Multi-objective tradeoffs in the design optimization of synchronous reluctance machines for electric vehicle application

The synchronous reluctance machine (SynRM) can be considered as a viable alternative to permanent-magnet synchronous machines and induction machines. The absence of permanent magnets or excitation windings are advantages. Additionally, higher efficiencies respectively torque densities are possible compared to induction machines. Lower power factors (typically less than 0.7-0.8) and therefore larger inverter currents are one of the major drawbacks of the SynRM. This paper presents a design optimization procedure for synchronous reluctance machines for electric vehicle application and discusses the tradeoffs between the most important design objectives. The optimization problem is solved using a multi-objective evolutionary algorithm (differential evolution) assisted by a surrogate model (Kriging). This work aims at presenting an approach which is more comprehensive than usual due to the consideration of electromagnetic, thermal and mechanical aspects.