GB115509A - Improvements in Self-regulating Dynamo-electric Machines. - Google Patents

Abstract

115,509. Holt, W., and Brooks, B. May 22, 1917. Exciting.-To obtain a constant voltage or current from a self-regulating variable-speed dynamo, the cross-magnetization due to the armature load current is wholly or partially neutralized by means of a compensating winding on the field magnet, a closed winding or circuit is provided on the armature to produce a second cross-magnetization, and supplementary brushes are utilized for demagnetizing the main field-magnet poles. In one modification, Fig. 1, a separate short circuited armature winding b of high resistance and as non-inductive as possible produces by its rotation in the field of the main poles d a magnetic field received by supplementary poles c. The coils of the main armature winding which are under the poles e are spanned by two separated main and supplementary brushes f, f<1> which are electrically connected so as to produce a demagnetizing effect on the main poles d, as described in Specification 26880/10. Compensating-coils g are mounted on the poles e to neutralize or under or over compensate the field due to the load current. The salient poles c may be omitted by bringing the sides of the fieldmagnet yoke close to the armature; a few! series turns may be provided on the main poles d. Instead of directly short-circuiting the brushes f, f<1>, they may be connected through coils on the poles d; or the exciting-coils c may be connected across the main and supplementary brushes situated on opposite sides of a main pole d. The brushes f<1> may be placed under the poles d. The winding b may be joined through slip-rings to a variable resistance. In place of the alternating- current winding b, a second commutator winding b', Fig. 5, may be provided on the armature, having its brushes b<2> either short-circuited or connected through a resistance b<3>. In further modifications, the armature is provided with a single commutator winding, either having tappings connected through resistances as described in Specification 15686/13, or having the main brushes cross-connected through a resistance.