Theory of operation – Lincoln Electric INVERTEC SVM129-B User Manual
Page 31
RECONNECT, PROTECTION
BOARD, RECTIFICATION AND
PRECHARGE
The reconnect panel allows the user to switch to low or
high input voltage to match the input line voltage. The
AC input voltage is rectified and applied to the driver
board. The driver board contains precharging circuitry
for safe charging of the input filter capacitors. Once the
capacitors are precharged, the input relays are ener-
gized, connecting full input power to the input filter
capacitors. The protection board monitors the capaci-
tors for voltage balance and/or overvoltage and will de-
energize the input relays and precharge circuitry if
either occurs. The machine output will be disabled.
THEORY OF OPERATION
E-3
E-3
INVERTEC® STT® & STT® II
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.3 – RECONNECT, PROTECTION BOARD, RECTIFICATION AND PRECHARGE
POSITIVE
OUTPUT
TERMINAL
TERMINAL
OUTPUT
NEGATIVE
CONTROL BOARD
IGBT
DRIVER
BOARD
P
O
W
E
R
B
O
A
R
D
FAN
TRANS
T1
TRANS
T4
S
W
I
T
C
H
B
O
A
R
D
S
W
I
T
C
H
B
O
A
R
D
R
E
C
O
N
N
E
C
T
P
R
O
T
E
C
T
I
O
N
INPUT
RECTIFIER
LINE
SWITCH
CR1
CR2
B
O
A
R
D
D
R
I
V
E
R
B
O
A
R
D
PRE -
CHARGE
PRE -
CHARGE
CHOKE
CURRENT
SENSOR
IGBT
MODULE
1 OHM
PEAK
CURRENT
METER
BACK-
METER
PEAK
CURRENT
CONTROL
BACK-
CONTROL
HOT
START
CONTROL
WIRE
SIZE
SWITCH
WIRE
TYPE
SWITCH
VOLTAGE
SENSING
RECEPTACLE
REMOTE
CONTROL
RECEPTACLE
WIRE
RECEPTACLE
FEEDER
R
E
M
O
T
E
P
R
O
T
E
C
T
I
O
N
B
O
A
R
D
CURRENT
TRANS
T3
MAIN
TRANSFORMER
T2
115
VAC
18
VAC
2
4
V
A
C
"A"
LEAD
15VDC
T
H
E
R
M
O
S
T
A
T
CURRENT FEEDBACK
42VAC
VOLTAGE FEEDBACK
10VAC AND 6VAC
D
R
I
V
E
S
I
G
N
A
L
36VAC
GUN TRIGGER
LESS THAN 1VDC
PWM SIGNAL
PULSE TRANSFORMER SIGNAL
GROUND
GROUND
FET
FET
FET
FET
CAP
CAP
TAILOUT
CONTROL
(STT II ONLY)