Electromagnetic-thermal finite element model coupled to reduced electrical circuit for simulating inductive HTS coils in overcurrent regimes

To improve the understanding of the behaviour of High Temperature Superconducting (HTS) devices in electrical systems, it is relevant to couple Finite Element (FE) Models (FEM) and Electrical Circuits (EC). This coupling should include enough physics to look justly at the impact of the devices on the electrical system. Since some devices require the full or partial transition of the superconductor to its normal-resistive state, such as fault-current limiters, for instance, their modelling must address the dynamic change that the superconductor experiences moving both ways between its superconducting state and its normal-resistive state. To tackle this challenge, a multiphysics FEM coupled to an EC has been built targeting overcurrent operations of 2G HTS coils, used in such devices. Here, the basis of the approach is the electromotive force to compute the magnetic induction in the coil. The FEM is composed of two coupled submodels, an Electromagnetic one (EFEM) implementing the T-A formulation and a Thermal one (TFEM). The resulting TEFEM is coupled to an Electrical Circuit Model (ECM) in the same FE solver yielding the TEFEM − ECM. To further improve the computation time, a reduction method is employed to skim the ECM, without sacrificing accuracy. The simulation results for the most reduced version of the model are compared with experimental data obtained in liquid nitrogen at 77 K for a current pulse discharge system connected to a 2G HTS coil, showing good agreement.