Dear Colleagues,

With the global drive of pursuing “Net Zero”, electrification has been making remarkable waves in the automotive industry. Many countries have set timelines to terminate the sales of conventional vehicles within the next decade. These ambitious commitments translate to significantly improved performance requirements on powertrains in pure/hybrid electric vehicles, at the very heart of which there is the electrical traction motor. Permanent magnet (PM) motors based on heavy rare earth PM materials have been widely recognized as state-of-the-art traction motor solutions due to their high efficiency and power density. A trend of traction motor development towards higher speed, higher power density, higher voltage and lower cost increase the need to incorporate and develop new machine technologies. Furthermore, the global supply chains of PM motors are facing ever-increasing challenges due to price volatility and limited availability of heavy rare-earth magnet materials. Therefore, the development of PM-free or rare-earth-free PM electric motors for EV applications is becoming more and more appealing.

PM-free motors, such as induction motors (IMs) and switched reluctance motors (SRMs), are being extensively investigated in the literature. Other potential alternatives include synchronous reluctance motors (SynRMs) and wound rotor (WR) synchronous motors, possibly assisted by permanent magnets (PMs) with lower grades. In order to meet the requirements of high power density for these non/less rare-earth PM motors, the design challenges might be significantly increased complexity of machine topology and multi-dimensional interdisciplinary constraints, such as electromagnetic, mechanical, thermal insulation, and control strategy. Therefore, the Special Issue aims to collect original research and review articles on different design and control methodologies or solutions for PM-free or rare-earth-free PM motors targeting for EV applications. The topics of interest include but are not limited to the following:

1. Novel PM-free or rare-earth-free PM machine topologies;
2. Anti-demagnetization techniques for traction motors with lower grade magnets;
3. Design and optimization methods for traction motors;
4. Multi-physical analysis of motors with complex structures;
5. New design techniques for traction motors;
6. Control techniques to achieve high flux-weakening capability or overload capability;
7. NVH optimization and torque ripple suppression methods.

Prof. Dr. Yawei Wang
Dr. Tianjie Zou
Guest Editors

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