Torque Improvement of Interior Permanent Magnet Synchronous Machine by Axial-Assisted Magnets

In this article, a torque improvement scheme based on using the combination of main and axial-assisted magnets (AAMs) in rotor is proposed for interior permanent magnet synchronous machines (IPMSMs), which can achieve higher output torque after dimension optimization by both Taguchi iterative optimization method (TIOM) and finite element (FE) analysis. Compared with the conventional IPMSM (CIPM) rotor, this design can achieve higher flux density in the main flux path under the premise of using the same total volume of magnet material, which benefits from the raised working point of permanent magnets (PMs) and reduced PM leakage flux. To verify its effectiveness, the conventional and proposed IPMSM rotors with three types of AAM configurations, i.e., I-shape, V-shape, and U-shape PMs, are fabricated and tested for comparison. It shows that compared with the CIPM rotor, the proposed scheme can achieve a maximum of 8.0% increase in output torque with a quite slight increase in the torque ripple.