTION