Electric Machine 3D FEM Modeling and Design Impact on Torque Ripple

Abstract

A Gmsh mesh model of the Prius 2004 IPMSM was established using Gmsh builtin programming language; all geometrical entities, mesh properties, and boundary conditions were defined programmatically in scripts. Depending on the pole-slot combination, a slice model can be conveniently generated by specifying the number of circumferential sections as a constant parameter in the scripts. Furthermore, no-skew and two types of skewed rotor configurations of Prius IPMSM 2004 were simulated in Ansys Maxwell 2. The results showed that both torque ripple and cogging torque were improved under skewed configurations. Comparing with the no-skew rotor, the torque ripple reduced from 30.6% to 12.2% in Herringbone(known as V-shape) and 11.9% in the linear skew design; in terms of cogging torque, it reduced from 1.1 Nm to 0.8 Nm in Herringbone and 0.6 Nm in the linear skew. Cross-validation between Ansys Maxwell 2D and ElmerFEM 2D demonstrates that back-EMF and flux linkage were in good agreement, confirming the reliability of the Elmer setup for the Prius motor. Finally, the ElmerFEM 3D results showed good agreement with the 2D results in terms of back-EMF harmonic content. In particular, the 11th and 13th harmonics were significantly reduced with a skewing angle of 3.75°, while the fundamental magnitude remained nearly unchanged.