Experimental Study on Low-Pass Filtering Characteristic of Axial Magnetic Field of No-Insulation and Partial-Insulation HTS Coils Carrying a DC-Biased AC Current

This paper deals with the low-pass filtering characteristic of the axial magnetic field of no-insulation and partial-insulation high temperature superconducting (HTS) coils carrying a dc-biased ac current. Recently, the no-insulation winding technique has been issued as a key technique to enhance the performance of HTS coils in terms of the overall current density, thermal stability, and mechanical integrity. In this paper, to verify the effect of time-varying external distortion on no-insulation HTS coils, an experimental analysis is carried on three HTS coils-insulation, no-insulation, and partial-insulation coils. To simulate the environment in which time-varying external distortion influences the HTS coils, a dc-biased ac current is carried by the HTS coils. The axial magnetic fields of no-insulation, partial insulation, and insulation HTS coils are experimentally tested and analyzed. When the coils carry a dc-biased ac current, the no-insulation and partial-insulation coils have a tendency to attenuate the high-frequency components and to act as a low-pass filter on the axial magnetic field; however, the insulation coil does not attenuate the high-frequency components of the axial magnetic field. The analysis of the experimental results can be useful data for the adoption of no-insulation and partial-insulation windings in superconducting applications.