A Numerical Method for Determining Critical Current of ReBCO Coils: Modelling Details, Validation, and Comparison with T-A-Formulation

High temperature superconductor (HTS) coils have been applied in high field magnet applications, such as nuclear magnetic resonance (NMR) and maglev trains. The accurate calculation on the critical current of HTS coils is key for the magnet design and optimization. An effective way to calculate the critical current of HTS coils is the quasi-critical state model based on T-A formulation and E-J power law, which works well in 2D models, but suffers from hard convergence and huge computations in 3D models. A simple way of critical current calculation is to use a magnetic field model based on uniform current assumption. This improved model avoids solving highly-nonlinear equations and the calculation cost is greatly reduced, thus can be a more practical solution for the critical current estimation of HTS coils with complex geometry. This paper studies and compares critical current of circular and racetrack HTS coils, the critical current of each coil is calculated by T-A model and the improved uniform current model. Results from the uniform current model shows consistency with T-A model with a discrepancy lower than 5% for most cases. This paper aims to provide a simple and fast modelling method for the critical current estimation with enough accuracy for HTS coils.