Torque Enhancement of Surface-mounted Permanent Magnet Synchronous Machines via Axial Assisted Magnets

A torque enhancement scheme using axial assisted magnets for surface-mounted permanent magnet synchronous machines (SPMSMs) is proposed in this paper. It divides the total permanent magnets into two parts viz. main magnets mounted on the rotor surface, and assisted magnets in the axial direction, with the restriction of the same volume of magnets. According to the theoretical derivation and the finite element (FE) analyses, the proposed design can effectively enhance the output torque after a reasonable combination of the size parameters of main and assisted magnets, while the machine outer size, armature winding current, and volume of total permanent magnets are the same as the conventional SPMSM. The optimal results, average torque increased by over 6.2% without sacrificing torque ripple, of the proposed machine are obtained with the sequential optimization and validated by the experiments.