Rotor structure selections of nonsine five-phase synchronous reluctance machines for improved torque capability

Five-phase synchronous reluctance machines (SynRMs) have a higher torque density over conventional three-phase SynRMs due to the utilization of the third harmonics in the magnetic field interacting with appropriate armature current. However, for effective utilization of the third harmonics, it is critical that the rotor of the SynRM creates sufficient coupling between the fundamental and third harmonic components in the field. This paper presents a comparison study of the rotor structures for the nonsine five-phase SynRMs with a detailed examination of two different reluctance rotor structures. The comparison results reveal that, with a simple structure, the salient-pole rotor creates strong mutual coupling between the fundamental and third harmonic MMFs and, thus, outperforms the complicated axially laminated rotor structures for nonsine five-phase SynRMs in terms of torque and ease of manufacturing.