HC-04 Multiphysics Analysis of Traction Motors Considering Electromagnetics and Mechanical Factors

Abstract

This paper presents the design and analysis of electric vehicle (EV) traction motors and explores the performance limit using electromagnetic and structural simulations. The interior permanent magnet (IPM) motor for EV traction takes advantage of reluctance torque that is required for flux weakening operation at high speed. However, the complex rotor structure makes it structurally weaker. Therefore. It is likely that the rotor would be subject to mechanical failure and may not reach the required electromagnetic performance. This also indicates that there is a contradiction between electromagnetic performance (e.g., torque, speed, efficiency) and structural strength and there should be a trade-off design to maximum the performance and reliability. In this research, three different rotor designs are considered, from the weakest to the strongest. The electromagnetic analysis is first conducted for the IPM motors such that the calculated output torque, speed, and flux density in air gap are used for electromagnetic characteristic evaluation. The force density in air gap by considering the flexibility of the rotor and stator is obtained for a co-simulation to further calculate the rotor expansion, air-gap length and stress for the three designs. The magnetic force and centrifugal force are both considered. From this analysis, the performance limit of the IPM machine can be explored and a tradeoff between the electromagnetic performance and mechanical strength can be achieved.