Loss performance of an additively manufactured axial flux machine stator with an eddy-current limiting structure

AC electrical machines have mostly been limited to 2D magnetic circuits due to the use of electrical-steel laminations, however, in recent years advances in non-traditional motor architectures such as axial flux show promise for increased torque and power densities. 3D magnetic circuits as required by axial flux motors are difficult to manufacture using laminations, and for other architectures impossible. Soft magnetic composites enable 3D flux pathways but at the expense of magnetic properties. In this study, an axial flux stator is fabricated from high-silicon electrical steel (Fe-6.5 wt%Si) using additive manufacturing with Hilbert cross-sectional geometry to limit eddy current losses and compared with electrical steel laminations of 0.127 mm and 0.35 mm. This shows comparable performance between the additively manufactured Hilbert stator and 0.35 mm laminations below 500 Hz. A torque loss of approximately 20% was observed due to 34% less magnetic material in the Hilbert stator than 0.127 mm laminations, but improved torque density for the stator by 13%. By designing for additive manufacturing, tooth area could be scaled up providing an electrical machine with 3D magnetic flux pathways with acceptable loss behaviour and good magnetic circuit properties, enabling further flexibility to electrical engineers in their pursuit of higher torque and power density.