Calculation method study of HTS coils' critical current

A method to calculate second-generation (2G) high temperature superconducting (HTS) coils' critical current is presented. Critical current and n value of HTS tapes measured under different magnet field are used for the calculation of the coil. The distribution of HTS coils' magnetic field intensity, current density, and electric field intensity is calculated with COMSOL 2-D based on H formulation. A partial differential equation (PDE) model and the magnetic field formulation (mfh) model of HTS tape are constructed. The modeling method and key points are also introduced and discussed. AC loss of the HTS tape is calculated with the above-mentioned two models, respectively. The calculation results of the two modeling approaches are coincident. The cross sections of the straight segment and bending segment of a HTS racetrack double-pancake coil are modeled, respectively, with a 2-D and 2-D-axisymmetric model in COMSOL, and the critical current is calculated. E-I properties of each turn of the coil and the critical current are calculated. HTS coils with seven pairs of voltage lead are wound. Voltages at different parts of the coils and the critical current are measured. The measurement results of the magnetic field, electric field, and critical current agree with the calculation results. The method presented in this paper can also be referred to when designing an HTS machine with HTS tapes or coils.