New winding configurations for doubly salient reluctance machines

Abstract

This paper develops the concept of employing a fully pitched winding in a doubly-salient reluctance motor. In a conventional switched reluctance machine, there is complete magnetic decoupling between phases, so that torque is produced entirely due to the rate of change of winding self-inductance. This effectively limits each phase to contributing to positive torque production to a maximum of one-half of the cycle of rotation. If the same machine is wound with fully pitched windings, then it can be shown that the new configuration produces torque entirely as a result of changing mutual inductance between phases, while maintaining a unipolar conduction sequence. Compared with the conventional short-pitched winding machine, far better utilization of the electric circuit results, with each phase contributing to positive torque production for at least two-thirds of the cycle of rotation. A subsequent increase in torque per unit volume inevitably results. The application of such an idea to three-phase switched reluctance motors (SRMs) is developed theoretically and through a series of experimental tests upon a 7.5 kW machine, showing static torque curves for the new machine and comparing them to a conventionally wound SRM.