Design and Optimization of Hybrid Excitation Synchronous Machines With Magnetic Shunting Rotor for Electric Vehicle Traction Applications

In this paper, a hybrid excitation synchronous machine (HESM) with magnetic shunting rotor is designed for electric vehicle traction applications with consideration of electromagnetic performance and mechanical strength. The HESM with magnetic shunting rotor is a topology of brushless HESM with extended magnetic bridge to embed field windings. The rotor core extends along the axial direction and the increase of rotor length is inevitable, which reduces torque density. In order to improve torque density, the excitation structure is optimized by built-in field windings and the HESM with one-end built-in field windings is presented. To improve the flux regulation capability and decrease the magnet consumption further, the HESM with dual-end built-in field windings is proposed and investigated. The comparative study of the performances of the original HESM and the HESMs with one/dual-end built-in field windings is carried out by three-dimensional finite element method (FEM). An original HESM prototype and a permanent magnet synchronous machine prototype have been developed and the experimental results, which agree well with the FE-predicted results, confirm the advantages of HESM and the validity of FEM used in predictions in this paper.