Switched reluctance bearingless motors

This chapter provides an introduction to the bearingless switched reluctance motor. The switched reluctance motor offers the possibility of operation as a bearingless motor. Torque is generated by magnetic attraction between rotor and stator poles. In this process, a significant amount of attractive radial force is generated because the switched reluctance motor has salient poles. A short airgap length between these poles effectively produces a reluctance torque. It is possible to take an advantage of the inherent high radial force that is produced for rotor shaft magnetic suspension. Therefore, bearingless switched reluctance motors with differential stator winding configurations have been developed. These motors have motor windings and suspension windings wound in the same stator to produce a suspension force that can realize rotor shaft suspension. Hence, these motors are expected to be suitable for maintenance-free drives used in special circumstances, such as high temperature, wide temperature variation, and high acceleration operation. The chapter also presents a discussion on a drive system, which controls the average torque and instantaneous suspension force to produce stable operation.