A 170-kA DC circuit breaker for the quench protection of the central solenoid coil of the ITER tokamak

High current and high voltage DC circuit breakers have already been used in the field of fusion technology, in the Joint European Torus (JET) (P. Doko pulos and K. Kriechbaum, DC Circuit Breaker Arrangement 73 kA, 24 kV for th e Joint European Torus, Elektrotechnische Zeitschrift A, 1976; P.L. Mondino , The JET ohmic heating circuit, 9th Symposium on Engineering Problems of F usion Research, Chicago, US, Vol. 1, October 1981, pp. 386-389) and JT60 (R . Shimada et al., JT 60 power supplies, Fus. Eng. Des. 5 (1987) 47-68; R. S himada et al., Development of high current DC circuit breaker for large Tok amak device, Fusion Technol. 1 (1978) 401-406) Tokamaks, with pulsed curren ts up to 90 kA or more, but were not able to simultaneously carry steady st ate currents of 60 kA and to interrupt current under high voltage. Therefor e, R&D on high current (60 kA) and high voltage (20 kV) switches, especiall y on DC circuit breakers, has been undertaken in order to ensure the protec tion of the superconducting coils of the ITER Tokamak (Y. Shimomura et al., ITER Overview, 17th IAEA Fusion Energy Conference, Yokohama, Japan, Octobe r 1998; M. Huguet, The Integrated Design of the ITER Magnets and Their Auxi liary Systems, 17th IAEA Fusion Energy Conference, Yokohama, Japan, October 1998) in case of a quench Ci. Shimomura et al., ITER Overview, 17th IAEA F usion Energy Conference, Yokohama, Japan, October 1998). For this purpose, the coil magnetic energy (in the range of several GJ) is discharged in a la rge resistor connected in parallel with the DC circuit breaker, Most of the coil circuits operate at 60 kA maximum DC current. Nevertheless, the Centr al Solenoid (CS) coil (Y. Shimomura et al., ITER Overview, 17th IAEA Fusion Energy Conference, Yokohama, Japan, October 1998) of the ITER Tokamak was designed, till the middle of 1998, to be operated at 168 kA. The assessment of such a circuit breaker concept, using parallel operation of 60 kA rated mechanical switches, will be developed in this paper. This theoretical ana lysis assumes the use of pure mechanical switches connected in parallel wit hout any use of semi-conductor devices. (C) 2001 Elsevier Science B.V. All rights reserved.