Alternator: Description and Operation

An alternator is composed of the same functional parts as a conventional D.C. generator, but operates differently. The rotor is the turning portion of the unit and corresponds to the field of a generator. The stator or generating part, is the stationary member, comparable to the armature in a D.C. generator. The regulator, similar to those used in a D.C. system, regulates the output of the alternator-rectifier system.
The power source of the system is the alternator. Current is transmitted from the field terminal of the regulator through a slip ring to the field coil and back to ground through another slip ring. The strength of the field is varied to regulate the alternating current output. This alternating current flows from the alternator to the rectifier where it is converted into direct current.
These alternators employ a three-phase stator winding in which the phase windings are electrically 120 degrees apart. The rotor consists of a field coil encased between interleaved sections producing a magnetic field with alternate north and south poles. By rotating the rotor inside the stator alternating current is induced in the stator windings. This alternating current is rectified (changed to D.C.) by a silicon diode rectifier, and is made available, as D.C., at the output terminal of the alternator.