Impact of Radial Stress on Charge/Discharge Characteristics of a No-Insulation Coil

High temperature superconducting (HTS) no-insulation (NI) coil has excellent thermal and mechanical stability. Regarding the issue of the impact of the inter-turn conductivity distribution on the electromagnetic characteristics of NI coils, this paper selects the D-shape coil, a specially shaped coil structure, to analyze the influence of spatial geometry and winding processes on the inter-turn conductivity. Firstly, the contact resistivity differences due to stress differences within the same turn and between different turns were considered. Then, the charge/discharge process of NI coil is simulated by three-dimensional (3D) finite element method (FEM), and the influence of different turn-to-turn conductivity and uneven magnetic field on electromagnetic characteristics is analyzed. Finally, aiming at the problem that the local loss is too large in the discharge process of the NI coil, an optimization strategy is proposed to reduce the heat loss in the discharge process and improve the thermal stability of the NI coil system.