GB1361273A - Excitation of brushless alternators - Google Patents

Abstract

1361273 A.C. generators with D.C. excitation BRUSH ELECTRICAL ENG CO Ltd 6 Oct 1972 [9 July 1971] 32249/71 Heading H2A In a brushless alternator incorporating a brushless exciter whose main field winding 19 is provided with electrical power by a pilot exciter, the latter comprises a plurality of magnetizable interpoles 20 which are defined as auxiliary poles, each having at least two teeth 23 located between exciter main poles 18 and having associated A.C. coils 22 which are interconnected to provide an output winding connected through a rectifier 28 to the exciter field winding 19, the teeth moreover co-operating with teeth 17 in the adjacent surface of the exciter armature 16 to produce magnetic flux pulsations and thereby induce in the output winding a current which after rectification by the rectifier 28 serves as the exciter excitation current. As shown, the alternator comprises stationary polyphase armature windings 26 and a rotor field winding 25 supplied via a shaft mounted rectifier comprising diodes 24 by the exciter A.C. armature winding 14 which is accommodated in open slots defined by teeth 17. Each interpole may have a D.C. excitation winding 21 fed, through a rheostat 30, also from its A.C. coils 22, remanent magnetism in the exciter yoke 15 or the interpoles 20 being sufficient to ensure excitation build-up during starting; alternatively, the body of each interpole may incorporate a permanent magnet. The alternator excitation may be controlled by a manually-operable rheostat in a stabilized automatic voltage regulator 27 fed from the armature winding 26.