Analysis, characterization and minimization of IPMSMs cogging torque with different rotor structures

This paper presents the analysis, characterization and comparison of the cogging torque components generated by five different IPMSM rotor structures. More in detail, an IPMSM model (named IPMSM1), which is derived from a commercial geometry, is analyzed by using a Finite Element Method (FEM) approach. Then, four other IPMSM models, which are obtained by modifying the IPMSM1 rotor structure and by maintaining the same stator configuration, are proposed and analyzed. From the obtained simulation results, the cogging torque components for each structure are determined and compared. From this comparison, a significant cogging torque decrease is occurring for the modified geometries, without affecting the values of the generated torque. Furthermore, a meaningful relationship between the peak values of the cogging torque and the gradients of the flux density around the neutral area is reported and discussed. Therefore, simple structure modifications applied to the rotor geometry can bring significant improvements in terms of motor performances and cogging torque reduction.