Investigation of Wound Field Synchronous Machines using Soft Magnetic Composites for Automotive Applications

A team led by Andreas Carlsson at Chalmers University has published a study on using soft magnetic composites (SMCs) in the stators of wound field synchronous machines (WFSMs) for electric vehicle traction. Unlike traditional permanent magnet synchronous machines (PMSMs) that rely on costly rare-earth materials, this approach uses electrically excited rotors combined with SMC stators—a material typically reserved for axial flux designs. The researchers evaluated multiple SMC formulations and lamination thicknesses, ultimately finding that a SMC stator paired with a rotor made of 0.35mm NO35 non-oriented electrical steel delivered the best performance.

When integrated into a full electric drive unit (EDU), this motor achieves 89.7% efficiency over the WLTP drive cycle—a 1.4 percentage point improvement over a reference PMSM-based EDU. The switch eliminates rare-earth materials entirely, reduces manufacturing cost through thicker laminations, and leverages SMCs' environmental benefits (lower eddy current losses, simpler assembly). The work demonstrates a novel material combination previously unexplored for radial-flux electrically excited synchronous machines, offering a promising path toward affordable, high-efficiency, sustainable EV traction systems.