THEORY OF OPERATION
E-4 E-4
POWER WAVE 655/R
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NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
SWITCH BOARDS AND MAIN
TRANSFORMER
There are two switch boards in the Power Wave 655/R
machine. Each contains two input capacitors and insu-
lated gate bipolar transistor (IGBT) switching circuitry.
Refer to Figure E.3. The input capacitors on each
board are connected in parallel. The two paralleled
pairs are then connected in series to accomodate the
high DC voltage from the rectifier.
When the input capacitors are fully charged, they act
as power supplies for the IGBT (insulated gate bipolar
transistors) switching circuits. The IGBTʼs 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 DISCUS-
SION AND DIAGRAMS in this section.
Each switch board feeds current to separate, opposite-
ly wound primary coils 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 monitor the primary currents. If the pri-
mary currents become abnormally high, the Control
Board will shut off the IGBTs, thus disabling the
machineʼs 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 inductance of the transformer pri-
mary windings. The firing of the two switch boards
occurs during halves of a 50-microsecond interval, cre-
ating a constant 20 KHZ output. See the PULSE
WIDTH MODULATION discussion in this section.
FIGURE E.3 - SWITCH BOARDS AND MAIN TRANSFORMER
+
INPUT
BOARD
LEFT
SWITCH
BOARD
RIGHT
SWITCH
BOARD
INPUT
RECTIFIER
CR1
GATEWAY
BOARD
DC
BUS
BOARD
FEED
HEAD
BOARD
POWER
BOARD
CONTROL
BOARD
OUTPUT
CHOKE
ELECTRODE
TERMINAL
THERMOSTATS
T1
T2
AUX
RECONNECT
RELAY
WATER
COOLER
115VAC
RECP.
115VAC
FAN
ARC LINK
WIRE
FEEDER
RECP.
S1
S6 CONNECTION
TOWIRE
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
115VAC
52VAC
230VAC
40VDC
40VDC
40VDC
40VDC
ARC LINK CONNECTION
TO
ROBOT
VOLTAGE SENSE
OUTPUT
CAP.V/F
FEEDBACK
CAP.V/F
FEEDBACK
IGBT DRIVE
FROM
CONTROL
BOARD
CT CURRENT
TO CONTROL
BOARD
-15V
+15V
+5V
+5V ARC LINK
+5V RS232
+15V SPI
STATUS THERMAL
LIGHT LIGHT
S2WORK
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
ARC LINK
IGBT
DRIVES
TO
LEFT
S.B.
TO
RIGHT
S.B.
67A
67B
SW1
BUS BOARD
RECTIFIER
CURRENT
TRANSDUCER
OUTPUT DIODES
D1 -D4
115VAC
40VDC
DEVICE NET
VOLTAGE SENSE SELECT
IGBT DRIVE
FROM
CONTROL
BOARD
+5V SPI
RIGHT CT
CURRENT
FB
TO FAN RELAY
CONTACTOR AND
PRECHARGE
CONTROL SIGNALS
65VDC
WORK
TERMINAL
POWER WAVE 655/R
380-
415
440-
460
550-
575
+
ETHERNET/
A
A
HARMONIC
FILTER
C
POS
NEG
Auxiliary
Fan