R&D of superconductors for 70 MW class generators

Super-GM has been developing 70 MW class superconducting generators (model machines) for a 200 MW class pilot generator. Three types of NbTi conductors were developed for each of three model machines. Regarding the high stability type conductors, residual resistance value of 6.5 /spl mu//spl Omega//m was achieved by adopting an Al stabilizer. Regarding the high current density type, Ic of 13.8 kA at 5 T was realized by reducing void fraction in conductors and maintaining high residual resistivity ratio. For the low AC loss type, high Jc and low AC loss (8.1 kW/m/sup 3/) 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 conductor were measured under 10000 times repeated compressive force of 30 MPa that is supposed in daily start and stop operation of a generator for 30 years. In parallel to the R and D of NbTi conductors, R and D of Nb/sub 3/Sn conductors were also conducted for enhancement of critical current density and critical magnetic field.