Superconducting Stator Winding for Axial Flux Electrical Machines Applications

Axial flux permanent magnet (AFPM) electrical machines, characterized by disc-shaped rotor and stator structures, offer a high power-to-weight ratio. The replacement of traditional copper stator windings with high-temperature superconducting (HTS) windings has led to the development of lighter, more compact, and higher-performing machines, despite the technological challenges posed by HTS windings. Notably, HTS tapes experience AC power loss when subjected to alternating currents or when interacting with time-varying magnetic fields. Research at the Superconductivity Group in ENEA Frascati, in partnership with ICAS Company, focuses on the electromagnetic characteristics of second-generation (2G) HTS materials, particularly concerning AC loss in HTS coils. This paper presents the experimental results of two HTS coils wound using distinct HTS tape structures and tested within the liquid nitrogen (LN2) temperature range. Building on the geometric data from these coils, the electromagnetic behaviour of superconducting stator winding (SSW) topologies made from them was investigated. Finite element method (FEM) models of two AFPM prototypes, associated with two SSW topologies, were created, analyzed, and compared. By combining experimental data from the HTS coils with simulation results, a preliminary analytical design for AFPM superconducting synchronous prototypes is developed, enabling predictions of their performance across a range of operating conditions and rotor speeds.