Wire Drive Motor And Feedback - Lincoln Electric POWER MIG 255 SVM144-B Service Manual

E-5
FIGURE E.5 — WIRE DRIVE MOTOR AND FEEDBACK.
115 VAC
LINE
SWITCH
RECONNECT
TRANSFORMER
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
THEORY OF OPERATION
GAS
MOTOR
SOLENOID
WIRE
SPEED
CONTROL
ARC
BOARD
VOLTAGE
RECTIFIER
DIODE
G
BRIDGE
A
T
30 VAC
E
SNUBBER
S
BOARD
I
G
N
A
L
POWER
ENHANCEMENT
CHOKE
MAIN
SCR
RECTIFIER
NOTE: Unshaded areas of Block Logic
Diagram are the subject of discussion
POWER MIG 255
FAN
WIRE
DRIVE
MOTOR
TACH
GUN TRIGGER
FEEDBACK
C OUTPUT
POSITIVE
F
A CHOKE
TERMINAL
E
P
E
A
D
C
B
I
A
T
C
O
NEGATIVE
K
R
TERMINAL
S
SHUNT
board compares this feedback signal with the com-
mands set forth by the Wire Speed Control poten-
tiometer and sends the appropriate armature voltage to
the wire drive motor. The drive motor speed is thus
controlled which in turn regulates the electrode wire
feed speed through the gun.
E-5