Power Supply Operation - Lincoln Electric IDEALARC SP-250 Service Manual

E-1
MAIN
LINE
TRANSFORMER
SWITCH
RECONNECT
FAN
MOTORS
INPUT LINE VOLTAGE AND MAIN TRANS-
FORMER
The desired single phase input power is connected to
the SP-250 through a line switch located on the front
panel.
A reconnect panel allows the user to configure the
machine for the desired input voltage. This AC input
voltage is applied to the primary of the main trans-
former and to the thermostatically controlled fan
motors. The transformer changes the high voltage, low
current input power to a low voltage, high current out-
put. In addition, the main transformer also has an iso-
lated center tapped 30VAC auxiliary winding that sup-
plies power to the Control Board for SCR gate drive
and gas solenoid operation. The weld power windings
connect to the Control Board as well as to the main
SCR Rectifier.
THEORY OF OPERATION

POWER SUPPLY OPERATION

PIEZO GAS
ALARM SOLENOID
LCD
DISPLAY
KEYPAD
CONTROL BOARD
G
A
T
E
S
I
G
N
A
L
SCR
RECTIFIER
Figure E.2 - Input Line Voltage and Main Transformer
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-1