A Fast Discharge Scheme of Toroidal Field Coils for Fusion Demo Reactors

This paper describes an emergency fast discharge scheme of toroidal field (TF) coils of fusion demo reactors for reduction of induced voltage applied to turn insulations of conductors. TF coils are divided into serially connected segments that are electrically isolated from each other and only the coil segment having a failed coil is rapidly discharged. It was found from a circuit current analysis that this discharge scheme enables to reduce the insulation voltage with a factor of ~0.6 or less and which would contribute to ensure reliability of the turn insulations.