Question

Define voltage regulation of an alternator. is it possible to have the full-load terminal voltage greater than the no-load terminal voltage? explain.

Answer 1

The regulation ceases to operate when load is disconnected, for most types of regulator, and a good thing it is, since the circuit is no longer a closed loop and regulation is normally not designed to draw negative current (see attached image of buck converter, for example). Having a little leaking current is frowned upon nowadays due to energy saving requirements.

If there is no signal error there will be no regulation, and the theoretical zero error in a PID regulator occurs after infinite time, at least not before load changes.

Stability is usually required, so there is a choice between small error or high bandwidth.

Filters (low pass) are added to eliminate noise (ripple and hum). Also in a switching converter. Even a tiny capacitor holds a charge and the accompanying resistance adds to the impedance.

All of these combine to decrease the output voltage under load.