Developing Test Apparatus and Measurements of AC Loss of High Temperature Superconductors
Abstract
To reduce the weight of electrical power conductors for use on airborne platforms, high-temperature superconductor coated wires using YBa2Cu307-x(YBCO) show promise. The main obstacle to their implementation is the AC loss at operating frequencies in the 230-400 Hz range characteristic of the airborne electrical power systems and generators. This project's objectives were threefold. First, a calorimeter measuring system for AC loss was developed using custom construction of nonmagnetic/nonmetallic liquid nitrogen containers to measure evaporated nitrogen caused by power dissipation and tested using a special YBCO pancake coil; this was found to be sufficient for measurements after initial experiments determined some instability without external heating. Second, AC losses in the coils made out of YBCO superconducting wires were studied, confirming the simulation method used to calculate and predict AC loss and hysteretic effects of pancake coils and providing information on the coupling and hysteretic currents in the superconductor. Third, distribution of magnetization currents in samples of conductors was studied by producing, using laser ablation, multifilament superconducting samples with various filament widths, with and without superconducting bridges between filaments. The bridges increase the reliability of the wires by allowing the electric current to circumvent a defect in a given filament without rendering the whole length of the filament inoperative. Different methods of post-ablation treatment, such as oxygen annealing were tested in order to determine their effect on AC loss reduction. Results showed that the AC loss in multifilament superconducting wires can be very effectively reduced in proportion of the number of filaments. The oxygen annealing eliminates the residual coupling losses by converting the electrically conducting metal in the grooves segregating the superconducting filaments into insulating metal oxides. The strategically placed supercon
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 2012
- Accession Number
- ADA570228
Entities
People
- Milan Polak
- Pavol Kovac
- Timothy J. Haugan
Organizations
- Slovak Academy of Sciences