GB326657A - Improvements in and relating to electric motors - Google Patents

Abstract

326,657. British Thomson-Houston Co., Ltd., and Dreghorn, H. March 5, 1929. Alternating-current commutator machines. - An alternating-current commutator motor of the type described in Specification 25358/11 is provided with an open type winding, thereby enabling a high speed machine to be obtained with the possibility of speed regulation over a selected range. The windings may consist of coils 3, Figs. 1, each of one or more turns connected at one end to the commutator segments 2 and at the other to a common ring 4, or the coils may be replaced by simple bars passing through the slotted core 1 and connected to the commutator and a ring which is mounted at the end of the shaft remote from the commutator. The conductors may occupy a portion only of the core length in which case the ring is placed in an air space in the core. In small machines, only threo secondary phases need be used, but more are used for large motors, e.g. nine, as shown in Fig. 3. A nine-phase starter may be used, or, alternatively, the machine may be started on three phases a, b, c by means of resistances 6, the other phases being open-circuited until the resistances are cut out. Specification 290,311 also is referred to.