In the alternator a magnetic field rotates and the conductors are stationary. Mechanical energy is converted to electrical energy by electromagnetic induction.
The value of the induced EMF depends on the strength of the magnetic field, the speed at which the magnet rotates and the number of turns of wire on the stationary coil.
Automotive alternators use a three-phase bridge rectifier that has three positive diodes and three negative diodes to rectify the AC current in the three-phase stator windings and produce a DC output.
When the ignition is first switched, current flows through the charge indication lamp, the rotor windings and voltage regulator to ground. Current flow through the rotor winding is controlled by the voltage regulator when the engine is running.
Vehicles have traditionally used 12-volt batteries and a 14-volt charging system, but to meet the increased demand from such high usage systems as electric drives, higher voltage batteries and packs with an appropriately high voltage charging system are necessary.
