Anodized Aluminum Foil Winding Axial Flux Machine for Direct-Drive Robotic Applications

Abstract

There is a need for higher specific torque electric actuators in novel direct-drive robotic applications. Since the specific torque is inherently limited by material properties, designers have to look at novel materials to push the specific torque limit further. In this article, anodised aluminium foil is considered as an alternative to enamelled copper wire in a yokeless and segmented armature axial flux machine. This machine topology has a high specific torque and is particularly suited for an anodised aluminium foil winding. The DC resistance, thermal properties and eventually the specific torque of a prototype test case machine are compared for both winding materials. A 3D thermal finite element model is used to analyse the influence of the thermal interface between winding body and housing, and the influence of the cooling performance on the specific torque. To conclude, anodised aluminium foil winding offers a higher specific torque in direct-drive yokeless and segmented armature axial flux actuators where the winding body thermal resistance is dominant in the thermal path from heat source to heat sink. It is experimentally shown that for the prototype machine, the torque per kg active stator mass increases 13% through the use of anodised aluminium foil.

State-of-the-Art Lightweight Implementation Methods in Electrical Machines

“…(1) a lower mass density, accounting for only 30% of that of copper; (2) a reduced cost, i.e., approximately 10% the price per unit volume compared to copper; (3) a higher heat capacity, roughly double that of copper per unit mass; and (4) enhanced recyclability. Consequently, aluminum is being increasingly utilized as a substitute for conventional copper materials in specific scenarios, with the expectation of achieving lightweight configurations and cost-effectiveness [32][33][34].…”

Anodised Aluminium Foil Winding Axial Flux Machine for (Quasi-)Direct-Drive Robotic Applications: Preliminary Design and Manufacturing

“…Additionally, the good thermal conductivity in the plane of the foil opens opportunities to cool the windings effectively via the airgap both in radial and axial flux machines. A thorough thermal comparison of an anodised aluminium foil winding and enamelled round copper wire winding in a YASA AFPMSM can be found in [62].…”