The present invention relates to an alternator comprising: an alternator stator (2) comprising a main secondary winding (7) delivering an output voltage; at least one auxiliary winding (3); and an exciter field winding (5) powered by the auxiliary winding(s); a regulator (20) for regulating the output voltage of the alternator; and an alternator rotor (8) comprising an exciter secondary winding (6); a rotary field winding (4) powered by the exciter secondary winding (6); and a control circuit (10) for controlling the power supply to the rotary field winding (4) and configured to maintain the amplitude of the output voltage from the alternator at a predetermined level by controlling the power supply to the rotary field winding (4) in response to a control signal coming from the voltage regulator (20), the auxiliary winding(s) (3) generating a voltage because they are exposed to a varying magnetic field generated by the rotary field winding (4) in rotation.