Rare-Earth Free Unity Power Factor Bi-Axial Excitation Synchronous Machine for Traction Applications

• Published in: IEEE transactions on industry applications Vol. 60; no. 4; pp. 5966 - 5978
• Main Authors: Chattopadhyay, Ritvik, Jung, Junyeong, Islam, Md. Sariful, Boldea, Ion, Husain, Iqbal
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Air gaps; Coils (windings); Demagnetization; Electric vehicles; Excitation; ferrite magnets; Finite element method; Magnets; Power factor; Prototypes; Rare earth elements; rare-earth free; Reactive power; Rotors; Stator windings; Supply chains; Synchronous machines; Topology; Torque; Traction; traction motor; Two dimensional analysis; Unity; unity power factor; Windings; wound field synchronous machine
• ISSN: 0093-9994; 1939-9367
• DOI: 10.1109/TIA.2024.3379312

Rare-earth-based traction machines are subject to supply chain, geo-political, and price fluctuation issues, which makes rare-earth-free motor topologies attractive for electric vehicle (EV) traction applications. In this research, a 24-slot/4-pole, unity power factor, air-cooled, rare-earth-free bi-axial excitation synchronous machine (BESM) with ferrite magnets is explored for traction applications. The proposed machine achieves a unity power factor due to the presence of stator flux countering magnets embedded in the rotor, while the torque-producing component of the rotor flux is produced by DC field windings. A 4.2 kW, 40 Nm BESM is designed using a 2D-finite element analysis (FEA) based optimization, and a prototype is fabricated. The performance of the prototype is experimentally verified up to the rated torque in a dynamometer test setup. Based on the experimental validation of the prototype, a scaled-up 100 kW BESM is designed and characterized using FEA to verify the effectiveness of the proposed concept for high-power traction applications.