Synchronous Reluctance Machines (SRMs) have been gaining considerable research interest recently because of the absence of the permanent magnets (no rare-earth materials), their robust construction and high partial load efficiency. Their inherently lower torque density compared to permanent magnet synchronous machines remains a challenge. However, adopting an axial flux topology could potentially improve this feature. This paper analyzes the properties of the axial flux configuration and compares them with those of the traditional radial flux topology for synchronous reluctance machines used in electric vehicles. The paper focuses on the differences in the torque-production, in the efficiency, in the torque densities and in the weight and the physical dimensions. Additionally, this paper examines the material costs for the two machine types and investigates their predicted future prices to determine the more cost-effective solution for electric vehicle applications. Simulation investigations will be carried out to examine these properties. It will be shown that the axial flux topology is an attractive alternative to the nowadays widely used radial flux one in the case of synchronous reluctance machines of electric vehicles.

Synchronous reluctance machines offer a cost-effective alternative to the nowadays widely used permanent magnet synchronous machines in applications that require high partial-load efficiency. Pumps, fans, compressors and electric vehicle drive systems are all good examples for such applications. Synchronous reluctance machines do not need any permanent magnets for the torque-production, which means that they are not affected by the drawbacks related to them. The nowadays most widely used permanent magnets are based on rare-earth minerals, which present significant supply chain issues, burdened by severe geopolitical tensions. These difficulties can all be eliminated by using synchronous reluctance machines, while offering high partial-load efficiency. The utilization of the axial flux topology enhances the torque density, further increasing the attractiveness of these machines. However, it is important to analyze the other possibilities to improve the characteristics of the machine to make them even more appealing in the case of electric vehicle applications. Such an option is to apply an aluminum winding instead of a copper-based one. This paper presents an investigation for the application of the aluminum winding to improve the most important characteristics of the Axial Flux Synchronous Reluctance Machines (AFSRMs). Simulation examinations will be carried out to analyze the potential possibilities to enhance the characteristics of the machine. It will be shown that the aluminum winding requires an alternative design to achieve improvements over the copper-based one in the most relevant attributes. Also, it will be shown that with the appropriate design the aluminum-winding-based AFSRM is able to outperform the copper-winding-based one, offering a significant cost-advantage with only a minor compromise in the geometrical dimensions of the machine, which is an acceptable compromise in the case of an electric vehicle application.