Torque Ripple Reduction of Permanent Magnet-Assisted Synchronous Reluctance Motors Based on Equivalent Slotting Effect and Auxiliary Flux Barriers

The salient feature of the rotor structure contributes to a significant torque ripple in permanent magnet-assisted synchronous reluctance motors (PMaSynRMs). The electromagnetic torque output characteristic is closely associated with the air-gap magnetic flux density. The presence of flux barriers (FBs) and the magnetic saturation effect in magnetic bridges (MBs) induces a modulation phenomenon on the air-gap magnetic flux density, which is referred to as the equivalent slotting effect in this study. First, this article proposes an equivalent slotting effect function to reveal this modulation phenomenon and verifies the effectiveness of this function. Second, the insertion of auxiliary FBs into the rotor structure is proposed to mitigate torque ripple in a PMaSynRM prototype based on the equivalent slotting effect. The efficacy of the proposed method is validated through finite element method (FEM) analysis across diverse operational conditions. Third, the mechanism of the proposed method is elucidated by an analytical model (AM) of electromagnetic torque comprising the equivalent slotting effect. Finally, the accuracy of the FEM model is verified through both no-load and on-load experiments. The proposed equivalent slotting effect function is suitable for parametric studies of the rotor structure during the initial design and optimization phase of PMaSynRMs.