Minimization of higher back-EMF harmonics in permanent magnet motor using shape design sensitivity with B-spline parameterization

This paper presents a shape optimal design method for reducing the higher back-EMF harmonics generated in the permanent magnet motors, in which torque ripples could occur. The continuum shape design sensitivity formula and the finite element method are employed to calculate the sensitivity of flux-linkage to the design variables, which determine the shape of iron pole piece. The design variables are optimized with a B-Spline parameterization in order to provide the back-EMF waveform as close as possible to a sinusoidal form. The design algorithm is applied to a three-phase interior permanent magnet motor that contains a mount of higher back-EMF harmonics.