AbstractNext fusion research experiments plan to use many superconducting magnets. When a quench phenomenon is observed, the current should be interrupted to protect the magnet. Therefore, a dc circuit breaker is necessary. There are four technical situations to be considered for the dc circuit breaker system; (1) high rated current, (2) smaller size breaker, (3) high reliability and (4) no surge voltage during the interruption. The size of the breaker is limited by the arc current density of the contacts, and the low current density is better in the circuit breakers. A high rated current also needs the large contacts of the breaker. Here, we introduce a new type of dc circuit breaker system which does not generate an arc plasma between the contacts, equip the high rated current disconnecting switch and a fuse for the failure of the interruption, and use the conventional ac breaker. The switch size of the breaker is almost one hundred times smaller than that of the previous switch.
The new technological solution for the JT-60SA quench protection circuits