Geometrical Control of Eddy Currents in Additively Manufactured Fe-Si

Additive manufacturing has enabled the processing of high-silicon electrical steels with excellent soft magnetic properties. In bulk form, core losses resulting from eddy currents would be too large to use in high-frequency electrical machines, therefore strategies are needed to reduce eddy currents. Additive manufacturing affords high complexity and provides the opportunity for cross sectional patterns within the material to limit eddy current generation. This study investigates several designs, including a novel hexagonal pattern shown to have the lowest eddy current loss coefficient of 0.0005, less than 25% of the bulk material with an eddy current loss coefficient of 0.0021. Heat treatment is shown to increase the eddy current losses, demonstrating that for high-frequency machines, it may be beneficial to use the as-built state. Physical samples were compared to their intended geometries, showing defects in these complex cross sections causing increased eddy currents when compared to simulations, but geometrical accuracy can be improved by alternative design methodology which experimentally experiences smaller losses. These cross sectional designs may be implemented into an electric machine with a 3D magnetic flux pathway, enabled by additive manufacturing, affording flexibility for electrical engineers to design new motor architectures in the pursuit of higher power density.