A Fast Calculation Method Based on Full-Boundary Magnetic Field Simulation for Calculating AC Loss in Bi-2223 HTS coils of Double-Stator HTS Machine

In this paper, a fast AC loss calculation method based on full-boundary magnetic field simulation is proposed to address the time-consuming and inaccurate problems faced by the AC loss calculation of Bi-2223 high temperature superconducting (HTS) coils in double-stator HTS machine (DS-HTSM). The term 'fullboundary magnetic field' refers to the magnetic field on the boundary of air domain around the HTS coils in superconducting machines. This method is implemented through two submodels: Model A represents superconducting machine model established by A-V formulation and Model B represents HTS coil model established by H formulation. The nonlinear E-J property and anisotropy of the HTS coil are considered in Model A, which is used to obtain the spatio-temporal magnetic field data on the boundary of the air domain around the HTS coils. Then, a linear interpolation is applied to fit the data to obtain spatio-temporal magnetic field distribution functions on the air domain boundary, i.e., the full-boundary magnetic field. Next, these functions are imposed as time-varying Dirichlet boundary conditions on the corresponding air domain boundary in Model B, thus realizing the full-boundary magnetic field simulation of the superconducting machine. To verify the accuracy and rapidity of the proposed method, the HTS coils are modeled with homogenization, then the AC losses of the HTS coils in DS-HTSM are calculated by using the proposed method and the conventional A-H formulation, respectively. The results indicate that compared with the A-H formulation, the AC loss calculated by the proposed method has only 0.1% error, meanwhile the computation time is greatly reduced from 600 h to 110 h. Finally, taking a 10 kW DS-HTSM prototype in the laboratory as an example, the AC losses of the HTS coil under no-load and rated-load conditions are accurately calculated by using the full-boundary magnetic field simulation method. It can provide a valuable reference for accurately determining the cooling capacity of cryogenic refrigeration system