The Main Components of an Alternator

The main components of an alternator start with the case. The case is made of aluminum, since it is non-magnetic. The pulley is attached to the main rotor, which extends through the center of the alternator case. To the rotor is attached a malleable iron core that surrounds the rotor, separated in segments and wrapped with copper wire.

For illustrative purposes, hold both hands out in front of you. Face the fingers in and intertwine them so that there is one left finger followed by a right and so on. This is what the iron core is shaped like. The reason for this is to create a north and south pole when the core is magnetized.

The inside face of the case contains a stator, which is an iron band wrapped with copper wire that surrounds the inside of the case. As the iron core with the field windings is spun between the stator, electrical energy is produced in the stator in the form of alternating current. The more power applied to the field core, the stronger the magnetic force becomes and the more current is produced.

There are internal or external fan blades (depending on the type of alternator) on the rotor to cool the alternator core. The alternator creates heat as the power is produced. The more power applied to the field core, the more heat produced.

There are two slip rings attached to the rear of the field core shaft. Power flows through a set of two carbon brushes in a plastic housing attached to the case. Power travels through the brushes, which contact the slip rings to the field windings, creating the magnetic field.

If the alternator halves are separated and the rotor removed, a rectifier bridge can be seen on the inside rear of the case. This contains three sets of two diodes. These diodes are attached to the stator and allow electrical power travel in only one direction.
This converts the alternating current to direct current useable in the automobile. The rectifier is used to control the amount of power applied to the field windings thus controlling voltage output. It also acts as a regulator where it senses battery voltage indicating the state of charge and regulates the voltage output to maintain the proper charge.

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