Impedance variation of a flux-lock type SFCL dependent on winding direction between coil 1 and coil 2

The flux-lock type superconducting fault current limiter (SFCL) uses the magnetic coupling between two coils connected in parallel with each other. This SFCL has the merit that both the resistance of high-T_C superconducting (HTSC) element and the limiting current capacity can be simultaneously increased through the application of magnetic field into HTSC element. However, unlike other types SFCLs, the different fault current limiting characteristics can appear according to the winding direction between the two coils. In this paper, the relation of the impedance of the flux-lock type SFCL with the resistance of HTSC element was derived from its equivalent circuit using the current and the voltage relationship between the two coils. The limiting impedances of the flux-lock type SFCL due to the winding direction through the discrete fourier transform (DFT) analysis for the voltage and the current data obtained from the fault current limiting experiments were extracted and analyzed from the point of view of the limited line current and the resistance of HTSC element.