Investigation on the Steel Sheet Subdivision and Orientation Potentials of an Axial Flux Machine

A double-sided axial flux machine with a yokeless and segmented armature (YASA) can be manufactured with soft magnetic composite materials (SMC) or different configurations of steel sheet packages for the guidance of magnetic flux in three dimensions. However, these approaches exhibit disadvantages regarding magnetic properties or geometric freedom. Therefore, a novel approach to set up the soft magnetic stator core is simulatively investigated. Instead of constructing the core segments from a continuous sheet metal package, it is to be constructed from several differently oriented sheet metal packages. To evaluate the theoretical potential of this approach the subdivisions and directions of the steel sheets in the tooth tip of the stator are varied and the influences on the torque and the iron losses of the machine are investigated by numerical magnetic field simulation. For the simulation each steel sheet package is modelled as a homogenized region with anisotropic material properties and the iron losses are computed in post processing using Bertotti parameters and considering alternating, rotational magnetization as well as the DC offset of the magnetic flux density. A genetic multi objective algorithm is used to find the Pareto front of the two objectives (torque and iron losses). Moreover, the torque ripple of the final Pareto front is computed and analyzed, showing a configuration with a minimum of torque ripple. In addition to that several tooth tip concepts on the Pareto front are discussed. In general, the tooth tip concepts with many horizontal steel sheet segments at the considered speed have advantages regarding both optimization goals. The stacking factor of the steel sheet package has a strong influence on the ability to guide the magnetic flux of each configuration.