Development of a double stranded cable superconductor for 70 MW class superconducting generator with quick response type

We have been developing a 70 MW class model generator aiming at a 200 MW class pilot machine. The superconductor developed for field winding of a generator has a configuration of double stranded cable, composed of NbTi, Cu and CuNi. The strand is insulated by formvar and seven strands make a 1st stage cable. Eleven 1st stage cables make a 2nd stage cable, and are compacted to rectangular cross section. The inter-strand resistance and AC loss of superconductors are measured under the conditions of compressive mechanical force up to 19.6 MPa to simulate the centrifugal force of the generator rotor winding. From those results, we consider the relation between inter-strand resistance and inter-strand coupling loss. Based on those results, we are designing the superconductors for the 70 MW class model generator with quick response, taking the insulation of the strand into account.<>