Design of Rare-Earth-Free Electrically Excited Synchronous Motor for Urban e-Logistics Under Specified Driving Cycle

This article presents a time-efficient design process of an electrically excited synchronous motor (EESM) for the use in urban e-logistics such as an Electric Mini Cargo Truck (EMCT). The aim is to develop a rare-earth-free traction motor alternative for urban e-logistics. Considering the driving cycle, the proposed design process utilizes extended scaling laws and Magnetostatic Finite Element Analysis (MS-FEA) to reach the final design of the EESM. The proposed design methodology is applied to a 22 kW EESM with fixed core dimensions. The process involves: 1) deriving the required torque-speed profile based on the New European Driving Cycle (NEDC); 2) conducting parametric analyses to evaluate key motor performance characteristics; and 3) satisfying terminal voltage constraints by optimizing stator winding configurations, including the number of turns and parallel paths, while targeting high-efficiency operating points. The rotor field winding parameters are determined based on voltage level constraints, which are influenced by the design of the contactless power supply (CPS) system that supplies the power the field winding. The designed EESM is manufactured and the electromagnetic performance including the CPS is validated at the design points.