Some developments in multi-speed cascade induction motors

The paper is divided into four Sections and an Appendix. (1) Section I reviews previous work and shows that earlier conceptions were capable of very wide generalization. By this means many new combinations are brought to light, both in principle and in construction distinct from any hitherto described. (2) Section II is a discussion of the theory of the cascade motor from a new point of view, which avoids the difficulties that have hitherto prevented the subject becoming known in its full generality. (3) Section III and the Appendix describe some new rotor windings which remove some existing limitations of the cascade type. Hitherto single-speed machines running faster than 500 r.p.m. (on 50 periods) could not be built, but the present paper describes a machine capable of running at 750 r.p.m. With three speeds in the ratios 1 500/750/500 there are often either too few speeds or too great an interval between them. Apparatus is described giving as many more speeds as desired, with smaller intervals between them, particularly a machine giving speeds in the ratios 750/500/375/300 and having the characteristics of known cascade machines at every speed. (4) Section IV describes stator windings corresponding to the above rotor windings.