In many high-temperature superconducting (HTS) applications, such as high-field magnets, rotating machines, and linear actuators, no-insulation (NI) coils are an appealing alternative to insulated (INS) coils. The advantages of NI coils, including higher current density, better mechanical integrity, thermal stability, and self-protecting properties, make them a more attractive technological choice compared to INS coils [1]. In the applications mentioned, coils are exposed to time-varying magnetic fields that induce magnetization loss. The loss characteristics may differ between NI and INS coils, and this must be addressed before replacing INS coils. This loss can vary depending on the applied field angle and frequency, creating a parasitic heat load that significantly impacts the design of cryogenic systems. Therefore, it is essential to investigate the behavior of this loss under different conditions to ensure successful system design.
In this work, we investigate magnetization loss in NI and INS double-pancake and double-racetrack coils both experimentally and numerically. Experiments were conducted at 77 K under AC external magnetic fields up to 100 mT, considering various field angles (0o ̶ 90o) and frequencies (72-146 Hz) in NI and INS coils of the same dimensions, wound with SuperPower superconductors. Numerical results from a 3D model of the NI and INS coils, implemented in COMSOL Multiphysics, are then compared with the measured loss values. Additionally, we analyze current density distributions and magnetic field penetration profiles to better understand the magnetization loss behaviors in NI and INS coils.
[1] S. Hahn, K. Radcliff, K. Kim, S. Kim, X. Hu, K. Kim, D. V. Abraimov and J. Jaroszynski, “Defect-irrelevant behavior of a no-insulation pancake coil wound with REBCO tapes containing multiple defects,” Supercond. Sci. Technol., vol. 29, Art. no. 105017, September 2016.
This work was in part supported by the New Zealand Ministry of Business, Innovation and Employment under the Advanced Energy Technology Platform program “High power electric motors for large scale transport” contract number RTVU2004 and in part supported by the Air Force Office of Scientific Research under award number FA2386-22-1-4054.