In general, the amount of electricity generated can be changed by the following methods

	Increase or decrease the magnetic (rotor) force.
	Speed up or slow down the rotational speed of the magnet (rotor).
The rotational speed of the rotor cannot be controlled, because it is rotated according to the engine speed. Therefore, the only condition that can be freely changed in the vehicle's alternator is the magnetic (rotor) force, and changing the amount of current flowing into the rotor coil (field current) changes this magnetic force. The IC regulator regulates the amount of electricity produced by the alternator by controlling the field current so that the generated voltage remains constant regardless of the change in the rotating speed of the rotor and the amount of electricity required (i.e. the increase / decrease in the electrical load).