Lincoln Electric POWER MIG 255 SVM144-B - Manual (Page 31)

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POWER MIG 255
Section E-1 Section E-1
Theory of Operation ...............................................................................................Section E
Input Line Voltage and Main Transformer.....................................................................E-2
Output Rectification and Feedback Control.................................................................E-3
Constant Voltage Output ..............................................................................................E-4
Wire Drive Motor and Feedback...................................................................................E-5
Thermal and Overload Protection.................................................................................E-6
Overcurrent Protection ...........................................................................................E-6
Wire Feed Overload Protection ..............................................................................E-6
SCR Operation..............................................................................................................E-7
TABLE OF CONTENTS
- THEORY OF OPERATION SECTION -
FIGURE E.1 – BLOCK LOGIC DIAGRAM
LINE
SWITCH
RECONNECT
MAIN
TRANSFORMER
SNUBBER
BOARD
RECTIFIER
DIODE
BRIDGE
ARC
VOLTAGE
WIRE
SPEED
GAS
SOLENOID
FAN
MOTOR
CONTROL
BOARD
WIRE
DRIVE
MOTOR
TACH
GUN TRIGGER
FEEDBACK
115 VAC
30 VAC
G
A
T
E
S
I
G
N
A
L
SCR
RECTIFIER
POWER
ENHANCEMENT
CHOKE
OUTPUT
CHOKE
C
A
P
A
C
I
T
O
R
S
F
E
E
D
B
A
C
K
NEGATIVE
TERMINAL
POSITIVE
TERMINAL
SHUNT