Novel reluctance axis shifted machines with hybrid rotors

This paper proposes a novel reluctance axis shifted (RAS) machine with hybrid rotors, i.e., permanent magnet (PM) and synchronous reluctance parts, respectively. The proposed design is geometrically characterized by two axially parallel rotors, which enables the full utilization of reluctance and magnet torque components for torque improvement. In the proposed design, the reluctance axis coincides in phase with the magnet axis by shifting the rotor in the PM-free synchronous reluctance machine (SynRM) part. Hence, the magnet and reluctance torque components reach the maximum in the same current phase so as to maximize the output torque. Meanwhile, the surface-mounted PM (SPM) configuration can well address the manufacturing, torque ripple and mechanical vibration issues existing in the conventional PM-assisted SynRMs and other conventional interior PM (IPM) machines. Moreover, the dual parts can be autonomously designed, which gets rid of the severe cross-coupling effect in those IPM machines. In this paper, the machine structure and torque maximization mechanism are described, respectively. In addition, the proportioning of the PM and SynRM parts is optimized to maximum the average torque. Finally, the electromagnetic performance of the optimized structure is compared with that of a conventional Prius 2010 IPM machine to highlight the advantages of the proposed design.