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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
ENGINE ROTOR
STATOR
AUXILIARY WINDINGS
W
E
L
D
W
I
N
D
I
N
G
MECHANICAL
ROTAT I ON
STARTER
ALTERNATOR
ENGINE
SENSORS
OUTPUT PROCESS/RANGE
1
2
0
V
A
C
120VAC
RECEPTACLES (2)
240VAC
RECEPTACLE
SLIP
RINGS
ANALOG
POWER SUPPLY
BOARD
ARC
WELD
CONTROL
BOARD
CONTROL
CONTROL SELECTOR
PWM
SIGNALS (2)
VOLTMETER
AMMETER
BATTERY
S
H
U
T
D
O
W
N
I
D
L
E
R
PERIPHERAL
BOARD
BATTERY
BOARD
PULL
COIL
BOARD
SOL
SOL
TO
IDLE
HOLD
COIL
42 VAC TO 14 PIN AMPHENOL
THREE-PHASE
RECTIFIER
CHOKE
IGBT
WORK
TERMINAL
ELECTRODE
TERMINAL
+
+
SHUNT
F
E
E
D
B
A
C
K
____
POWER MODULES
(2)
TO WELD
CONTROL
BOARD
FOR WIRE FEEDER
COMMANDER 500
(2) (2)
80 VDC
(2)
20 VDC
THERMAL
LIGHT
TO WELD
CONTROL
BOARD
10
VDC
10
VDC
120
VDC
1/2
BATTERY
BD
RUN/STOP
SWITCH