Modeling and analysis of SynRM for hybrid electric vehicle application

Abstract

In this thesis, the performance of a 4-pole SynRM is evaluated and compared to a reference 8-pole PMSM of the same size, where the machines are used in a hybrid electric vehicle (HEV) application. In order to perform a performance comparison between the machines, a design of the SynRM rotor is developed. The design is determined by using two different Mathematical Models that provides the size and position of the rotor air barriers and iron segments. The final comparison between the SynRM and the PMSM shows that if the machines operates with the same current density in the stator windings, the average torque produced by the SynRM is approximately one third of the torque produced by the PMSM. If both machines are run with the same stator current, the average torque produced by the SynRM is slightly less than half of the torque in the PMSM and the torque ripple can be reduced to levels similar to the ones in the PMSM. The low performance is mainly due to rapid saturation along the d-axis, therefore, making the current angle one important factor. The efficiency is also slightly lower in the SynRM compared to the PMSM. As expected, when the machine is operated along the MTPA line, it shows improvement in efficiency and reduction in losses. The efficiency of the SynRM is only a few percent less than the efficiency of the PMSM. Overall, more study is needed in the field, mainly to see how an increased size and proper control affects the system. But also to see what impact higher insulation ratios have on the machine. The alignment of the air barriers in the rotor against the stator slots is the single variable that effects the torque ripple the most. The SynRM also shows signs of saturation for low current, an issue that probably can be handled by the use of control strategies such as the MTPA combined with an increased rotor diameter. The saturation issue may also be reduced if it is being considered when developing a rotor design. Overall, the results in this thesis indicates that the SynRM is not a valid replacement for the PMSM in HEV applications with the design presented in this thesis.