Lincoln Electric PRO-CUT 55 SVM140-A Service Manual page 28

Section E-1
-THEORY OF OPERATION SECTION-
Theory of Operation .............................................................................................................Section E
General Description ....................................................................................................................E-2
Input Line Voltage, Contactor and Main Transformer.................................................................E-2
Precharge and Protection ...........................................................................................................E-3
Main Transformer ........................................................................................................................E-4
Output Board and Torch .............................................................................................................E-5
Control and Display Boards........................................................................................................E-6
Protection Circuits ......................................................................................................................E-7
Overload Protection..............................................................................................................E-7
Thermal Protection ...............................................................................................................E-7
Insulated Gate Bipolar Transistor (IGBT) Operation ...................................................................E-8
Pulse Width Modulation (PWM) ..................................................................................................E-9
INPUT
LINE INPUT
SWITCH RECTIFIER
AIR
PRESSURE
SWITCH
"A"
L
E
A
D
FAN
MOTORS
AUXILIARY
TRANSFORMER
TABLE OF CONTENTS
FIGURE E.1 – PRO-CUT 55 BLOCK LOGIC DIAGRAM
POWER BOARD
CR 1
RELAY
IGBT
CAPACITOR
R
E
IGBT
C
O
N
N
E
C
IGBT
T
TRANSFORMER
S
W
I
CAPACITOR
T
C
H
IGBT
P
R
O
T
CR 1
E IGBT
RELAY
C
GATE
DRIVE
T
SIGNALS
SIGNAL
I
O
N
SIGNAL
CONTROL BOARD
18/36VAC
A
R
I
E
R
THERMOSTATS
A
D L
Y O
W
OUTPUT
CONTROL
DISPLAY BOARD
PRO-CUT 55
MAIN
TRANSFORMER
CURRENT
TRIGGER & SAFETY
ELECTRODE & TRANSFER
CURRENT FEEDBACK
PILOT ENABLE
ELECTRODE SOLENOID ENABLE
AIR SOLENOID ENABLE
T S
H
A
E
F
R
E
M
T
A
Y
L
Section E-1
WORK
NOZZLE
ELECTRODE
TORCH
OUTPUT BOARD CONNECTOR
E
L
E
C
T
R
O
D
E
CHOKE
S
O
PILOT
L
TRANSISTOR
E
N
O
I
D
TRIGGER & SAFETY
AIR
SOLENOID
12VAC
24VAC