AC-induced DC voltage in HTS coil

The interplay between AC and DC currents in a High-T-c Superconducting (HTS) coil, made of multifilamentary silver-sheathed Bi-2223 tape, was investigated. We observed that the application of a small sinusoidal current in the frequency range of 50-500 Hz into the coil, while it is already carrying a DC current in the range of 16-22.5 A, caused an increase in the coil DC voltage. The DC voltage increment due to the AC signal is found to increase linearly with frequency and quadratically with amplitude. The DC voltage increment increases as the coil current grows towards its critical value of 22.2 A. This result may be important in some power applications such as fault current limiters (FCL) and superconducting magnet energy storage (SMES) based on HTS coils. (C) 1998 Elsevier Science B.V. All rights reserved.