Design of the water-cooling structure for the 100 kA DC mechanical switch in the CRAFT quench protection system

The DC mechanical switch is connected in series with the superconducting magnet in the quench protection system. As the main switch that carries the magnet current for a long time, the temperature of its conductive unit, especially the contact part, inevitably increases significantly during operation. It is necessary to design a water-cooled structure to control the temperature rise. This article introduces the structural design of the conductive unit of the DC mechanical switch for the Comprehensive Research Facility for Fusion Technology quench protection system and uses a combination of theoretical calculation, thermal-electrical coupling simulation, and Fluent simulation to analyze the thermal stability characteristics at a current level of 100 kA. By comparing and studying the temperature rise characteristics of switches under different cooling paths, diameters of water-cooling pipe, and water flow rates, a design basis is provided for determining a 15 mm diameter “∏” shaped cooling water path structure for the mechanical switch. The DC mechanical switch water-cooled structure designed in this article is expected to effectively control the temperature rise level of the contact.