A Review of Motors with Reconfigurable Windings for Automotive Traction Drives

This paper provides an overview of the application of reconfigurable windings in traction motors and their prospective benefits for electric vehicles. Methods of implementation discussed are series–parallel, star-delta, and tapped windings with series-parallel configurations having the greatest potential for system performance improvements. The review provides valuable insights into the impact on e-drive system mass and volume, showing significant improvements to torque and power densities of approximately 40-80% can be achieved. Other investigations targeting motor efficiency show total motor loss reductions of approximately 30-60% are also possible. The published literature on the topic tends to be case-specific, indicating that the generalisation of the technology applicability is lacking, with a particular need for design tools and methodologies early in the propulsion system design stage, to explore how the technology could be best applied. This is also highlighted by the system level impacts shown in a case study on the Nissan Leaf drive, with series-parallel reconfigurable windings resulting in a 41.67% inverter current reduction while maintaining baseline performance characteristics. Other key challenges to the technology uptake include the cost and complexity of the reconfiguration device, however If these can be overcome, and the design advantages better understood, traction drives with reconfigurable windings show potential in reducing the size, weight, and cost of the electric machines, while improving their efficiency and power density.