The conceptual design of upgraded 100 kA quench protection system for CRAFT superconducting magnet

Abstract

In the previous scheme of 100 kA Quench Protection System (QPS) in Comprehensive Research Facility for Fusion Technology (CRAFT) project, advanced artificial current zero-crossing technology was used to interrupt the current. Also, the feasibility was verified by both simulation and experiment. However, some significant issues were exposed, including the breaking reliability problems caused by randomness of the post arc and uneven distribution of the recovery voltage in vacuum circuit breaker. In view of the problems, it is of great significance to upgrade the QPS design scheme in CRAFT project. In this paper, a new 100 kA/10 kV QPS topology is proposed, and the working principle of the new topology is introduced firstly. Then the complete commutation process is divided into three stages to carry out a more effective analysis of the theoretical feasibility of the new topology. Furthermore, a series of simulations including the electrical performance of each device in commutation process and temperature prediction simulation of the used semiconductors are carried out. Finally, the optimized design scheme is obtained to meet the technical requirement of CRAFT project. Compared with the previous QPS scheme, the new scheme has much higher action speed and lower cost.