Speaker
Description
To prevent an unintended shutdown of the high-temperature superconducting devices (HTS), the monitoring and diagnosing system to quantitatively estimate the degradation of superconducting properties before the normal transitions occur has been proposed. Only the active power component of the Poynting vector measured around the coil conducting AC transporting current is observed in the system. From these measurements, the distribution of local critical currents in the sample coil is obtained indirectly. It is necessary to quantitatively clarify the relationship between the critical current distributions in the coil and measured values via our system to realize this system. In our previous study, the experimental and analytical results are good agreement on a sample, whose shape is a single pancake coil wound with Bi-2223 multifilamentary tape, under uniform magnetic fields applied to the sample in direction to the parallel to the tapes face. The presentation reports the results of experiments and calculations on a solenoidal coil of 40 turns wound with YBCO tape, conducting ac transport current. Therefore, non-uniform magnetic fields were applied to each turn in the coil. The frequency and the amplitude of the currents were 20-50 Hz and 10–50 A. The tape has a critical current of 104 A in liquid nitrogen under a self-magnetic field. The I-V characteristics of the sample coils were in close agreement with the predictions. The validity of this method is verified by comparing the experimental and calculated results.
