Precharge And Protection - Lincoln Electric PRO-CUT 25 SVM149-A Service Manual

E-3
SW1
L1 RL3
A
300uH R1
10/10W
B
RL2
V1
115VAC
L1
V2
T1
230V
RL1
115V
L1
Input
Voltage Board
12VDC
Air
Purge
Solenoid
Switch
1

PRECHARGE AND PROTECTION

The input voltage is rectified by the input rectifier on
the inverter board. The resultant DC voltage is applied
to the filter capacitors through the automatic
reconnect of the input board. The input board also
contains precharging circuitry for the safe charging of
the input filter capacitors. Once the capacitors are
precharged the input board activates the RL3 input
relay. This connects full input power to the filter
capacitors. When the filter capacitors are fully
charged they act as power supplies for the IGBT
switching circuit. The IGBTs supply the main trans-
former primary winding with DC current flow.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
FIGURE E.3 – PRECHARGE AND PROTECTION
AC
AC
RL2
CP CP
RL2
CP
CP
CP
RL2
AC
AC
RL1
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
12 18 14 1 11 4 13 7 19 24 21 23 8
8 6 17 9 3 1 2 18 14 7 15 4 11 5 16 10 12 13
CN1
Display LED's
Control Board
PRO-CUT 25
Q1a,b,c
D10
IRG4BC30W
C26
T2
PRI SEC
+
R1
C1a,b
D11
C12
CP
+
R2
C2a,b
Q2a,b,c
IRG4BC30W
C13
Main Inverter Board
CN1
17 1 2 3 4
23 22 24
Output Control
The inverter board also monitors the filter capacitors
for overvoltage. If this occurs, the appropriate signal
is sent to the control board to disable the machines
output and to turn on the Thermal/Voltage Overload
status LED. See IGBT Operation discussion and
diagrams in this section.
E-3
WORK CLAMP
Lout
BS1
WRK
240uH
8A
+12VDC TRANSFER
RL1 NZL (2)
C14
R24
6.8k/5W
SHUNT
EL (3)
SH- SH+
PT
CN3
1
2
3
4
12VDC