Theory of operation, Current range selector, Fine current adjustment – Lincoln Electric CLASSICII SVM125-A User Manual

Page 48: Engine idler circuit, Engine

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ENGINE, GENERATOR ARMATURE
AND FRAME, ALTERNATOR STA-
TOR AND ROTOR (CONTINUED)

CURRENT RANGE SELECTOR

The selector switch acts as a coarse current adjust-
ment by allowing for varying amounts of series wind-
ings to be included in the welding current path. The
series coils and selector switch are connected in series
with the negative output terminal.

FINE CURRENT ADJUSTMENT

The field rheostat control functions as a fine output cur-
rent adjustment by controlling the current through the
shunt windings. This controls the amount of magnet-
ism created in the shunt field windings. Open circuit
weld voltage can also be controlled by the field rheo-
stat control.

ENGINE IDLER CIRCUIT

The idler solenoid is mechanically connected to the
engine governor linkage. When welding current is
being drawn, the reed switch CR2 is closed. This sig-
nals the idler PC board to release (deactivate) the idler
solenoid, which then lets the machine go to a high
speed condition. Also, when auxiliary power is being
used, the current is passed through the current trans-
former. This signals the idler PC board to release the
idler solenoid.

When welding ceases or the auxiliary load is removed,
a preset time delay of about 15 seconds starts. After
approximately 15 seconds the idler PC board activates
the idler solenoid, and the machine will return to a low
speed condition.

THEORY OF OPERATION

E-4

CLASSIC II