Real-Time Electromagnetic Simulations of Large-Scale REBCO Solenoid Coils by Combination Model

In this article, we employ the combination model, where thin-strip, homogeneous, and multiscale methods are simultaneously employed by using T-A formulation, to successfully implement the real-time electromagnetic simulations of large-scale rare-Earth-barium-copper-oxide (REBCO) solenoid magnets. First, we extend the combination model from 2D planar geometry to 2D axisymmetric geometry, where enhancements on the data transferring are made to simplify the modeling process. The accuracy and efficiency of the combination model are validated by simulating a medium-size REBCO coil operating in ac conditions, as well as another two T-A models: the full and the homogeneous models. Comparison results show that distributions of hysteresis losses, current density, and magnetic field from the combination model and the T-A full model are highly consistent. Meanwhile, the combination model is the most time-saving one, which makes it suitable for simulating larger-size magnets. Then, the combination model is used to study the effects of screening current on the magnetic-field homogeneity and drift in a 7-T REBCO-based nuclear magnetic resonance (NMR) magnet whose total number of turns is up to several thousand. Transport currents with various ramping and the same plateau time are imposed in the magnets, and different change trends of the magnetic-field homogeneity are presented. Noteworthy, it only takes 12.4 min to finish the 70-h charging of the NMR magnet. The study indicates that the combination model has the potential to be employed in the design of REBCO-based magnets considering screening current and to be a basic model for multiphysics coupling because of its high efficiency.