Lincoln Electric POWER MIG SVM157-A Service Manual page 33

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PROTECTIVE DEVICES AND CIRCUITS
THERMAL AND OVERLOAD PROTECTION
The POWER MIG 200 has two built-in protective
thermostats that respond to excessive temperatures.
One is located on the main transformer.
thermostat is located on the output rectifier heat sink
assembly. They open the wire feed and welder
output circuits if the machine exceeds the maximum
safe operating temperature. This can be caused by
a frequent overload or high ambient temperature.
The thermostats are self-resetting once the machine
cools sufficiently. If the thermostat shutdown is caused
by excessive output or duty cycle and the fan is
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 louver are
obstructed, then the input power must be removed
and the fan problem or air obstruction must be
corrected.
THEORY OF OPERATION
WIREFEED OVERLOAD PROTECTION
The POWER MIG 200 has solid state overload
protection of the wire drive motor.
becomes overloaded, the protection circuitry turns off
The other
the wire feed speed and gas solenoid.
proper size tip liner, drive rolls, and any obstructions
or bends in the gun cable.
factors that would impede the wire feeding.
resume welding, simply pull the trigger. There is no
circuit breaker to reset, as the protection is done with
reliable solid state electronics.
POWER MIG 200
E-5
If the motor
Check for
Check for any other
To