On-load Back-EMF Optimization Based on the Back-EMF MST Method and Parametric Optimization

This paper proposes an optimal design for a surface mounted permanent magnet synchronous machine (SM-PMSM) based on parametric optimization process in order to reduce the on-load Back-EMF distortions due to the increasement of the electromagnetic load and saturation. Differently from the conventional methods presented in the literature, the optimization approach proposed in this paper accounts for the saturation, air-gap flux density distribution and the on-load Back-EMF assessment by means of finite element analysis along with the most recent method to evaluate the on-load Back-EMF that is known as Back-EMF MST. Furthermore, the optimization process is carried out considering either the physical machine symmetry (based on pole numbers) and a non-evident machine symmetry (based on saturation effects and on the relevance of each tooth on the Back-EMF waveform) that is found thanks to the Back-EMF MST Method. The proposed optimization process also analysis different set of variables based on symmetrical and asymmetrical tooth dimensions. As a result, a reasonably better designed machine is obtained with higher average torque, lower torque ripple and lower volume. In addition, the on-load Back-EMF is almost identical to the no-load one and consequently, the on-load cogging torque is almost identical to the no-load cogging torque.