Concept design of 100 kA hybrid DC breaker on China fusion engineering test reactor

Abstract China Fusion Engineering Test Reactor (CFETR) is the next device for the Chinese magnetic confinement fusion program, which is now under conceptual design phase. This paper describes the concept design of the high current hybrid breaker for the quench protection of superconducting magnets. The rated currents and maximum reapplied interruption voltages for breaker are 100 kA and 20 kV. The concept solution design of DC breaker is presented, which is mainly composed of a mechanical main switch with three levels contacts for conducting the continuous current, and a solid-state switch in parallel for current transferring. The design principles of each part and the preliminary results are given respectively. Finally, two test platforms were built to verify the calculation and design. Compared with the traditional oscillation zero-point DC breaker, the hybrid breaker topology can improve the dielectric strength recovery speed of mechanical switch and reduce the whole operation time. It is more suitable for fast current interruption at heavy DC current level