Switch Boards And Main Transformer - Lincoln Electric POWER WAVE SVM156-A Service Manual

E-4
FIGURE E.3 - SWITCH BOARDS AND MAIN TRANSFORMER
POWER WAVE 455/R
CR1
SW1
INPUT
BOARD
CONTACTOR AND PRECHARGE
CONTROL SIGNALS FROM
CONTROL BOARD
2
FROM CONTROL
4
BOARD
V
AUX
A
RECONNECT
C
RELAY
115 VAC
52 VAC
T1
230 VAC
115 VAC
T2
SWITCH BOARDS AND MAIN
TRANSFORMER
There are two switch boards in the Power Wave 455/R
machine. Each contains an input capacitor and insu-
lated gate bipolar transistor (IGBT) switching circuitry.
Refer to Figure E.3. When the machine reconnect
switches are configured for a lower input voltage
(below 300VAC), the input capacitors are connected in
parallel. When the machine is configured for higher
input voltages (300VAC and above), the input capaci-
tors are connected in series.
When the input capacitors are fully charged, they act
as power supplies for the IGBT switching circuits. The
insulated gate bipolar transistors switch the DC power
from the input capacitors "on and off," thus supplying
pulsed DC current to the main transformer primary
windings. See IGBT OPERATION DISCUSSION AND
DIAGRAMS in this section.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
IGBT DRIVE
FROM
CONTROL
BOARD
CAP. V/F
FEEDBACK
LEFT
SWITCH
INPUT
BOARD
RECTIFIER
IGBT DRIVE
RECONNECT
FROM
CT CURRENT
SWITCH CONTROL
TO CONTROL
BOARD
BOARD
RIGHT
SWITCH
CAP. V/F
FEEDBACK
BOARD
67A
S1
VOLT
67B
SENSE
S6 VOLTAGE SENSE
BOARD
VOLTAGE SENSE SELECT
FEED
40 VDC
HEAD
BOARD
115 VAC
FAN
65 VDC
S6
DC
BUS BOARD
RECTIFIER
BUS
BOARD
40 VDC
WATER
40 VDC
COOLER
40 VDC
ARC LINK
115 VAC
WIRE
RECP.
S1
FEEDER
RECP.
POWER WAVE 455/R
MAIN
CT CURRENT
TO CONTROL
TRANSFORMER
BOARD
OUTPUT DIODES
D1 -D4
OUTPUT
DEVICE NET
S5
GATEWAY
CONNECTION
ARC LINK TO
BOARD
ROBOT
40 VDC
ARC LINK
+5V RS232
+5 V ARC LINK
CONNECTION
TO WIRE
POWER
+5V SPI
DRIVE
BOARD
+15V SPI
+5 V
+15 V
-15 V
+20 VDC
TO
CHOPPER
BOARD
LEFT CT
CURRENT
FB
Each switch board feeds current to a separate, oppo-
sitely wound primary winding in the Main Transformer.
The reverse directions of current flow through the main
transformer primaries, and the offset timing of the IGBT
switch boards induce an AC square wave output signal
at the secondary of the main transformer.
transformers located on the switch boards monitor the
primary currents.
abnormally high, the Control Board will shut off the
IGBTs, thus disabling the machine's output. The DC
current flow through each primary winding is clamped
back to each respective input capacitor when the
IGBTs are turned off. This is needed due to the induc-
tance of the transformer primary windings. The firing of
the two switch boards occurs during halves of a 50-
microsecond interval, creating a constant 20 KHZ out-
put.
ELECTRODE
TERMINAL
+20 VDC FROM
POWER BOARD
STT
CURRENT
ELECTRODE
STT CHOPPER TRANSDUCER
TERMINAL
BOARD
STT
DRIVE CURRENT
WORK
TRANSDUCER
OUTPUT
TERMINAL
CHOKE
C
U
R
S
R
T
TO
TO
E
T
RIGHT
LEFT
N
S.B.
S.B.
T
F
B
F
B
TO FAN RELAY
IGBT
DRIVES
CONTACTOR AND
PRECHARGE
CONTROL SIGNALS
THERMOSTATS
CONTROL
BOARD
S2 WORK
SENSE
S3
RS232
LEFT S.B.
CAP. V/F
RIGHT S.B.
CAP. V/F
RIGHT CT
CURRENT
FB
STATUS THERMAL
LIGHT LIGHT
If the primary currents become
E-4
+
+
Current