Figure 2-22.Rotor assembly.
The primary components of an alternator are as
ROTOR ASSEMBLY (rotor shaft, slip rings,
claw poles, and field windings)
STATOR ASSEMBLY (three stator windings
or coils, output wires, and stator core)
RECTIFIER ASSEMBLY (heat sink, diodes,
diode plate, and electrical terminals)
ROTOR ASSEMBLY (fig. 2-22).The rotor
consists of field windings (wire wound into a coil
placed over an iron core) mounted on the rotor shaft.
Two claw-shaped pole pieces surround the field
windings to increase the magnetic field.
The fingers on one of the claw-shaped pole pieces
produce south (S) poles and the other produces north
(N) poles. As the rotor rotates inside the alternator,
alternating N-S-N-S polarity and ac current is
produced (fig. 2-23). An external source of electricity
is required to excite the magnetic field of the
Slip rings are mounted on the rotor shaft to provide
current to the rotor windings. Each end of the field coil
connects to the slip rings.
STATOR ASSEMBLY (fig. 2-24).The stator
produces the electrical output of the alternator. The
stator, which is part of the alternator frame when
assembled, consists of three groups of windings or
coils which produce three separate ac currents. This is
known as three-phase output. One end of the windings
is connected to the stator assembly and the other is
connected to a rectifier assembly. The windings are
Figure 2-23.Simple alternator illustrating reversing
magnetic field and resulting current flow.
Figure 2-24.Stator assembly.
wrapped around a soft laminated iron core that
concentrates and strengthen the magnetic field
around the stator windings. There are two types of
statorsY -type stator and delta-type stator.