B-6B-6 OPERATION

FAN CONTROL

The fan is designed to come on automatically when a
weld arc is established. The fan will stay on for a mini-
mum of 6 minutes after the weld arc is terminated.
The fan will also stay on when the machine’s welding
and feeding are disabled during thermostatic over
temperature protection. (See Welding Thermal
Overload Protection)

INPUT LINE VOLTAGE PROTECTION

High Line Voltage — If the line voltage exceeds
125% of rated input voltage, the output will be
reduced to the lower level to protect voltage rating of
the capacitor bank.
Low Line Voltage — You may not be able to get
maximum output from the machine if the line voltage
is less than rated input. The unit will continue to weld,
but the output may be less than what is set.

WIRE FEED OVERLOAD

PROTECTION

The PM 255 has solid state overload protection of the
wire drive motor. If the motor becomes overloaded,
the protection circuitry turns off the wire feed speed
and gas solenoid. Check for proper size tip, liner, and
drive rolls, for any obstructions or bends in the gun
cable, and any other factors that would impede the
wire feeding. to resume welding, simply pull the trig-
ger. There is no circuit breaker to reset, as the protec-
tion is done with reliable solid state electronics.

WELDING THERMAL OVERLOAD

PROTECTION

The PM 255 has built-in protective thermostats that
respond to excessive temperature. They open the
wire feed and welder output circuits if the machine
exceeds the maximum safe operating temperature
because of a frequent overload, or high ambient tem-
perature plus overload. The thermostats automatically
reset when the temperature reaches a safe operating
level and welding and feeding are allowed again,
when gun is retriggered.

OVERCURRENT PROTECTION

The machine will automatically reduce the output if the
load on the machine exceeds 300 to 320 amperes.
This protects the welding power SCR’s from exces-
sive short circuit currents and from exceeding their
temperature rating before the thermostats can react.
Welding Procedure Information
Note: See inside cover of machine for additional, commonly used welding procedure information.
PM 255