GB286001A - Improvements in or relating to electrical converters, transformers and the like - Google Patents

Abstract

286,001. Wilmotte, R. M. Nov. 27, 1926. Brush - hnlder.s; improving commutation, auxiliary means for.-In electrical machines employing a segmental commutator, the circuit of each segment is linked with a magnetic core the reluctance of which is so varied as to produce during the period in which the segment is undergoing commutation a balancing E.M.F. in opposition to the commutating E.M.F. As shown in Figs. 1 and 2, the segments of a commutator 10 associated with relatively rotatable brush-gear 17 are connected to the windings 12<a>, 12<b>, 12<c> of a transformer or other machine through coils 29<a>, 29<b> &c. on magnetic cores 24<a>, 24<b> &c. The cores are provided with air gaps 23, and a flux is produced therein by exciting windings 28<a>, 28<b> &c. The required balancing E.M.F. is generated in the coils 29<a>, 29<b> &c. by means of inductors 27 moving synchronously with the brush-gear through the air gaps 23. The inductors are provided with tapering extensions so dimensioned as to vary the effective width of the air gaps to produce a balancing E.M.F. of a suitable characteristic, and are of a length bearing the same ratio to the length of the air gaps as the width of the brush bears to the width of a segment. The inductors are staggered alternately and rotate with the brush-gear when the latter rotates; the brush-gear and inductors may however, be fixedly arranged to co-operate with a rotary commutator and rotary cores. The invention is described more particularly in connection with commutator switch converters, frequency changers, and phase changers, but is also seated to be applicable to dynamo-electric machines to enable the brushes to be shifted for effecting speed control in the case of a motor, and voltage control in the case of a dynamo.