Study on the commutation mechanism of quench protection systems for large-scale superconducting magnet based on arc characteristics

Abstract Large-scale superconducting magnets serve as critical components in magnetic confinement nuclear fusion devices, whose operational integrity critically depends on highly efficient quench protection systems (QPS). The QPS facilitates the transfer of massive energy stored in superconducting magnets to fast discharge resistor via the interruption operation of high-capacity circuit breakers. The electric arc generated during current interruption profoundly influences the transient characteristics of current transfer and overall system safety. Based on a high-power supply platform, this study presents, for the first time, experimental measurements of the spatiotemporal evolution characteristics of arc voltage during the interruption process of a direct current breaker at the 10 kA level under various steady-state current conditions. By integrating theoretical analysis with experimental methodologies, a refined mathematical model was developed to conduct an in-depth investigation into the impact of the nonlinear time-varying characteristics of the arc on current transfer time during switching operations and contact erosion. This research provides significant insights into the physical processes governing current transfer in QPS, as well as the dynamic characteristics of vacuum arcs and their influencing factors. Furthermore, it offers valuable guidance for the design, development, and performance optimization of high-capacity quench protection switches intended for future superconducting magnet systems.