Comparative Multi-Physics Analysis of Radial Flux PM, Axial Flux PM and Synchronous Reluctance Machines for E-Axle Applications.

Vehicle manufacturers require electric motor manufacturers to develop products that, on the one hand, are increasingly high-performing in terms of power density, and on the other, reduce the use of rare-earth elements for geopolitical, environmental, and ethical reasons. The present thesis work takes place within the activities developed by HPE srl, an engineering company based in Modena. This work aims at the electromagnetic, structural, and thermal design of a high-voltage three-phase synchronous electric motor, intended for a fully electrified axle for automotive applications. Three types of electric machines were designed in order to evaluate their strengths and various critical issues: - radial flux permanent magnet motor: the currently predominant solution on the market, - axial flux permanent magnet motor: allows for maximizing power density, - radial flux reluctance motor: represents a possible alternative for electric mobility with a reduced rare-earth content. The results highlight that the reluctance motor struggles to ensure acceptable performance at higher rotational speeds; conversely, the axial flux machine demonstrates excellent power delivery capabilities alongside low weight. However, compared to the more traditional radial configuration, it requires significantly more complex structural solutions, limiting the space available for the integration of advanced cooling systems. The permanent magnet machines therefore proved to be the most effective for the project targets and underwent thermal validation, pairing each with the most suitable cooling system. Specifically, for the radial geometry, it was possible to implement a high-performance direct cooling system with windings immersed in dielectric oil, whereas for the axial configuration, due to spatial and manufacturing limitations, a more traditional water cooling jacket was chosen. The results of the thermal analysis highlight that the solution featuring radial flux magnets and oil cooling represents the best compromise between performance and ease of manufacturing.