Theory of operation, Trigger and control circuits, Ln-15 – Lincoln Electric LN-15 WIRE FEEDER SVM166-A User Manual

Page 35

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LN-15

THEORY OF OPERATION

TRIGGER AND CONTROL CIRCUITS

When the gun trigger is closed (activated) the Feed
Head Board is “signaled” to apply armature voltage
to the drive motor, activate the gas solenoid and
close the LN-15 internal contactor. When the con-
tactor is closed the welding current path from the
electrode cable to the conductor block is completed.
This sequence will supply electrode wire, arc voltage
and current to the welding gun.

The Cold Inch/Gas Purge Switch allows the user to
feed wire without closing the contactor. This feature
gives the operator an electrically “cold” electrode
even though the power source’s output terminals are
electrically “hot”. This switch also allows the user to
activate the gas solenoid without feeding wire or
closing the contactor.

When activated the Trigger Interlock Switch keeps
the gun trigger circuit closed even when the operator
releases the trigger. This is useful when making long
welds.

E-3