Circuit Protection; Avoiding Ground Lead Protector (Glp) Activation - Lincoln Electric LN-8 SVM132-A Service Manual

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CIRCUIT PROTECTION

FIELD CIRCUIT FUSE. This 1/2 amp slow blow fuse,
located on the Relay PC board, protects the field cir-
cuit. It will blow if the field shorts or if one of the field
circuit components on the Relay PC board fails.
MOTOR THERMAL PROTECTION. The temperature
sensing thermal protector mounted in the motor opens
the relay circuit when the motor overheats because of
excessive loading or frequent triggering. This protects
the motor without nuisance tripping. The thermal pro-
tector automatically resets itself after the motor cools
sufficiently (may take 10-15 minutes). Reset time can
be shortened by cooling the motor with an air hose or
fan.
CIRCUIT BREAKER. The 5 amp circuit breaker locat-
ed above the drive rolls normally trips only when an
overload occurs because of excessive loading in the
wire feed cable, or a defective motor or control com-
ponent. After allowing a minute for cooling, push the
reset button and weld. If it trips again, be sure the wire
feed cable is clean and the proper size for the wire
diameter being fed. If it still trips, look for a defective
electrical component.
OPERATION
AVOIDING GROUND LEAD
PROTECTOR (GLP) ACTIVATION
The frame of the LN-8 wire feed unit and the drive
motor are grounded to the frame of the power source
by a lead in the control cable. An overload protector
prevents welding current from damaging this lead if
the electrode circuit touches the wire feeder frame
while the gun trigger is pressed.
When the protector is tripped, the welding contactor in
the power source will not close when the gun trigger is
pressed.
DO NOT allow the electrode to contact the case of the
wire feeder or the uninsulated part of the wire reel
stand when the gun trigger is activated.
Be sure that all work lead connections to the work
make tight metal-to-metal contact.
DO NOT allow excess input cable or work cable to be
placed closer than three feet from the wire feeder.
DO NOT coil excess input cable assembly or use a
coiled assembly as shipped from the factory. Instead,
loop the excess cable length back and forth in three to
six foot straight lengths. Coiling the input cable results
in a transformer action between the electrode
conductor cable and the ground lead in the
multiconductor control cable. This transformer action
can cause a current to flow in the ground lead which
will falsely activate the GLP circuit.
To reset the GLP circuit, press the white button above
the drive motor and to the right of the circuit breaker.
LN-8
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