High torque density and low torque ripple surface permanent magnet machines with sinusoidal plus third harmonic shaped magnets

This paper proposes a new surface permanent magnet machine (SPMM) design in which the stator coils are distributed and sinusoidally full pitched with a unity winding factor and the permanent magnets (PMs) are shaped sinusoidally with an added third harmonic component in the axial direction. The proposed design mainly focuses on improving the torque density and minimizing the torque ripple of conventional SPMMs with distributed windings. The choice of this particular PM shape produces a pure sinusoidal and a third harmonic flux linkage and back electromotive force (EMF) without any other harmonics. Not only does the existence of the third harmonic enhance the fundamental component magnitude of the flux linkage, but it does so without producing any additional torque ripple in three phase machines. The performance of the proposed machine is benchmarked against the base-line model 2007 Camry motor and the modified Camry conventional, bread loaf and the sinusoidally shaped SPMMs. The results and comparisons show that the proposed design increases the torque density significantly while the torque ripple is maintained at a minimum level.