Design of Electrically Excited Synchronous Machines to Achieve Unity Power Factor in Field Weakening for Long-Haul Electric Trucks

Electrically excited synchronous machines are a promising candidate for long-haul electric trucks due to excellent capability in field weakening. This study aims at concluding a structural design process of the machine for long-haul electric trucks. A criterion of machine design to achieve unity power factor in field-weakening is derived. With this criterion, a minimum level of field current is decided in the design process. Parametric sweeps are applied to decide the optimum slot geometries for stator and rotor. The optimization of slot geometries is multi-objective. In this study, it is to maximize the peak torque while minimize iron-core losses simultaneously. Pareto frontier is used to identify the optimum solutions. The performance of the finalized design is then evaluated. The high-efficiency area is located at high-speed low-torque region which is preferable for long-haul electric trucks. Balance is achieved between copper and iron-core losses during steady-speed intervals of the test cycles which leads to minimum losses in total.