Torque Ripple Reduction and Mechanical Tolerance Analysis of A Novel Dual-Stator 6/4 Flux-Switching Permanent Magnet Machine

The purpose of this paper is to investigate both the torque ripple reduction technique and influences of mechanical tolerance on the performances of a novel dual-stator 6/4 flux-switching permanent magnet machine. To minimize the torque ripple, step skew designs are studied to determine the optimal step number and step skew span angle. In addition, three common rotor mechanical tolerance deviation cases are analyzed to investigate their influences to the machine performance. These cases include the deviation of offset angle between the front and rear rotor poles, rotor static eccentricity, and rotor dynamic eccentricity. 3-D finite element analysis reveals that the most practical design is the optimal two-step skew design, which significantly reduces the torque ripple while maintaining a sufficiently large average torque compared to the initial design without step skew. It is found out that the mechanical tolerance variation of offset angle significantly impacts on the harmonics of back-EMF. The torque ripple and rotor unbalanced magnetic forces are substantially influenced by the tolerance of the rotor static or dynamic eccentricities.