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

TL;DR

This study explores the use of soft magnetic composites in wound field synchronous machines for automotive traction, achieving higher efficiency and cost benefits without rare-earth materials.

Contribution

It introduces a novel SMC-based rotor-stator design for radial EESMs, improving efficiency and reducing reliance on rare-earth materials in automotive applications.

Findings

Achieved 89.7% efficiency over WLTP cycle, 1.4% higher than reference PM machine.

Optimal configuration uses SMC in stator and 0.35 mm NO35 laminated steel in rotor.

Eliminates rare-earth materials and reduces costs with thicker laminations.

Abstract

This paper investigates the application of soft magnetic composites (SMCs) in the stators of wound field synchronous machines for automotive traction. While SMCs are traditionally employed in axial flux topologies, this study examines their use in radial-flux electrically excited synchronous machines (EESMs). Multiple SMC materials and lamination thicknesses are evaluated, with the optimal configuration combining a SMC material in the stator and 0.35 mm NO35 laminated steel in the rotor. This combination delivers improved torque and efficiency compared to conventional designs. When integrated into a full electric drive unit (EDU), this motor achieves 89.7% efficiency over the WLTP drive cycle, representing a 1.4 percentage point improvement over a reference permanent magnet synchronous machine-based EDU. The proposed solution eliminates rare-earth materials, reduces cost through thicker laminations, and offers environmental benefits through SMC utilization. This novel material combination, previously unexplored for radial EESMs, presents a promising direction for affordable, high-efficiency, rare-earth-free automotive traction machines.