How An Automotive Alternator Works



Automotive Alternators 101.
(This is where you learn what you are talking about...)


There are about 5 basic components to an alternator that are common to all automotive brands...


1. The Regulator. The Voltage Regulator controls the current going to the Rotor.
An Increase in current to the Rotor means a stronger magnetic field & more alternator output, Less current to the rotor means a weaker magnetic field & Less alternator output.
The voltage regulator samples the out going DC current from the alternator, and decides if more or less current is needed at the Rotor.
For more on regulators, click here.

2. The Slip Rings. The current supplied from the Voltage regulator has to reach the Rotor.
This is done via 'Brushes' and 'Slip Rings'.
The regulator output is carried by the 'Brushes' to the 'Slip Rings'.
The Slip Rings are directly connected to the electro-magnet in the rotor.



3. The Rotor. The Rotor is the spinning mass inside of the alternator the belt turns .
The Rotor is a spinning electro-magnet.
The Rotor's electrical magnet is supplied by 'Slip Rings'.
The Rotor has an iron plate on both ends of the electro-magnet, cut like the pedals of a dazy.
One is the North Magnetic Pole, the other is the South Magnetic Pole.
The 'Pedals' of the Poles are bent over the outside of the electro-magnet, to make 'Pole Faces' .
These 'Pole Faces' are bent to face the Stator Windings located around the 'Equator' of the alternator case.


This Is An Actual Alternator Rotor Showing Sliprings, Electro-Magnet & Magnetic Pole Faces.

4. The Stator.
The Stator is an Iron ring with sever coils of wire wound through it.
The Rotor spins inside of the Stator.
When the magnetic field created by the Rotor bisects the coils of wire, an electrical current is induced.
(for more on Induction, click here. ..)
The average alternator has three seprate sets of windings, spaced 120 degrees apart.
The Stator will produce 3-Phase AC current.

5. The Rectifier.
The 3-Phase AC current will be passed off to two sets of Diodes.
Diodes are one way electrical valves. Current will pass one way, but not the other.
The First set of Diodes is for the positive current to pass through, the second set of Diodes are for the returning current (negitive).
These diode sets 'Rectify' the Alternating Current (AC), into a useable form of Direct Current (DC).
For more on the basic electrical principals, click here.