R&D of superconductors for 70 MW class generators

Abstract

Super-GM has been developing 70MW class superconducting generators (model machines) for 200MW class pilot generator. Three types of NbTi conductors were developed for each of three model machines. Regarding to the high stability type conductors, residual resistance value of 6.5pQ/m was achieved by adopting AI stabilizer.Regarding to the high current density type, IC of 13.81~4 at 5T was realized by reducing void fraction in conductors and maintaining high residual resistivity ratio. For the low AC loss type, high J c and low AC loss (8.1kW/m3) have been succeeded by applying strand insulation and two stage cabling. To confirm superconducting characteristics concerning long-term reliability, IC and AC loss of each conductors were measured under 10,000 times repeated compressive force of 30MPa that is supposed in daily start and stop operation of generator for 30 years. In parallel to the R&D of NbTi conductors, R&D of Nb3Sn conductors were also conducted for enhancement of critical current density and critical magnetic field.