Partial-Insulation HTS Magnet for Reduction of Quench-Induced Peak Currents.

ABSTRACT

The No-insulation-like (NI) coil's turn-to-turn current paths prevent local heating by forcing the current to bypass into nearby turns when a hot spot appears in a coil. However, the changing direction of the current by bypassing will change the magnetic flux, which generates unwanted induced currents in the adjacent coils in a multiply-stacked HTS magnet. This induced current can temporarily exceed the designed maximum currents in the NI coils, damaging the magnet. A partial-insulation (PI) coil, in which a single or multiple insulated, with a polyimide-like material or a thin ceramic film, is inserted between windings to hinder the current paths, can reduce the peak induced currents in the NI HTS coil's current paths. In this paper, we present the results of a simulation study on the peak-induced current upon a quench of the PI HTS magnet with a double pancake. The study shows that the peak-induced current varies with the number of insulated turns. We also discuss the induced current turn-by-turn simulation. According to the simulation result, the PI effectively reduces overall induced current, especially insulation applied every two turns.