Theory of operation, Switch boards – Lincoln Electric INVERTEC SVM129-B User Manual
Page 32
THEORY OF OPERATION
E-4
E-4
INVERTEC® STT® & STT® II
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
FIGURE E.4 – SWITCH BOARDS
SWITCH BOARDS
There are two switch boards in the INVERTEC® STT®
& STT® II, each containing an input filter capacitor.
The capacitors are connected in parallel when the
machine is connected for "low" input voltage. The
capacitors are connected in series when the reconnect
switch is configured for "high" input voltage. When the
capacitors are fully charged, they act as power sup-
plies for the switch boards. The switch boards contain
the Field Effect Transistors (FETs) which, when
switched on, supply the main transformer primary
windings with DC current flow. See Field Effect
Transistor (FET) Operation discussion and diagrams.
See Figure E.4.
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)