Dynamic Response of No-Insulation and Partial-Insulation Coils for HTS Wind Power Generator

In this paper, we present results, experimental and numerical, of the electromagnetic interaction forces between pairs of racetrack coils under time-varying conditions. Three turn-to-turn insulation designs were applied to wind three racetrack coils with GdBCO coated conductor: 1) no insulation (NI); 2) partial insulation (PI) of a polyimide layer every eight turns; and 3) insulation (INS) of a polyimide layer between each, i.e., NI, PI, and INS racetracks. Two racetrack pairs, namely, NI-INS and PI-INS, were tested for their interaction forces, measured with load cell under current-ramping conditions in a bath of liquid nitrogen at 77 K. Good experimental and simulation results validate our equivalent circuit model to compute interaction forces of PI-INS racetrack pair. Overcurrent test of NI and PI coils, where each racetrack coil was charged above critical current (I_c), was also performed to compare coil stability. This result implies that, although the PI winding technique improves the dynamic response, stability will be somewhat compromised.