Development of a high torque density and efficiency axial flux switched reluctance motor for electric vehicle

Vehicle electrification is fundamental to decrease the pollution generated by circulation and improve the quality of life of urban populations but pure electric vehicle has not been extended so far mainly due to the insufficient energy density of batteries. Another obstacle is the supply of the permanent magnets required by the electrical motors most commonly employed in electric vehicles, as 95% of the global supply is provided by China, generating important supply and cost uncertainties.

With the aim of providing a suitable magnet-free alternative to these motors, the promising, little explored, axial flux switched reluctance technology has been selected in this thesis to develop a high torque density and efficiency motor, suitable for cost-effective mass production.

As suitable tools do not exist for designing this type of machines from scratch, first an analytical sizing and calculation tool has been developed. After a successful validation based on 3D Finite Element simulations and test bench results, this tool has been used for understanding the influence of each design parameter on the static motor performance and providing design guidelines. As a good static performance does not necessarily ensure a good dynamic performance, a dynamic simulation model has also been developed to evaluate the dynamic performance of the designed motors with different control strategies and complete the aforementioned guidelines.

Finally, using the developed tools, a motor prototype has been designed, manufactured, assembled, tested in a test bench, integrated on a commercial electric vehicle and further tested in a commercial vehicle testing platform, obtaining a good correlation among analytical, FEM and experimental results.

The performed work has shown that this kind of axial flux switched reluctance motors can hardly reach the torque density and efficiency provided by high performance permanent magnet motors, but they can offer a better constant power speed range and a simpler, safer, more reliable, cost-effective design.