A Fast AC Field Controlled Impedance in HTS Coated Conductors: Response Speed and Electric Field Value
Direct current carrying Type II superconductors present a dc electric field under external perpendicular ac magnetic field. This effect can also be considered as an equivalent dynamic resistance. The minimum field magnitude required to generate the dynamic resistance is less than the fully penetration field of the superconductor, which is much less than its upper critical field. Thus, the superconductor can remain superconducting, leading to fast recovery times and meaning that it is feasible to use dynamic resistance to add a controlled impedance into the system. In this study, we built a demonstrator using a section of YBCO coated conductor controlled by an external ac field of a wide frequency range. We tested the electric field value and response time of the system. The work may be indicative for designing impedances for flux pumps or superconducting magnetic energy storage systems.