Design and Test of Magnetic Shielding for Vacuum Circuit Breaker of CRAFT Quench Protection System

The quench protection system is an important part of the Comprehensive Research Facility for Fusion Technology (CRAFT) superconducting magnet high-power power supply support platform. It can quickly complete the breaking and transfer of 100-kA magnet current when a quench event occurs in a superconducting magnet. This article introduces the dc switch circuit topology of the CRAFT quench protection system, mainly for the vacuum circuit breaker of its transfer branch, puts forward the design of a series double-fracture structure, and establishes a simulation model to calculate and analyze the longitudinal magnetic field characteristics of vacuum arc in the fracture gap of vacuum circuit breaker under this structure, and comparative calculations were made on materials and thickness, providing a basis for the design of the magnetic shielding cover. In addition, by building the dc breaking experimental platform and conducting the breaking current experiment of the vacuum circuit breaker, the effectiveness of the magnetic shielding design is further verified, and the breaking reliability of the dc vacuum circuit breaker of the CRAFT quench protection system is improved.