Heater-induced quenches in a model field winding for the 70 MW class superconducting generator

Quench studies were performed using a model field winding for the 70-MW-class superconducting generator to investigate the minimum quench energy, the longitudinal and turn-to-turn quench propagation velocities, and the temperature rise of the hot spot. The model field winding is a racetrack coil with 88 turns which was wound in a slot of the support structure and compressed by a flange. The 15-strand cable was selected as a conductor to reduce the AC losses that will be generated at the system fault. A ceramic chip heater was glued on the surface of the racetrack coil to initiate quenches. Two pairs of voltage taps were used to determine the quench propagation velocities. A Cu+0.15% Fe-Chromel thermocouple was soldered near the ceramic chip heater to measure the hot spot temperature. The data obtained in these experiments will be used to design the quench protection system for the field windings of the 70-MW-class superconducting generator