Lincoln Electric IDEALARC SP-255 Service Manual page 50

E-4
POWER SUPPLY OPERATION (CONTINUED)
MAIN
LINE
TRANSFORMER
SWITCH
RECONNECT
FAN
MOTORS
WIRE DRIVE MOTOR AND FEEDBACK
The wire drive motor is controlled by the control board.
A motor speed feedback signal is generated at the
motor tach and sent to the control board. The control
board compares this feedback signal with the com-
mands set forth by the keypad (or the gun thumb
switch) and sends the appropriate armature voltage to
the wire drive motor. The drive motor speed is thus con-
trolled which in turn regulates the electrode wire feed
speed through the gun.
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.5 - Wire Drive Motor and Feedback
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
IDEALARC
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
® SP-255
E-4