Speed-changing induction motors. Further developments in pole-amplitude modulation

An earlier paper has described the basic steps which led to a practical form of 8/10-pole induction motor, of good performance, having only one stator winding. The principle on which this speed-changing motor was based has been given the name of `pole-amplitude modulation¿. Since the publication of the original account of it, the principle has been further developed, and a number of improvements in the method have been devised and tested in practice on several new forms of 8/10-pole motor. This paper discusses the theory and tests on these new machines, which are of interest both in themselves and for the further light which they throw on the principles of pole-amplitude modulation. The tests were completely successful, and this type of machine is now in the repertory of several manufacturers as an established industrial product.