Magnetic design of two-phase switched reluctance motor with bidirectional startup capability

The symmetric structure conventionally used in two-phase switched reluctance machines (SRMs) leads to dead torque zone and issues with startup. When a phase is at the fully aligned position with respect to the rotor, the complimentary phase is completely unaligned. Within this region, excitation of either phase fails to generate sufficient startup torque. Significant research has been focused on the design of machines with large, unidirectional startup torque specific to the direction of rotation required by the given application. In this work, a conventional two-phase SRM is analyzed to reveal the underlying geometric constraints leading to startup difficulties. To overcome this, a phase shift design strategy is proposed to ensure both large starting torque and bidirectional startup capability. The design is investigated and validated through both simulation and experiments, and the results show the validity of this new configuration.