Lincoln Electric IDEALARC SP-250 Service Manual page 43

E-3
POWER SUPPLY OPERATION (CONTINUED)
MAIN
LINE
TRANSFORMER
SWITCH
RECONNECT
FAN
MOTORS
CONSTANT VOLTAGE OUTPUT
The controlled DC output from the SCR rectifier
assembly is filtered by the capacitor bank and the out-
put choke, which is in series with the gun and welding
load, resulting in a constant voltage output at the out-
put terminals of the machine.
THEORY OF OPERATION
PIEZO GAS
ALARM SOLENOID
LCD
DISPLAY
KEYPAD
CONTROL BOARD
G
A
T
E
S
I
G
N
A
L
SCR
RECTIFIER
Figure E.4 - Constant Voltage Output
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
IDEALARC SP-250
WIRE
DRIVE
MOTOR
TACH
GUN TRIGGER AND THUMB SWITCH
FEEDBACK
POSITIVE
TERMINAL
CHOKE
C
A F
P E
A E
C D
I B
T A
O C
R K
NEGATIVE
S
TERMINAL
SHUNT
E-3