GB293936A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

293,936. British Thomson-Houston Co., Ltd., and Maggs, A. H. May 11, 1927. Alternating-current commutator machines.-A compensated induction motor or other machine has on the stator primary windings and compensating windings which are connected by means of adjustable brushes on the stator, equivalent to a fixed commutator, to a secondary winding on the rotor through a segmental collector ring equivalent to rotating brushes. The secondary windings may also have slip-rings for the insertion of .an external resistance between the phases. Fig. 1 shows the windings for a 2-pole machine in which the stator carries the primary and compensating windings 10, 11, usually separate, as shown, although they may be combined, with tappings 13 to an adjustable fixed " commutator." The taps 13 are preferably high resistance elements, and the " commutator," as shown in Fig. 3, consists of brush rows 14 on a rocker. These bear on a collector 16 of ordinary commutator construction mounted on the rotor and comprising segments 17, Fig. 1, connected to the secondary phase terminals. The segments are separated by segments 18 of insulating material or by idle metal segments. The other ends of the rotor phases 12 are connected to slip-rings 20 for the insertion of starting or speed-regulating resistances. Movement of the brush rocker controls the power-factor of the machine. The connections between the compensating and secondary windings are shown in Fig. 2 for an 8-pole machine in which the phase terminal segments 17 are separated by idle segments 18. The segments 17 are connected to bus-rings 21, 22, 23 and each one is flanked by segments 17<1> connected in sequence to the bus-rings through resistances 19 to assist commutation. The number of segments 17 equals the product of the numbers of secondary pole-pairs and phases. The other ends of the secondary windings 12 may be short-circuited or connected to slip-rings, as shown. The total number of brushes may be the same as or a multiple of the number of segments per pole-pair of the fixed commutator equivalent.