Switched reluctance motor with fractionally pitched windings and bipolar currents

This paper presents a study of a new switched reluctance motor with fractionally-pitched coils in the stator slots and with bipolar currents. It is shown that both the electric circuit and magnetic circuit are utilized more effectively, compared to the conventional switched reluctance motors with short-pitched coils and with unipolar currents. The mutual coupling among the phases contributes to the torque production. Comparison analysis of the torque density and power density under quasi-square waveform and square waveform current control schemes are presented. Magnetic field analysis, dynamic simulation and prototype testing are presented. In addition to improving the torque density, the bipolar control schemes also make possible the use of the conventional symmetrical bridge circuit and power modules common for AC motors.