Performance Analysis of a Hybrid IGCTs-Mechanical Dc Circuit Breaker for Quench Protection of Superconducting Magnets

In this paper, the conceptual design of a hybrid DC circuit breaker for quench protection (QP) of superconducting magnets in fusion experiments is presented. In this applications currents of the order of tens of kilo-ampere have to be sustained in steady state and interrupted in case of quench with reapplied voltage of several kilo-volt. The scheme proposed for the QP is based on a mechanical switch to handle the current in steady state operation paralleled to a static circuit breaker for the current interruption. IGCTs available on the market have been selected to analyse the obtainable performance; the relationship among the current to be interrupted, the IGCT junction temperature rise, the opening time of the mechanical switch and the number of devices in parallel, as well as between the reapplied voltage and the number of devices in series are reported and discussed.