a self - excited brushless alternator having a rotating field winding excited by an alternating current exciter whose rotating armature rotates with the rotating field winding and is permanently connected to the field winding via a field rectifier also mounted to rotate with the field winding . the exciter has an exciter stator primary winding and a rotary exciter secondary winding connected via a rotray field rectifier to the rotary main field winding of the alternator . the primary excitation for the exciter is derived , via magnetic coupling , from a rotary auxiliary magnetic field produced by a feedback winding in series with the main field winding and rotating herewith . a common magnetic circuit couples the rotary feedback winding with an auxiliary stator secondary winding and the exciter primary and secondary windings . the common magnetic circuit has a common stator core having the exciter primary winding and the auxiliary secondary winding thereon and a common rotor core having the exciter secondary winding and the feedback winding thereon . in operation a pole group having either k or nk feedback or exciter pole pairs is formed with poles uniformly disposed around the rotor or 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 , forming the pole group having k pole pairs have one or more first winding portions wounds for generating the poles of that group whereby the net change or magnetic flux linking with each first winding portion and due to the pole group having nk pole pairs is substantially zero .