Design of an axial flux machine for an in-wheel motor application

Abstract

This master thesis deals with the design of an axial flux machine for an inwheel motor application. Four double-sided axial flux machine topologies are compared to select the most suitable one for designing a high torque density machine that fits into a predefined geometry (diameter: 260 mm, length: 72.5 mm). The yokeless and segmented armature (YASA) topology is chosen, due to its very compact structure. The design is made by using analytic and 3D finite element analysis alternately. The geometry of the electromagnetic circuit is optimized to find the maximum rated torque (≈80 Nm) for proposed values of magnetic flux and current densities (1.7 T and 7 A/mm2). These densities are chosen with the intension of reaching a high utilization of both the copper and the iron in the machine, when their proportions are determined by the maximal product of electric and magnetic loading. When the geometry of the electromagnetic circuit is determined, it is held fixed. Possible different torque speed characteristics of the machine are then investigated, with respect to current and voltage limitations together with the turn selections of the windings. A final design is proposed and its theoretical characteristics are evaluated and presented. The power density, at 2400 rpm and 7 A/mm2, is calculated to 5.3W/cm3. Furthermore, some suggestions for future work and modifications are made.