Theory of operation, Thermal protection – Lincoln Electric WIRE-MATIC 255 SVM 119-A Manuel d'utilisation

Page 48

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E-5

THEORY OF OPERATION

E-5

WIRE-MATIC 255

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 WIRE-
MATIC 255 machine. One of the thermostats, located
on the output choke, energizes the cooling fan motors
when required. The other choke thermostat "opens"
the trigger circuit, preventing machine weld output and
wire feed, if excessive operating temperatures are
detected. The third thermostat insures that the fan
motors are operating when required.

The thermostats are self-resetting once the machine
cools sufficiently. If 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

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

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