Study on No-Insulation HTS Pancake Coils With Iron Core for Superconducting DC Induction Heaters

This paper focuses on no-insulation (NI) HTS pancake coils with iron core for superconducting dc induction heaters. A superconducting coil without turn-to-turn insulation and its conventional counterpart with insulation are wound with YBCO-coated tapes. An iron core is built for a laboratory-scale dc induction heater. The electromagnetic characteristics of the two coils with the iron core are studied focusing on the charging and sudden-discharging processes at 77 K. Three variables are measured, i.e., current, terminal voltage, and magnetic field induced. The results show that NI coil with the iron core incurs a significant delay in the charging and discharging process due to the influence of the iron core. A terminal voltage pulse is observed at the beginning of the sudden-discharging process, which is more than five times of its normal value. A circuit-field coupled method is proposed to analyze the electromagnetic characteristics of the NI coil with an iron core. The results from experiment and simulation exhibits good agreement. The research shows that it is possible to use the NI technique to build a HTS iron core magnet for a dc induction heater, which can simplify the quench protection system.