Dynamometer Testing and Characterization of Switched Reluctance Motors (SRMs) for Electrified Powertrains

Abstract

The electric vehicle (EV) market is experiencing growth at an exponential rate, forcing automotive manufactures to invest in powertrain electrification. Manufactures are seeking low cost alternatives for electric propulsion motor technologies with switched reluctance motors (SRMs) having tremendous potential. The performance characteristics of SRMs designed for EV propulsion applications have yet to be experimentally verified. In this thesis, the operation of a 24/16 propulsion SRM specifically designed for a hybrid electric vehicle will be verified with a theoretical model and experimentally. The results are analyzed to gain further understanding of the factors affecting propulsion SRM operation. Two distinct theoretical models of a SRM are presented where one includes the effects of mutual coupling between two excited phases. The theoretical models and the experimental results indicate that for high power density SRMs, designed for propulsion applications, the effects of mutual coupling cannot be ignored. The motor is experimentally tested using a dynamometer machine. A test plan is presented which tests the motor at a wide speed and torque range suitable for EV applications. The testing procedure attempts to segregate the motor losses similar to international standards for induction machines and permanent magnet machines; however, these methods prove invalid due to the non-sinusoidal current in SRMs. Torque ripple minimization is highlighted to reduce the risk of detrimental speed fluctuation during motor testing with careful attention to thermal limitations. The SRM is tested using PWM current control as the baseline control method because hysteresis control is proven to be challenging for the tested SRM. The work presents many challenges associated with the testing and characterization of SRMs for propulsion applications; however, new research findings illustrate the potential of future improvements in propulsion SRM design and operation.