Protection Devices And Circuits - Lincoln Electric Idealarc DC600 9773MSP Service Manual

E-4
FIGURE E.4 Protection Devices and Circuits (Contactor Hold-In)
CONTROL
TRANSFORMER PROTECTION
DEVICES &
115 VAC
(
CONTACTOR
R
E
C
O
N
N
E
C
T
CONTACTOR
TERMINAL
REMOTE
TO
CONTROL
CONTROL
BOARD
PROTECTION DEVICES AND
CIRCUITS (CONTACTOR HOLD-IN)
Two thermostats protect the DC-600 from excessive
operating temperatures. Excessive operating temper-
atures may be caused by a lack of cooling air or oper-
ating the machine beyond the duty cycle and output
rating. If excessive operating temperature should
occur, the thermostat(s) will deactivate the input con-
tactor, turning the machine off. The input contactor will
remain open until the machine cools. The machine
can then be restarted by operating the start push but-
ton.
Upon restart if the fan does not turn or the air intake
louvers are obstructed, then the input power must be
removed and the fan problem or air obstruction be
corrected.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
IDEALARC DC-600
THEORY OF OPERATION
115 VAC
FAULT PROTECTION
CIRCUTS
)
HOLD-IN
MAIN
TRANSFORMER
STRIP 1
1
5
V
A
C
FAN
OUTPUT
CONTROL
CONTROL
FIRING BOARD
BOARD
F
E
E
PILOT
D
RELAY
B
A
C
K
SHUNT
SCR BRIDGE
CHOKE
The DC-600 is also protected against high current
overloads. This electronic protection circuit senses an
overload on the power source and opens the input con-
tactor should the overload remain for a predetermined
time. If the overload is great the machine will shut
down immediately. The input contactor will remain
open until the start push button is operated.
The Remote Control circuit is also protected from
"grounds" or voltage intrusions. If the #75, #76 or #77
leads come in contact with either of the machine's out-
put cables, the DC-600 will only operate at a minimum
output or the input contactor will open.
MODE
SWITCH
POSITIVE
TERMINAL
F
E
E
PILOT
D
RELAY
B
A
C
K
LATCHING
RESISTOR
NEGATIVE
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