Redução do cogging torque por meio da otimização da segmentação dos polos na máquina síncrona de ímãs permanentes no rotor

Abstract

This work presents an application of an optimization technique in the pole segmentation of permanent magnet synchronous machines with the purpuse of minimizing the cogging torque by acquiring optimal design parameters of the machine. As will be presented pole segmentation has a negative impact regarding the reduction of airgap flux density, which decreases the average value of the developed torque. The behavior of the airgap flux density is then modeled considering the distribution of magnet segments and the angular position of the rotor. After obtaining the flux distribution function model, the analytic expression of the cogging torque derived. Due to a lack of studies regarding pole segmentation applied to rectangular shaped magnets, the behavior of airgap flux density is deeply investigated and the results are presented in this work. Three different optimization scenarios are proposed.The first one considers all pole segments (arc shaped) having equal space between them as well as having same dimensions. The second one considers the possibility of different dimensions and different distances between them. Finally, to analyse the efficacy of the usage of rectangular segments, they are submitted to an optimization process and the results are compared to those with arc shaped. The proposed mathematical models, as well as the optimization proposals, are validated by means of finite elements analysis, where the results are compared to the reference (non-segmented rotor). It is observed a several reduction in the cogging torque peak values in all methods, up to 84%. The application of an optimization process has ensured the preservation of the airgap flux density in all cases, with the best case maintaining 96% of the reference flux density. It is worth mentioning that the usage of rectangular magnets achieved satisfactory results proving to be a suitable option in segmentation, with reduction of cogging torque up to 79%, and preserving 91% of the reference flux density.