Filter
Top Products
GENERAL DESCRIPTION
The Invertec STT is a 225 ampere, inverter based, arc
welding power supply specifically designed for the
Surface Tension Transfer (STT) welding process. It
cannot be classified as either a constant current (CC)
or a constant voltage (CV) machine. The STT pro-
duces current of a desired waveform to reduce spatter
and fumes. The STT process is optimized for short -
circuit GMAW welding only.
INPUT VOLTAGE
The Invertec STT can be connected for a variety of
three-phase voltages. The initial input power is applied
to the STT through a line switch located on the front of
the machine. The AC input voltage is applied to the
input rectifier and the T1 auxiliary transformer. The T1
transformer develops the appropriate AC voltages to
operate the cooling fan, the power and control boards.
The T1 transformer also supplies primary voltage to the
T4 auxiliary transformer as well as 42 VAC to an exter-
nal wire feeder. The T4 transformer supplies power to
the IGBT drive board and the control board.
THEORY OF OPERATION
E-2 E-2
INVERTEC STT
Return to Section TOC Return to Section TOC Return to Section TOC Return to Section TOC
Return to Master TOC Return to Master TOC Return to Master TOC Return to Master TOC
FIGURE E.2 – INPUT VOLTAGE
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
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
RECEPTACL
E
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)