Influence of the Slots Number Combinations among the Inner and Outer Stator on Torque Ripple in Dual-Stator Permanent Magnet Synchronous Motors

Low-speed-high-torque permanent magnet synchronous motor (LSHTPMSM) is widely used in industrial applications. However, the torque density of conventional LSHTPMSMs is not ideal, which limits their further applications. The PMSM with dual-stator is proposed to improve the torque density of LSHTPMSM. To obtain a stable output torque of PMSMs with dual-stator, this paper investigates the influence of the slots number combinations among the inner and outer stator on torque ripple in dual-stator permanent magnet synchronous motors (DSPMSM). In this paper, five combinations are exemplified for the DSPMSM. Firstly, the inner and outer stators, with the rotor from the DSPMSM, are divided into two separate motors. Then, the results of the output torque of DSPMSM with these five combinations and the separate motors are obtained by FEM. Comparing the results, it can be seen that the torque ripple of the separate motors adopting different stator slots numbers differs in phase, which makes the torque ripple of the whole DSPMSM differ. Finally, aiming at obtaining a lower level of the torque ripple of the whole motor under the optimal combination, injection of the harmonic currents in the outer stator windings is utilized.