Design and Implementation of a Low Power Outer-Rotor Line-Start Permanent-Magnet Synchronous Motor for Ultra-Light Electric Vehicles

Abstract

Recently, while electric vehicles (EV) have substituted the fossil fuel vehicles, the design of the electrical motors with more efficient and less mechanical converters has become mandatory due to the weighting gears, mechanical differentials, and other cost-increasing parts. To overcome these problems, double electrical motors with low speed and high torque have been designed and used in the rear wheels of the EVs without any gearbox and mechanical differential. In this study, a novel outer rotor line-start hybrid synchronous motor is proposed as another solution. For this aim, four different hybrid rotor types, including magnets and rotor bars, have been designed and analyzed. Calculation and estimation of all parameters to design a motor are introduced. All of the analyses were carried out by Finite Elements Method (FEM). One of the analyzed motors, which is called Type-D was selected and implemented because of the best startup performance and better steady-state behavior under the rated load and overload. While holding this motor at synchronous speed under nominal load, in case of overloading, it remained in asynchronous mode, thus maintaining the sustainability of the system. Obtained results prove that the newly proposed outer rotor LSSM has the advantages of both synchronous motor and asynchronous motor. All of the experimental results validate the simulations well. The effects of the magnet alignments and dimensions on the performance of the motors are presented.