Continuous Hairpin Winding Technology for Electric Machines Enabling Net Zero Transportation: A Comprehensive Review

Featured by low power losses and strong heat dissipation capability, hairpin winding has been widely accepted as a key enabler of boosting performance for traction/propulsion electrical machines in automotive and aerospace sectors. Continuous hairpin winding (CHW), distinguished by its further improvement brought to machines’ key performance indicators, being power density, efficiency, and reliability, is emerging as a more promising winding solution. This paper will provide a critical technology review on CHW, with focus on highlighting its different features compared with those of other typical winding types, manufacturing/assembly process, layout design rules, as well as current and future development trends. Based on illustration of the unique winding process, the so-called “radial shift” feature that inherently exists in CHW will be introduced. The key elements in winding layout development, including transposition, terminal and jumper connections, parallel branch number, will be summarised for CHW. Moreover, new technology bricks and research ideas that strive to tackle manufacturing challenges, enhance design flexibility, as well as improve overall performance have been highlighted. Finally, the paper concludes by proposing future research directions, with the vision of increasing its Technology Readiness Level (TRL) for future net-zero transportation.