Inversion of Equivalent Contact Resistivities of Parallel-Wound Metal-Insulation HTS Coil Based on Experimental Data and Multilevel Simulation

Equivalent contact resistivity is a key parameter that affects the dynamic process and overcurrent characteristic of the non-insulation (NI) HTS coil. Adding stainless-steel material between turns of a parallel-wound NI coil results in the formation of various types of internal contact interfaces. Therefore, describing the shunt behavior of the coil, i.e., the parallel-wound metal-insulation (PWMI) coil, requires more than one equivalent contact resistivity, which makes it difficult to determine their specific values only through coil inductance and time constant. To handle this problem, we propose a method for acquiring distinct equivalent contact resistivities of the PWMI coil. In this method, the equivalent contact resistivities are inverted based on the measured coil voltage or magnetic field. The bridge to connect the experimental data and equivalent contact resistivities is the streamlined field-circuit coupling model based on T-A formulation, which can reflect the complex electromagnetic topology and the distribution of equivalent contact resistivities of the PWMI coil. After obtaining the measurement results, the least squares method is used to optimize the equivalent contact resistivities until the simulation curve is sufficiently consistent with the experimental curve. In order to improve the efficiency of the optimization, we construct the lumped circuit model of the PWMI coil. Before the optimization process begins, the initial values of equivalent contact resistivities can be obtained based on this model, which can reduce the search scope of the optimization. The results of multi-process testing indicate that using the equivalent contact resistivities obtained by the proposed method can effectively predict the transient behavior of the coil.