Generator Internal Charging Circuit
As with most vehicle AC generators, there is only minimal residual magnetism in the field (rotor) windings. To compensate for this and to achieve high current output at low engine speed, the field is excited by battery voltage supplied to the generator at the IG terminal. To control the level of field excitation and ultimately generator output, the voltage supplied to the field (rotor) is controlled by the voltage regulator. The voltage regulator senses battery terminal voltage at the B terminal (positive main output terminal), which within limits is proportional to the state of charge of the battery. The regulator then adjusts the supplied voltage between the IG terminal and the regulator F terminal (a continuously variable process) to maintain the positive main output (B terminal) at a constant level. If the field were not controlled, the positive main output would rise to a level which could damage bulbs and ECMs. The regulator compares the output voltage to an internal voltage reference circuit to achieve the controlled output of the generator. See Fig 1 .