AC Loss and Voltage Signal in a Pancake Coil Made of Coated Conductor With Ferromagnetic Substrate
The voltage signal and the AC loss in a pancake coil made of a coated conductor tape with magnetic substrate is measured. The experimental data have been analyzed with the help of numerical calculations. It is found that while for a single tape the AC loss is dominated by the substrate, for the coil it is dominated by the superconducting layer. Moreover, the substrate increases the AC loss generated in the superconducting material, making it similar to a slab. A compensation method for the voltage signal is also described, thanks to which the contribution from the substrate and the superconducting layer can be distinguished.
Influence of DC Magnetic Field on AC Loss of YBCO Coated Conductor with Ferromagnetic Substrate
Most of YBCO tape conductors are prepared on a ferromagnetic substrate. The ferromagnetic material is then exposed to the self magnetic field of the superconductor and also to external magnetic field. In AC magnetic field hysteretic and eddy current losses are generated in the substrate. In this work the AC transport loss of an YBCO coated conductor on a ferromagnetic substrate was measured using electromagnetic method. There are two contributions to total loss — a loss in the superconductor and a loss in the substrate. To suppress the hysteretic loss in the substrate, it is possible to saturate it using DC magnetic field. In this regime significant decrease in total loss was observed.
Electrical behavior of Bi-2223/Ag tapes under applied alternating over-currents
As a study for the protection of HTS power machines operated under AC conditions, the electrical behavior of Bi-2223/Ag tapes with applied alternating over-currents was investigated. Using the HTS tape of 57 A I/sub c/ and 106 K T/sub c/, we measured the V-I curves for the over-critical current region from 150 A/sub p/ to 507 A/sub p/. From the experimental results, 3 matters were investigated. Firstly, using the resistance increase data obtained from the curves, quench development was analyzed as a function of the amplitude and duration of the applied currents. Secondly, to understand these phenomena in detail, we investigated the current distribution between the superconductor and the metal sheath in Bi-2223/Ag tape, applying the equivalent equations and data of V-I curves. Finally, we confirmed the relationship between the resistance and temperature generated by the over-critical current experimentally. As a result, we could find the optimal operating condition considering the protection of the HTS tape against the alternating over-current.