Two-speed single-winding salient-pole synchronous machines

Previous work on 2-speed single-winding squirrel-cage induction motors, using the principle of pole-amplitude modulation, has now been extended to synchronous machines, and really simple and satisfactory 2-speed salient-pole synchronous motors have been designed, constructed and tested. This paper records the basic principles involved and illustrates these by reference to an industrial 10/8-pole motor of this type, for which test results are given. Such motors can equally well be used as generators, either to give a choice of output frequency for a given speed of prime mover or to maintain the output frequency constant in spite of a change of driving speed.