PROTECTIVE CIRCUITS
Protective circuits are designed into the Square Wave
TIG 355 to sense trouble and shut down the machine
before the trouble damages the internal machine com-
ponents. Both thermal protection and current over-
load are included.
THERMAL PROTECTION
Thermostats protect the machine from excessive
operating temperatures. Excessive operating temper-
atures may be caused by a lack of cooling air or by
operating the machine beyond the duty cycle and out-
put rating. If excessive operating temperature should
occur, causing the secondary thermostat to open, the
input contactor will shut the machine off. If the prima-
ry thermostat opens, the machine will stay on (pilot
light, meters and fans running), but output current will
be limited to no more than 5 amps.
Once the machine cools sufficiently the thermostats
are self-resetting. If the thermostat shutdown is
caused by excessive output or duty cycle and the fan
is operating normally, the power may be left on, and
the reset should occur within a 15 minute period. If the
fan is not functioning properly or the air intake louvers
are obstructed, then the input power must be removed
and the fan problem or air obstruction corrected.
OVERLOAD PROTECTION
The machine is electronically protected from produc-
ing excessively high output currents. Should the out-
put current exceed approximately 400 amps, an elec-
tronic circuit will reduce and limit the output current.
The machine will continue to limit the output current
until the overload is removed.
THEORY OF OPERATION
E-8
E-8
SQUARE WAVE TIG 355
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