Permanent Magnet Assisted Synchronous Reluctance Motor with Asymmetric Rotor for High Torque Performance

Permanent magnet assisted synchronous reluctance motor (PMA-SynRM) is a kind of high torque density energy conversion device widely used in modern industry. In this paper, based on the basic topology of PMA-SynRM, a novel PMA-SynRM of asymmetric rotor with position-biased magnet is proposed. The asymmetric rotor design with position-biased magnet realizes the concentration of magnetic field lines in the motor air gap to obtain higher electromagnetic torque, and makes both of magnetic and reluctance torque obtain the peak value at the same current phase angle. The asymmetric rotor configuration is theoretically illustrated by space vector diagram, and the feasibility of high torque performance of the motor is verified. Through the finite element simulation, the effect of the side barrier on output torque and the Mises stress under the rotor asymmetrical design are analyzed. Then the motor characteristics including airgap flux density, back EMF, magnetic torque, reluctance torque, torque ripple, losses, and efficiency are calculated for both the basic and proposed PMA-SynRMs. The results show that the proposed PMA-SynRM has higher torque and efficiency than the basic topology. Moreover, the torque ripple of the proposed PMA-SynRM is reduced by the method with harmonic current injection, and the torque characteristics in the whole current cycle are analyzed. Finally, the endurance to avoid PM demagnetization is confirmed based on the PM remanence calculation.