Saliency Ratio Based Torque Enhancement of Switched Reluctance Motor for EV Application /

Abstract

The EV market is developing sharply with an increased demand for reliable, efficient, and economical power trains. To achieve greater performance, the EVs typically employ Brushless, Induction, and Permanent magnet (PM) synchronous motors. Although, both the SRM and PM motors offer improved efficiency. However, the magnets in these motors have high market cost volatility and reliability issues due to the demagnetization of magnets from excessive heat at continuous operation. Switched reluctance motor (SRM) is a viable alternative, as it works without magnets, is more robust, fault-tolerant, and reliable. However, switched reluctance motors are facing challenges in achieving high performance in terms of power factor, torque per ampere and torque ripples. There are a number of parameters that have varying impact on the machine performance and one of them is magnetic saliency. This work presents complete design of a mid drive electric motor from scratch with drive for high performance electric bike. Switched reluctance motor is selected due to its recognized benefits for Electric Vehicle applications. A systematic methodology is adopted to estimate power rating for desired vehicle performance that includes calculation of the vehicle mechanical and aerodynamic parameters. Geometrical, operational, and electrical parameters are determined. Two motors configurations with different number of rotor poles are designed. Magnetostatic analysis is performed to check static torque generated with the designed geometries. Parametric analysis is done on one of the motor while keeping the same fill factor and electrical loading to get improve torque profile. Then 2D FEM Magnetostatic and 2D transient analysis is performed in Ansys Maxwell. Different performance parameters like efficiency, Avg Torque, torque ripple, and losses are evaluated and compared. The results shows that the SRM with higher rotor poles is a better choice.