Design of a 35 kW Permanent Magnet Synchronous Motor for Electric Vehicle Equipped With Non-Uniform Air Gap Rotor

This article presents a successful design of a 35kW U-shaped interior permanent magnet synchronous motor (IPMSM) developed for electric vehicles. An improved rotor with non-uniform periphery based on the eccentricity principle is adopted to make the minimum air gap length appear on the
d
-axis and the maximum on the
q
-axis, thereby improving electromagnetic performance characteristics. Starting from the influence coefficient of this non-uniform air gap, a no-load air gap magnetic field analysis method based on magnetic potential permeance method is established. Afterwards, a two-segment Taguchi optimization model coupled with variable interaction analysis is innovatively proposed. This model optimizes non-uniform rotor periphery and other crucial dimensions for further performance improvement. The effectiveness of this no-load magnetic field analysis method is validated by a series of prototype tests and simulation results. Many simulation analyses of finite element method (FEM) and computational fluid dynamics highlight advantages of the designed IPMSM by comparing its performance indexes with those of the IPMSM with conventional rotor. Simultaneously, the advanced nature and rationality of improved optimization model is also well proven. In addition, operational reliability evaluation including demagnetization and mechanical strength is also implemented to verify the rationality of this design.