Intensive R and D efforts for superconducting generators are being made in Japan with the support of MITI: A 6MVA superconducting generator was developed in 1977 and now a 30MVA superconducting synchronous condenser are being developed as a joint study of Mitsubishi Electric Corp. and Fuji Electric Co. In US and USSR, 20MVA superconducting generators are being fabricated and the developments of 300MVA machines are scheduled. In France a superconducting model rotor of a practical diameter (-1m) has been developed. This paper describes the purpose of the development and the state-of-art of superconducting generators
A pulsed magnet with stored energy of 363kJ has been developed. The central field is 3T at 2100A. The conductor is a braid which is composed of 120 strands with a mixed matrix (Cu and CuNi) and is not solder-filled and thus not mechanically rigid. The magnet consists of 25 double pancake coils and the size is 40cm, 50cm and 59.2cm in i.d., o.d. and axial length, respectively. Turn to turn insulation is provided by a 0.5mm thick and 6mm wide semi-cured epoxy glass-cloth tape, which is wound about the braid, for the 13 double pancake coils, and by a cured epoxy glass-cloth tape for the other coils. The semi-cured tape is heat treated after winding. The magnet was charged at a sweep rate of about 0.05T/sec up to 2250A without quenching where the stored energy was about 418kJ. In pulse operations, it was charged to 3T in about 5 seconds and discharged to zero in about 1.65 seconds without quenching. At a faster charging rate, however, it was quenched. During the charge, major conductor motion was observed in parts of the double pancake coils wound with the braid wrapped with the cured tape, and hence the quenching will be attributed to the conductor motion. We are now rewinding those double pancake coils by using the braid wrapped with semi-cured epoxy glass-cloth tape.
A number of superconducting coils wound with multifilamentary Nb3Sn or V3Ga wires has been developed. The large majority of those had an inner diameter of about 50mm and a central magnetic field over 10T, and some of them has already been put on the market. But as far as high field coils with an inner diameter in excess of 100mm are concerned, there exist only a few examples. The former is generally a solenoidal close packed coil manufactured by the wind-and-react method, and the latter is mainly a pancake coil constructed from prereacted conductors. Superconducting coils wound with multifilamentary compound wires will be developed further towards the aim of achievements of higher fields in large volume. It is therefore important to analyze the state-of-art and clarify the problems.