Design of Helical Winding for Slotless Partially Superconducting Electric Machines for Aircraft Propulsion

This paper presents a promising winding technique which enables higher power-densities in partially superconducting electrical machines with a slotless stator, e.g., self-supporting windings. Firstly, the formulation for defining the skewing factor of the helical winding is given. Afterwards, the skew angle and how diverse winding configurations can be characterised as a function of this angle is explained, along with different parameters such as the skewing factor, the harmonic content of the magnetomotive force wave in the airgap or the resistance per phase of the winding. The sine-shaped winding, a particular case of helical winding, is shown, with which, thanks to the benefits of the additive manufacturing, a better electromagnetic performance is achieved. Finally, the implementation of the helical winding configuration in a slotless partially superconducting 2 MW high-power and high-voltage electric machine for electric aircraft propulsion is assessed, comparing the machine active part weight and their power density.