Evaluation of a solid nitrogen impregnated MgB₂ racetrack coil

To develop powerful wind turbine generators using superconducting technology, high-performance superconducting racetrack coils are essential. Herein, we report an evaluation of a multifilamentary magnesium diboride (MgB₂) conductor-based racetrack coil cooled and impregnated simultaneously by solid nitrogen (SN₂). The coil was wound on a copper former with 13 mm winding width, an inner diameter of 124 mm at the curvature, and 130 mm length of the straight section. An in situ processed S-glass-insulated 36-filament MgB₂ wire was wound on the former in two layers with 19.5 turns, and heat treated via the wind and react method without any epoxy resin. The coil was evaluated for critical temperature and transport critical current in the SN₂ environment at different temperatures up to 31.3 K in self-field. The coil was able to carry 200 A transport current at 28.8 K in self-field. During coil charging and operation, SN₂ effectively acted as an impregnation material. The test results demonstrate the viability to use MgB₂ racetrack coil potentially with SN₂ impregnation in advanced rotating machine applications.