Originally Posted by jay_bob

Check your charging indicator on the dash, it is part of the regulator circuit. Without the bulb in circuit the regulator has no power. If the regulator and field do not get power, the alternator will not produce electricity.

Seems kind of weird, you need to give the alternator some electricity to have it produce but that is exactly how it works. The small energy input from the field combined with the rotational energy from the pulley (less the losses) creates the output energy.

The big generators I work with are exactly the same (2.5 MW) except the field exciter gets its power from a small permanent magnet generator on the end of the main shaft. To sync the generator to the bus we alter the voltage by biasing the field excitiation. Zero excitation on the field means no output voltage.

(and we have to match frequency and phase angle too, much easier with the modern computer controlled direct injection engines)

These get driven by 16 cylinder diesel engines larger than my entire car. And of course there are no diodes, we are making lots of three phase to keep those servers running and cooled when the power company can't.