AC WELDING OUTPUT
Rotating the polarity switch to the AC position changes
the welding power circuit. One lead (X1) of the main
transformer secondary is connected to the machine’s
output work terminal. The other secondary lead (X2) is
connected to one of the AC connections of the SCR
bridge. The electrode terminal is connected to the
other AC side of the bridge. The choke is now electri-
cally across the negative and positive SCR bridge con-
nections. With the ability of the choke to store energy
and the SCRs to turn on at the appropriate times, an
AC square wave is developed and applied to the out-
put terminals.
THEORY OF OPERATION
E-6 E-6
SQUARE WAVE TIG 275
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FIGURE E.7 – AC WELDING OUTPUT
FIGURE E.8 – AC SQUARE WAVE WELDING CURRENT GENERATION
