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TM 9-8000
Figure 13-4. Field Winding Configurations.
field frame that forms the magnetic circuit between the
regulation circuitry used, the field windings may be
poles. Although machines may be designed to have
connected in one of two ways.
any even number of poles, two-and four-pole frames
a. A-Type Field Circuit. The A-type field circuit shunts
are the most common.
one end of the field winding to the negative generator
c. Field Frames. In the two-pole type frame, the
brush and controls output through the regulation circuitry
magnetic circuit flows directly across the armature,
to the positive (battery) connection.
while in the four-pole type each magnetic circuit flows
b. B-Type Field Circuit. The B-type field circuit shunts
through only a part of the armature core. Therefore,
the armature must be constructed in accordance with
one end of the field winding to the positive generator
the number of field poles because current is generated
brush and controls output through the regulation circuitry
when the coil, winding on the armature, moves across
to the negative (ground) connection.
each magnetic circuit.
d Brushes and Commutator.  The current is
13-8. Shunt-Wound Generator (Fig. 13-5).
collected from the armature coils by the brushes
a. General.  Most motor vehicle generators are shunt
(usually made of carbon) that make rubbing contact
wound, with an outside means of regulating the voltage
with a commutator.  The commutator consists of a
output. Approximately 8 to 12 percent of the total current
series of insulated copper segments mounted on one
generated by the armature is shunted (sent) through the
end of the armature, each segment connecting to one
field coils for producing the magnetic field.
or more armature coils.  The armature coils are
connected to the external  circuit (battery, lights, or
b. Components. The generator essentially consists of
ignition) through the commutator and brushes. Current
an armature, a field frame, field coils, and a commutator
induced in the armature coils thus is able to flow to the
with brushes to establish electrical contact with the
external circuit.
rotating element. The magnetic field of the generator
Principle of Operation.  In figure 13-6,
usually is  produced  by  electromagnets  or  poles
assume that the magnetic field flows from the north
magnetized by current flowing through the field coils.
pole piece (N) to the south pole piece (S), as indicated
Soft iron pole pieces (or pole shoes) are contained in the
by the arrows. When the armature is


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