E-8
E-8
PRECISION TIG 375
PROTECTION CIRCUITS
Protection circuits are designed into the Precision TIG
375 machine to sense trouble and shut down the
machine before the trouble damages internal machine
components. Both thermal protection and current over-
load are included.
FAN-AS-NEEDED (F.A.N.)
The Precision Tig 375 has the F.A.N. (fan as needed)
circuit feature, which means that the cooling fan will
operate only while welding; then for about eight min-
utes after welding has stopped to assure proper
machine cooling. This helps reduce the amount of dirt
and dust drawn into the machine along with the cooling
air. The cooling fan will operate briefly when the
machine power is initially turned on, and continuously
while the
yellow
Thermal shutdown light is lit.
THERMAL PROTECTION
This welder has thermostatic protection from excessive
duty cycles, overloads, loss of cooling and excessive
ambient temperatures. When the welder is subjected
to an overload, or inadequate cooling, the primary coil
thermostat and/or secondary coil thermostat will open.
This condition will be indicated by the illumination of
the
yellow
Thermal Shutdown light on the front panel.
The fan will continue to run to cool the power source.
Postflow occurs when Tig welding is shut down, but no
welding is possible until the machine is allowed to cool
and the
yellow
Thermal Shutdown light goes out. Once
the machine cools sufficiently, the thermostats are self-
resetting. If the shutdown is caused by excessive out-
put or duty cycle and the fan is operating normally, the
power may be left on and the reset should occur with-
in a 15 minute period. If the fan is not functioning prop-
erly or the air intake louvers are obstructed, the input
power must be removed and the fan problem or air
obstruction corrected.
OVERLOAD PROTECTION
The machine is electronically protected from producing
excessively high output currents.
THEORY OF OPERATION