Power Modules And Feedback - Lincoln Electric MULTI-WELD SVM151-A Service Manual

E-3
MULTI-WELD 350 BLOCK LOGIC DIAGRAM
INPUT
DIODES
ON/OFF
+
MODE
SWITCH
DC
(1/2)
POWER
SOURCE
(EXTERNAL)
_
POWER MODULES AND FEED-
BACK
The external DC source voltage is applied to parallel
capacitors incorporated within each of the two Power
(Chopper) Modules. These capacitors function as fil-
ters and 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 Board
through pulse width modulation gate signals.
Pulse Width Modulation in this section.
"chopped" DC output is applied through choke coils
and a shunt to the welding output terminals.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
FIGURE E.3 – POWER MODULES AND FEEDBACK
INPUT
CONTACTOR
CR1
INPUT
CAPACITORS
20
VDC
x 2
ANALOG
DC
40
VDC
CONTROL
BUS
POWER
POWER
SUPPLY
SUPPLY
BOARD
BOARD
PERIPHERAL
See
This
The
MULTI-WELD 350
LEFT AND RIGHT
CHOPPER MODULES
IGBT
FREEWHEELING DIODE
CHOPPER MODULE
CHOKE
IGBT FREEWHEELING DIODE
CHOPPER MODULE
ON/OFF
VOLTS
MODE
SWITCH
(1/2)
GATE
SIGNALS
WELD
REGULATED CONTROL
VOLTAGES
BOARD
FAN
40 VDC
ARC
OUTPUT
15 VDC
FORCE
CONTROL
CONTROL
CR1
COIL
BOARD
INPUT
INDICATOR
LIGHT
chokes function as current filters.
diodes are incorporated in the power circuit to provide
a current path for the stored energy in the chokes when
the IGBTs are turned off. See Chopper Technology in
this section.
Output voltage and current feedback information is fed
to the Weld Control Board. This information is sensed
from the output terminal circuits and the shunt. The
feedback information is processed by the Weld Control
Board, which regulates output voltage and current.
TO ELECTRODE
CABLE
+
SHUNT
CURRENT FEEDBACK
TO WELD CONTROL BOARD
AMPS
REMOTE
RECEPTACLE
CC SLOPE
(STICK/GOUGE or PIPE)
HOT
THERMAL
START
LIGHT
-
WORK
Free-wheeling
E-3