Car Generator (VW Passat B3)

The VW PASSAT is equipped with an alternator. Depending on the model and version, alternators with a current of 65 A to 90 A can be installed.

The generator is driven by a V-belt from the crankshaft. The rotor with the excitation winding rotates relative to the stationary stator at a frequency approximately twice the crankshaft rotation frequency.

The excitation current flows through the excitation winding via the brushes and slip rings. This creates a magnetic field whose position relative to the stator constantly changes in accordance with the rotor speed. This causes alternating current to arise in the stator winding.

But since the battery can only be charged with direct current, the alternating current is converted into direct current using a rectifier on semiconductor diodes. The relay regulator changes the charging current by switching the excitation current on and off according to the battery charge level.

At the same time, the voltage regulator maintains the operating voltage constant and equal to approximately 14 volts, regardless of the generator rotor speed.

Caution: Unlike a DC generator, an AC generator should never be operated without a battery, since the engine cannot be started without a battery.