Lincoln Electric IDEALARC DC-655 - Manual (Page 37)

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Section E-1 Section E-1
IDEALARC DC-655
Theory of Operation ............................................................................................................. Section E
General Description ....................................................................................................................E-2
Input Line Voltage, Contactor, Reconnect,
Fault Protection, Main and Control Transformers.......................................................................E-2
Control Board, Firing Board, Snubber/Fan
Board and Rectification ..............................................................................................................E-3
Protective Devices and Shutdown Circuits ................................................................................E-4
Thermal Protection ...............................................................................................................E-4
Over Current Protection .......................................................................................................E-4
Peak Current Protection .......................................................................................................E-4
Remote Control Fault Protection..........................................................................................E-4
Shorted Output Rectifier Fault Protection............................................................................E-4
SCR Operation ............................................................................................................................E-5
TABLE OF CONTENTS
-THEORY OF OPERATION SECTION-
CONTROL
TRANSFORMER
R
E
C
O
N
N
E
C
T
CONTACTOR
FAULT PROTECTION
115VAC
MAIN
TRANSFORMER
CONTROL
BOARD
SHUNT
OUTPUT
CONTROL
MODE
SWITCH
POSITIVE
TERMINAL
NEGATIVE
TERMINAL
LATCHING
RESISTOR
F
E
E
D
B
A
C
K
F
E
E
D
B
A
C
K
SCR BRIDGE
42VAC
115VAC
42VAC
T
E
R
M
I
N
A
L
S
T
R
I
P
TO OPTIONAL
METER BOARD
HIGH
LOW
ARC FORCE
CONTROL
FIRING
BOARD
SNUBBER
FAN
BOARD
CR2
CONTROL
BOARD
TRANSFORMER
CR1
CHOKE
14-pin
Amphenol
115VAC
Receptacle
Fan
Motor Fan
Thermal
Sensor
42VAC 10VAC10VAC
32VAC
32VAC
32VAC
SIGNAL
G
A
T
E
S
I
G
N
A
L
GATE SIGNAL
OUTPUT
CONTROL
FIGURE E.1 – DC-655 BLOCK LOGIC DIAGRAM