What is brushless excitation system?

3 phase synchronous generator or motor require DC current in the rotor. Conventional way of supplying DC requires use of commutators, which requires timely maintenance. To overcome this Brush less Excitation systems is used.

Brushless Escitation system consists of one pilot excitor - DC generator with rotating PM as the field and the armature as the stator. The armature of the pilot excitor is connected to the stator of main excitor which is a 3-phase synchronous generator (please do not get confused, this is not our alternator but the exciter for the alternator). The rotor of the main exciter is connected to a diode bridge to get DC. This is connected to the rotor of our alternator.