Current Range Selector; Fine Current Adjustment; Engine Idler Circuit - Lincoln Electric CLASSICII SVM125-A Service Manual

E-4
FIGURE E.4 – CURRENT RANGE SELECTOR, FINE CURRENT ADJUSTMENT AND ENGINE IDLER CIRCUIT
ON LATER MODELS
PROTECTION AND IDLER CIRCUITS
ARE ON ONE PC BOARD
PROTECTION
OIL
TEMPERATURE
SENSOR
FUEL
SOLENOID
RELAY
CR1
(NOT PRESENT
ON LATER MODELS)
IGNITION
ENGINE
SWITCH
ALTERNATOR
BATTERY
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.
NOTE: Unshaded areas of Block Logic Diagram are the subject of discussion.
THEORY OF OPERATION
RELAY
IDLER
BOARD
IDLER
SOLENOID
OIL
PRESSURE
SENSOR
SERIES
COILS
GENERATOR
ENGINE
MECHANICAL
COUPLING
ARMATURE
STARTER
MOTOR
CLASSIC II
SELECTOR
SWITCH
115 & 230VAC
RECEPTACLES
GENERATOR
FRAME
ALTERNATOR STATOR
ROTOR
ARMATURE
SHAFT
INTERPOLE
RESIDUAL
COILS
MAGNETISM FLASHING
FIELD
SHUNT
WINDINGS
FIELD
RECTIFIER
GENERATOR
FIELD CONTROL

ENGINE IDLER CIRCUIT

The idler solenoid is mechanically connected to the
engine governor linkage.
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.
REED
RELAY
NEGATIVE
CR2
OUTPUT
TERMINAL
CURRENT
TRANSFORMER
SLIP
RINGS
POSITIVE
OUTPUT
TERMINAL
When welding current is
E-4