Experience in HTS-2 Annular Field Coils for a High-Power Synchronous Generator

The Institute for High Energy Physics of National Research Centre “Kurchatov Institute” has developed a technology for manufacturing annular coils from a second-generation high-temperature superconductor (HTS-2 tape). Together with the Moscow Aviation Institute, two field coils for a synchronous generator model were designed and manufactured using HTS-2 tape in in-house cryostats. A method is also developed for applying electrical insulation to the HTS-2 tape, consisting of polyimide film layers with a total thickness of 26 μm. This insulation provides sufficient electrical strength at a voltage of 2500 V and a pressure of up to 5 kg/cm2. During the intermediate manufacturing stage, after coil winding and applying the bandage, the coil quality is monitored by measuring the critical coil current while immersed in a liquid nitrogen bath. Finally, the coils, housed in their cryostats, are cooled with liquid nitrogen in a pumping mode. When cooling the coils to operating temperature, the pressure drop of the cryogen flow is 0.02 MPa, with a cooling time of approximately 1 h. The limiting current value with a stable coil operation is determined. This current is 116 and 126 A for the first and second coils, respectively, which exceeds the calculated operating current when using these coils in the generator model. An experimental model of a synchronous generator with these HTS-2 coils used as axial field coils is manufactured and tested. The generator’s no-load characteristics, as well as its load and control characteristics, are measured during testing. The test results correspond to the calculated ones.