Design and Performance Analysis of a Novel Permanent Magnet Synchronous Motor with Stepped Magnetic Poles

This paper proposes a novel permanent magnet synchronous motor (PMSM) with stepped magnetic poles to improve utilization of the rare-earth PM material without deteriorating the torque performances. Initially, the simplified model is introduced for elucidating the air gap flux density generated by the proposed stepped PM topology. The relationship between the parameters of the stepped magnetic poles and the air gap flux density is analytically derived and confirmed. Subsequently, the parameters of the stepped magnetic poles are optimized to minimize PM consumption while achieving the desired fundamental harmonic of air gap flux density. Furthermore, the skew slot is adopted to mitigate torque ripple. Electromagnetic performances of the two machines, including no-load characteristics and torque characteristics, are analyzed and compared by finite element analysis (FEA). It is found that the proposed motor can reduce the permanent magnet by 5.1% under the premise of generating the same electromagnetic torque, and the torque ripple is also reduced. Finally, the proposed stepped PMSM is prototyped and measured to validate the analysis.