AC loss measurement of HTS coils at around 20K for HTS machines

Electric and hybrid aircraft are thought to be one of the most promising technologies to realize net zero aviation. Superconducting machines with potential high power and low weight are agreed to meet the future demands for aircraft propulsion. In order to enable the design of future cryogenic systems and achieve AC loss reduction for fully HTS machines, it is necessary to generate data on AC losses at different operating temperatures. Therefore, the use of gaseous helium as a cryogen can offer the required operational flexibility for such HTS power applications. Our previous study has reported the manufacturing of multi-filament HTS coils and confirmed substantial AC loss reduction. This paper, as a follow-on study, will focus on quantifying further AC loss reduction of different HTS windings in a rotational machine environment at temperatures lower than 77 K. Therefore, in this work, a newly designed fully HTS machine using the cryogenic helium circulation system as the cooling method will be introduced, which is able to provide a machine environment to measure the AC losses of HTS stator windings at temperatures around 20K. Then Finite Element Modelling will be applied to validate the experimental results, as a future guidance for improving the system design. As a result, the cooling methodology through such a cryogenic gas circulation system is expected to further improve the performance and power density of the fully HTS machines, thus maximizing the overall machine efficiency.