Study of a low-frequency wireless charging system crossing the metal Dewar wall of a high-temperature superconducting magnet

Abstract Using a wireless charging method to charge high-temperature superconducting (HTS) magnets is a way to solve the existing problem of high leakage heat introduced by charging through current leads. However, the available studies on charging HTS magnets using wireless charging methods rarely involve the role of a Dewar in the charging process. Nowadays, most HTS magnets use a metal Dewar because of the high requirements of the Dewar for gas tightness and mechanical strength. How to charge the HTS magnets wirelessly through the metal walls of the Dewar is an issue that needs to be addressed. In response to the above concerns, taking into account the role of the metal Dewar, a low-frequency wireless charging system with an isolation transformer as the core is proposed in this paper, where the primary coil of the transformer is a copper coil, installed on the outside of the Dewar. The secondary coil is a superconducting coil, installed on the inside of the Dewar. A theoretical model of the proposed wireless charging system is developed, and the prototype is fabricated based on the theoretical model. Both numerical and experimental methods were used to study the operational characteristics of the prototype, and the experimental results proved the validity of the theoretical model and the numerical model in this paper. Experimental results show that the proposed wireless charging system can charge an 8.5 mH HTS magnet with a current of 48.58 A over a 6 cm transmission distance, where the 6 cm gap includes a 1.6 mm thick metal wall. The results in this paper can provide new ideas for research work on charging HTS magnets wirelessly through a metal Dewar.