Current optimization strategy for surface permanent magnet synchronous motor drives based on a rigorous mathematical model

Surface permanent magnet synchronous motors (SPMSMs) have been used for high-performance applications which demand high levels of torque smoothness. This paper presents current optimization strategies to achieve the smooth torque production in SPMSMs. The proposed techniques are based on a newly developed mathematical model which takes into account spatial harmonics of the rotor magnet flux. Based on this model, the smooth torque production can be achieved by adjusting the armature current vector in the rotating frame. Consequently, the waveform of the optimized excitation current is non-sinusoidal. The current optimization algorithm requires low-computational cost. Moreover, the optimized current contributes not only to the torque ripple suppression but also to the winding resistive loss reduction. The effectiveness of the current optimization techniques is confirmed by analytical verifications by using generalized machine models. In addition to this analytical approach, simulation and experimental verifications are implemented in a typical 3-phase SPMSM which has concentrated windings.