THEORY OF OPERATION
E-4
E-4
CV-655
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PROTECTIVE DEVICES AND
SHUTDOWN CIRCUITS
THERMAL PROTECTION
Two thermostats protect the CV-655 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 temperatures should
occur, a thermostat will open. This condition will be
indicated by the illumination of the yellow
Thermostatic Protection Light located on the case
front. The fan should continue to run, but the welding
output will be disabled until the machine cools and the
Thermostatic Protection Light is out.
OVER CURRENT PROTECTION
The CV-655 also has over-current protection. When
the load exceeds a threshold current (about 900
amps), overcurrent shutdown will occur after a period
of time that shortens as the current increases beyond
this threshold. If the current reaches about 1000 amps
the output will be “clamped” at about 1000 amps and
shut down will occur in about 5 seconds. When this
overload shut down occurs the short circuit output of
the machine drops to only about 20 amps, but the
input contactor and input pilot light will remain on until
reset. This is done by turning the power switch off,
then back on with the overload removed.
FAN MOTOR FUSE
(EUROPEAN MODEL)
A 10 amp slow blow fuse protects the fan motor cir-
cuit. This fuse is located inside the CV-655 mounted
on the fan motor bracket.
