Input Power Circuit; Dc Welding Output; Ac Welding Output - Lincoln Electric SQUARE WAVE SVM141-A Service Manual

Section E-1
- THEORY OF OPERATION SECTION -
Theory of Operation .............................................................................................................Section E
General Description ....................................................................................................................E-2
Input Power Circuit......................................................................................................................E-2
Output Rectification, Control Board and Feedback ....................................................................E-3
High Voltage/High Frequency Circuit ..........................................................................................E-4
DC Welding Output .....................................................................................................................E-5
AC Welding Output .....................................................................................................................E-6
SCR Operation............................................................................................................................E-7
Protective Circuits .......................................................................................................................E-8
Thermal Protection ...............................................................................................................E-8
Overload Protection ..............................................................................................................E-8
FIGURE E.1 - SQUARE WAVE TIG 275 BLOCK LOGIC DIAGRAM
INPUT
RECONNECT POWER
PANEL SWITCH
"A"
115VAC
RECEPTACLE
TABLE OF CONTENTS
MAIN
TRANSFORMER
H1
X1
H2
X2
H3
H4
23VAC
18VAC
18VAC
115VAC
FAN
REMOTE
RECEPTACLE
DOWNSLOPE
CONTROL
SQUARE WAVE TIG 275
BY-PASS
BOARD
POLARITY
SWITCH
C
H
O
AC DC+
K
SCR
E
BRIDGE
SHUNT
TRANSFORMER
DC-
AC
F
E
E
D
B
A
C
K
115VAC
CONTROL
BOARD
GAS POSTFLOW OUTPUT
BALANCE
VALVE CONTROL CONTROL
CONTROL
Section E-1
WORK
ELECTRODE
HI-FREQUENCY
TRANSFORMER
HIGH VOLTAGE
CIRCUIT
MODE
SWITCH
THERMAL
LIGHT
THERMOSTATS