WELD WINDINGS, RECTIFIER,
POWER MODULES AND
FEEDBACK
The three-phase stator weld windings are connected to
a three-phase rectifier bridge. The resultant DC volt-
age is applied to four paralleled capacitors incorporat-
ed within each of the two power modules. There are
two capacitors in each module. These capacitors func-
tion as filters and also as power supplies for the IGBTs.
See IGBT Operation in this section. The IGBTs act as
high-speed switches operating at 20KHZ. These
devices are switched on and off by the Weld Control
PC board through pulse width modulation circuitry.
See Pulse Width Modulation in this section. This
"chopped" DC output is applied through choke coils
and a shunt to the welding output terminals. The choke
functions as a current filter, and it helps to balance the
outputs of the two power modules. Free-wheeling
diodes are incorporated in the power modules to pro-
vide a current path for the stored energy in the choke
when the IGBTs are turned off. See Chopper
Technology in this section.
Output voltage and current feedback information is fed
to the Weld Control PC board. This information is
sensed from the output terminal circuits and the shunt.
E-3 E-3
THEORY OF OPERATION
COMMANDER 500
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NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.3 - WELD WINDINGS, RECTIFIER, POWER MODULES AND FEEDBACK
