Development of NbTi Superconducting Strands and Cables for the Field Winding of a 200-MW-Class High-Energy-Density Superconducting Generator

摘要

The NbTi superconducting strands and cables for the field winding of the 200-MW-class high-energy-density-type superconducting generator are developed. They are composed of Cu/Cu-10wt%Ni/Nb-46.5wt%Ti superconducting strands and the 10-kA (at 5 T)-class 9-strand compacted cables. The diameter of strands is 1.33 mm, and the 9-strand compacted cables are 2.4 mm thick and 6.0 mm wide. In order to produce high-current-density NbTi strands, we made strands under controlled aging heat treatments, the total and final strains, and the strains between heat treatments, by using large-scale extruder. Moreover, in order to produce high-stability and low-AC-loss NbTi strands and cables, the matrix ratio of strands and the cross sections of strands are optimized. The current density of NbTi filaments for the four-time-aging manufactured 1.33-mm-diameter strands was J{sub}C = 3150 A/mm{sup}2 at 5 T, 1150 A/mm{sup}2 at 8 T. The critical current of the 9-strand compacted cable is 10.7 kA at 5 T. The AC losses of the final compacted cables are less than 100 kW/m{sup}3 at 5 T, 5 T/s, that is, decreased to less than half of the target of the AC loss value (< 200 kW/m{sup}3 at 5 T, 5 T/s). Compared with the strand (Cu ratio 1.77), the minimum quench energy (MQE) of the strand (Cu ratio > 2) increased about 40% at the operation mode current of the superconducting generator.