High Speed Efficiency of In-Wheel Electric Machines with Star-Delta Reconfigurable Windings

In-wheel electric machines are a desirable form of propulsion for lightweight electric vehicles, however the torque capability and speed range is often compromised due to the fixed gear ratio and volume/mass constraints from packaging the motor within the wheel of the vehicle. Actively changing the winding configuration of an electric machine during operation can be leveraged to enhance the torque capability, speed range, and efficiency of electric machines; the characteristic performance of which can be likened to that of a mechanical gearbox. Reducing the flux linkage of a permanent magnet synchronous machine through winding reconfiguration from star to delta can significantly improve high speed efficiency, with a 32.78% reduction in total loss without detriment to low speed torque capability. This translates to a potential 5.43% reduction in total energy consumption over a real-world drive cycle of a solar powered electric vehicle. Improving drive cycle efficiencies for lightweight electric vehicles highlights a more sustainable transportation option for climate change mitigation strategy.