Theory of operation, Switch boards and main transformer, Power wave 455/r – Lincoln Electric POWER WAVE SVM173-A User Manual
Page 38
SWITCH BOARDS AND MAIN
TRANSFORMER
There are two switch boards in the Power Wave 455M
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.
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. Current
transformers located on the switch boards monitor the
primary currents. If the primary currents become
abnormally high, the Control Board will shut off the
IGBTs, thus disabling the machine’s output. The firing
of the two switch boards occurs during halves of a 50-
microsecond interval, creating a constant 20 KHZ out-
put.
E-4
E-4
THEORY OF OPERATION
POWER WAVE 455M/MSTT
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.3 - SWITCH BOARDS AND MAIN TRANSFORMER
+
+
INPUT
BOARD
RECONNECT
SWITCH
LEFT
SWITCH
BOARD
RIGHT
SWITCH
BOARD
INPUT
RECTIFIER
CR1
GATEWAY
BOARD
DC
BUS
BOARD
FEED
HEAD
BOARD
POWER
BOARD
CONTROL
BOARD
STT CHOPPER
BOARD
OUTPUT
CHOKE
STT
ELECTRODE
TERMINAL
ELECTRODE
TERMINAL
THERMOSTATS
T1
T2
AUX
RECONNECT
RELAY
WATER
COOLER
115 VAC
RECP.
115 VAC
FAN
ARC LINK
WIRE
FEEDER
RECP.
S1
S6
CONNECTION
TO WIRE
DRIVE
S1
S6
VOLT
SENSE
BOARD
MAIN
TRANSFORMER
S5
CONTACTOR AND PRECHARGE
CONTROL SIGNALS FROM
CONTROL BOARD
FROM CONTROL
BOARD
2
4
V
A
C
115 VAC
52 VAC
230 VAC
40 VDC
40 VDC
40 VDC
+20 VDC
TO
CHOPPER
BOARD
40 VDC
ARC LINK
CONNECTION
TO
ROBOT
VOLTAGE SENSE
OUTPUT
+20 VDC FROM
POWER BOARD
CT CURRENT
TO CONTROL
BOARD
CAP. V/F
FEEDBACK
CAP. V/F
FEEDBACK
IGBT DRIVE
FROM
CONTROL
BOARD
CT CURRENT
TO CONTROL
BOARD
-15 V
+15 V
+5 V
+5 V ARC LINK
+5V RS232
+15V SPI
STATUS THERMAL
LIGHT LIGHT
S2 WORK
SENSE
LEFT S.B.
CAP. V/F
RIGHT S.B.
CAP. V/F
S3
RS232
LEFT CT
CURRENT
FB
C
U
R
R
E
N
T
F
B
S
T
T
F
B
STT
DRIVE
ARC LINK
IGBT
DRIVES
TO
LEFT
S.B.
TO
RIGHT
S.B.
67A
67B
SW1
BUS BOARD
RECTIFIER
CURRENT
TRANSDUCER
CURRENT
TRANSDUCER
OUTPUT DIODES
D1 -D4
115 VAC
40 VDC
DEVICE NET
VOLTAGE SENSE SELECT
IGBT DRIVE
FROM
CONTROL
BOARD
+5V SPI
RIGHT CT
CURRENT
FB
TO FAN RELAY
CONTACTOR AND
PRECHARGE
CONTROL SIGNALS
65 VDC
WORK
TERMINAL
POWER WAVE 455/R