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E-8 THEORY OF OPERATIONE-8
PROTECTION CIRCUITS
Protection circuits are designed into the PRECISION Tig 275 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 275 has the F.A.N. circuit feature, which means that the cooling fan will operate only while welding; then for about eight minutes after weld- ing 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 ini- tially 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. The output is limited to 350 amps.
PRECISION TIG 275
