Investigation of HTS racetrack coil without turn-to-turn insulation for superconducting rotating machines

This paper reports a study of two HTS racetrack coils wound with GdBCO coated conductors, one without turn-to-turn insulation and the other with Nomex insulation. The coils were characterized by charge-discharge, over-current, and sudden discharge tests. Thermal and electrical characteristics of the GdBCO racetrack coil without insulation outperformed the insulated one. The test results confirmed that although the coil without insulation has a slow charging/discharging time constant, the no-insulation winding technique may enable a compact and protection-free racetrack-typed coil with enhanced mechanical integrity as well as better thermal and electrical stabilities.