Improvement torque performances of interior permanent-magnet machines

Due to their excellent efficiency, power density and constant power speed region, interior permanent-magnet (IPM) machines are very suitable for electric vehicles (EVs). This paper proposed a new IPM rotor topology, which can offer high reluctance torque, wide constant power speed range and excellent overload capability. Besides, five rotor topologies with integral-slot distributed-windings IPM machines, including four existing IPM topologies and the proposed IPM topology, are designed optimally. Their characteristics, which include d-q axis inductances, saliency ratios, electromagnetic torques, corresponding torque ripples, back-electromotive forces (EMFs), overload capabilities and flux weakening performances are evaluated quantitatively. Finally, a three phase 48s8p hybrid rotor PM machine is built to verify the performances of the proposed IPM machine. This work provides some general concepts for machine developers who are willing to build IPM machines for high-performance EV applications.