Critical Review of Direct-Drive Electrical Machine Systems for Electric and Hybrid Electric Vehicles

• Published in: IEEE transactions on energy conversion Vol. 37; no. 4; pp. 2657 - 2668
• Main Authors: Cai, Shun, Kirtley, James L., Lee, Christopher H. T.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Automobiles; Differential gears; Direct-drive; electric vehicle; electrical machine; Electrification; Fossil fuels; Fuel storage; Gearboxes; Hybrid electric vehicles; Hybrid systems; in-wheel motor; Induction motors; Mechanical transmissions; Passenger comfort; permanent magnet machine; Permanent magnet motors; Propulsion systems; Reduction gearboxes; Rotors; Synchronous motors; Traction motors; Wheels; Windings
• ISSN: 0885-8969; 1558-0059
• DOI: 10.1109/TEC.2022.3197351

With ever-increasing concern of fossil fuel storage and environmental pollution, transportation electrification has recently attracted extensive attention. In conventional propulsion systems, the engine is connected to the wheel through a clutch, reduction gearbox, and mechanical differential. The mechanical transmission inevitably results in power loss, noise, vibration, and additional maintenance. With elimination of the gearbox and transmission component, the direct-drive technique exhibits significant advantages of higher systematic efficiency, more flexible wheel control, and better passenger comfort. This paper aims to provide an overview of automobile direct-drive techniques and recent electrical machine developments for direct-drive propulsion systems. Benefits and limitations of various direct-drive machines are summarized and compared with typical industrial products. Finally, the opportunities, challenges, and future development trends are discussed in related to the research "hot spots".