Engineering considerations on skewing of an interior permanent magnet synchronous machine for parallel hybrid electric heavy vehicles

The focus of this paper is on investigating the influence of skewing on the torque production of an Interior Permanent Magnet Synchronous Machine (IPMSM). The machine is designed as a traction machine according to the requirements of a parallel hybrid electric commercial heavy vehicle. In order to meet the requirements, the machine is designed with a speed higher than that of the conventional powertrain and connected via a fixed speed reduction. To minimize the noise and wear in the gear reduction, it is desirable to keep the torque ripples in the machine to a minimum. The investigation is performed in the post processor of a 2D FE simulation tool. The outcome from the study is that skewing has higher influence on the fundamental torque when operating in field weakening compared to below base speed. This makes skewing questionable as a mean to reduce the torque ripple in an IPMSM traction machine. The simulation result is verified with measurements with good correlation.