Torque ripple reduction of the modular Interior Permanent Magnet machines using optimum current profiling technique

Interior permanent magnet (IPM) motors are widely used in various applications due to many advantages such as high power density, high efficiency, low manufacturing cost and wide constant power operating range. Compared to surface mounted permanent magnet (SMPM) motors, IPM motors have relatively higher torque ripples. The back-EMF voltages induced in the stator windings are not ideal sinusoids. This produces considerable torque ripple when the IPM motors are excited with sinusoidal currents. In this paper, an optimum current profiling technique is presented to minimize the torque ripple along with the copper losses in the stator windings. Analysis shows the simplicity of this optimization technique. Only the back-EMF information and the inductance differences in d-q frame are required, which can be easily obtained by finite element analysis (FEA) without intensive computation. It is shown the torque ripple is significantly reduced when the machine is supplied with the optimum currents.