Thermal analysis of solid rotor in PMSM used for EV

Abstract

A solid rotor permanent magnet synchronous motor (PMSM) is developed for the electric propulsion part in electric vehicles (EV). The rotor in this kind of motor is composed of splits solid bodies, interior permanent magnets and starting bars. Wedges and bars are shot circuited by end rings that promote the generation of starting torque jointly. While PMSM used in EV, it may need to start frequently at different load, which would cause eddy losses in rotor and related to thermal demagnetization of permanent magnet directly. In this paper, a prototype of 30 kW solid rotor PMSM is proposed, and numerical calculation models for thermal analysis are established. The 2D electromagnetic fields were calculated by using finite element method (FEM) first and motor losses in rotor were determined. From the analysis of fluid analysis of air in airgap, an effective coefficient of heat transfer is proposed to deal with the complex heat exchanges between rotor and stator. Then steady thermal field is analyzed, and influences of motor fan, loads and stray loss on rotor temperature distribution were studied. Some associate test work has been done with results in a good agreement with the analysis data. Some reasonable conclusions were obtained, which can provide some help for the design of this kind of PMSM and its application in EV.