Self-compensating brushless alternator

A self-excited alternator of the brushless type, having a rotating field which is excited by an alternating current exciter whose rotating armature is mounted to rotate with the rotating field winding of the alternator and is permanently connected to the field winding of the alternator via field rectifier means also mounted to rotate with the field winding wherein the exciter has an exciter stator primary winding and a rotary exciter secondary winding connected via rotary field rectifier means to the rotary main field winding of the alternator, primary excitation direct current for the exciter being derived, via magnetic coupling, from a rotary auxiliary magnetic field produced by a feedback primary winding connected in series with the main field winding and mounted to rotate therewith, and wherein a common magnetic circuit is used for coupling the feedback primary winding with a feedback secondary winding and for coupling the exciter primary and secondary windings, the common magnetic circuit comprising a common stator core on which the exciter primary winding and the auxiliary secondary winding are provided and a common rotor core on which the exciter secondary winding and the feedback winding are provided, the rotor core being so shaped and the feedback winding being so provided thereon that in operation a pole group having either K or NK feedback pole pairs is formed with poles uniformly disposed around the rotor core and the stator core being so shaped and the exciter winding being so provided thereon that in operation a pole group having either NK or K exciter pole pairs are formed with poles uniformly disposed around the stator core, the ratio of feedback pole pairs to exciter pole pairs being either K to NK or NK to K, where K is any number and N is an even number, either the feedback winding or the exciter primary winding, as the case may be, for forming the pole group having K pole pairs comprising one or more first winding portions wound for generating the poles of that group whereby, with rotation of the rotor core relative to the stator core, the net change of magnetic flux linking with each first winding portion and due to the pole group having NK pole pairs is substantially zero.