Theory of operation, Excitation (flashing), Auxiliary and field feedback coils – Lincoln Electric CLASSICII SVM125-A User Manual

Page 47: Interpole and series coils, Engine

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ENGINE, GENERATOR ARMATURE
AND FRAME, ALTERNATOR
STATOR AND ROTOR

EXCITATION (FLASHING)

When the engine is started and running, the residual
magnetism voltage is applied to the alternator rotor via
a brush and slip ring configuration. This excitation
(“flashing”) voltage magnetizes the rotor lamination.
The alternator rotor is connected to the armature shaft,
which is mechanically coupled to the engine. The rotat-
ing magnet (rotor) induces a voltage in the stationary
windings of the alternator stator.

AUXILIARY AND FIELD FEEDBACK COILS

There are two isolated windings incorporated in the sta-
tor lamination assembly. One of these windings is
tapped and provides 115VAC and 230VAC of auxiliary
power to the appropriate receptacles. The other
115VAC isolated winding is rectified to a DC voltage
and is used to supply field feedback voltage to the

rotor. It also supplies voltage, through the generator
field rheostat control, to the field shunt windings in the
main generator frame.

INTERPOLE AND SERIES COILS

The generator armature rotates within the magnetic
field created by the shunt field windings. A DC voltage
is induced in the armature and is transferred, through
the armature commutator and brushes, to the series
and interpole coils. The interpole coils, which are con-
nected in series with the positive output terminal, are
located so as to counteract any magnetic influences
that could cause mechanical distortion in the rotating
armature. The series coils are designed to oppose or
“buck” the DC voltage that is generated in the arma-
ture.

THEORY OF OPERATION

E-3

CLASSIC II