Characterisation of SiC Varistors at Ambient and Elevated Temperatures for Protection of Superconducting Magnets

High-energy varistors comprised of a silicon carbide (SiC) composite material have been used as an alternative to linear dump resistors for quench protection/energy extraction for superconducting magnets. However, characterisation work is required for accurate simulations, in particular at elevated temperatures. For magnets with a high inductance or large stored energy, energy extraction can take several seconds, during which time the varistor temperature increase can affect the voltage characteristics throughout the discharge. This work presents the variations of the parameters of SiC varistors at ambient and elevated temperature and include their effects to model the energy extraction and discharge, using the scenario of the DTT toroidal field coil quench protection and energy extraction, which will use varistors.