Main Transformer - Lincoln Electric PRO-CUT 25 SVM149-A Service Manual

E-4
SW1
L1 RL3
A
300uH R1
10/10W
B
V1
115VAC
L1
V2
230V
RL1
115V
L1
Input
Voltage Board
12VDC
Air
Purge
Solenoid
Switch
1

MAIN TRANSFORMER

The pair of IGBTs act as a switch assembly. This
assembly feeds a primary winding of the main trans-
former. When current is pulsed through this primary
winding, a resultant current is produced on the sec-
ondary winding of the main transformer. The DC cur-
rent flow through the primary winding is redirected or
"clamped" back to the filter capacitors when the IGBTs
are turned off. This is needed due to the inductance of
the transformer primary winding.
The primary current also passes through the current
transformer, which sends a signal to the control cir-
cuits of the inverter board. This signal and the control
circuits limit the maximum primary current flow
through the IGBTs. The pair of IGBT's are fired at 15
microsecond intervals, creating a constant 66.6KHz
output.
THEORY OF OPERATION
FIGURE E.4 – MAIN TRANSFORMER
AC
RL2 AC
CP CP
RL2
CP
CP
CP
RL2
AC
AC
RL1
RL2
T1
CN1 CN2
15VAC
1 9
15VAC
2 10
SAFETY
3 5
+28VDC
4 6
SEC GND
5
3
OVLOAD
6 22
115/230
7 2
+12VDC
8
20
15 16
8 6 17 9 3
CN1
Display LED's
Control Board
PRO-CUT 25
Q1a,b,c
IRG4BC30W
C26
T2
PRI
+
R1
C1a,b
C12
CP
+
R2
C2a,b
Q2a,b,c
IRG4BC30W
C13
Main Inverter Board
CN1
12 18 14 1 11 4 13 7 19 24 21 23 8 17 1 2 3 4
1 2 18 14 7 15 4 11 5 16 10 12 13 23 22 24
Output Control
The secondary portion of the main transformer is made
up of one winding.
electrode-to-nozzle and electrode-to-work voltages
and the resulting currents. This high current winding is
capable of supplying maximum output current during
the cutting process. The output current is regulated
via pulse width modulation. The control circuitry, on
the inverter board, receives a signal from the control
board and regulates the output current to the desired
level.
WORK CLAMP
Lout
D10
BS1
WRK
240uH
8A
+12VDC TRANSFER
SEC
D11
RL1 NZL (2)
C14
R24
6.8k/5W
SHUNT
EL (3)
SH- SH+
CN3
1
2
3
4
This winding supplies the
E-4
PT
12VDC