Comparison of 2D simulation models to estimate the critical current of a coated superconducting coil

Abstract

Superconductors have been being applied to a variety of large-scale power\napplications, including magnets, electric machines, and fault current limiters,\nbecause they can enable a compact, lightweight and high efficiency design. In\napplications such those mentioned above, superconducting coils are always a key\ncomponent. For example, in a superconducting electric machine, the\nsuperconducting coils are used to generate the main flux density in the air\ngap, which is significantly important for the energy conversion. It is the\nperformance of the superconducting coils that plays an essential role in\ndetermining the performance of the device. However, the performance of a\nsuperconducting coil is limited by its critical current, which is determined by\ntemperature and the magnitude and orientation of the magnetic field inside the\nsuperconductors. Hence, in-depth investigations to estimate the critical\ncurrent of the superconducting coils are necessary before manufacturing.\nAvailable transient simulation models to estimate the critical current are\nthrough the H- and T-A formulations of Maxwell's equations. Both methods\nconsider the same current ramp-up process occurring in experiments. Besides\nthese transient models, static simulations can also be used: a modified\nload-line method and the so-called P-model, which is based on the asymptotic\nlimit of Faraday's equation when time approaches infinity. To find the best way\nto calculate the critical current, the four methods are used to estimate the\ncritical current of a double pancake superconducting coils and results are\ncompared with experiments. As a conclusion, T-A formulation, P-model, and the\nmodified load-line methods are recommended for estimating the critical current\nof the superconducting coils.\n