Design of a Reconfigurable Winding Switch for an In-Wheel Automotive Motor

A design is presented for an electro-mechanical switchgear, intended for reconfiguring the windings of an electric machine whilst in operation. Specifically, the design is developed for integration onto an in-wheel automotive motor. The motor features 6 phase fractions, which can be reconfigured by the switchgear between series-star or parallel-star arrangements, thereby doubling the torque or speed range of the electric machine. The switchgear has a mass of only 1.8kg – around one tenth of the equivalent 2-speed transmission which might otherwise be employed to achieve a similar effect. As well as the extended operating envelope, the reconfigurable winding motor offers benefits in efficiency and power density. The mechanical solution presented is expected to achieve efficiency and cost advantages over equivalent semiconductor-based solutions, which are practical barriers to adoption in automotive applications. The design uses only mechanical contacts and a single actuator, thereby offering a convincing techno-economic proposition. Furthermore, it is shown that a torque interruption time of <30ms is feasible for reconfiguration events using the mechanical relay; whilst this is longer than for a semiconductor-based solution, it is likely to be imperceptible to vehicle passengers and not affect the driver experience. The project outcomes show that mechanical relay designs can in fact provide a competitive all-round solution for this functionality, making reconfigurable motors a realistic prospect for automotive applications.