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Flux penetration and AC loss are among the key problems in the application of high-temperature superconductors (HTSs). Through simulation, the value and distribution of AC loss in HTS equipment can be evaluated and optimized in the design stage, so as to ensure the reliability and stability of the equipment. At present, there are many algorithms for AC loss calculation that can be simplified to a two-dimensional model, but for the case of three-dimensional structure such as cable in a spiral structure, there are still some problems such as difficult meshing, difficult convergence, and low efficiency. In this paper, an upgrade of the two-dimensional J model to a three-dimensional J model is proposed, permitting effective calculation of the flux penetration and AC loss in the CORC cable. The reliability of the method is verified by comparing the calculated results with the analytic model and with experimental results. At present, this method can efficiently calculate a 3D CORC model with a total of 15 superconducting tapes in five layers. Also discussed is the feasibility of upgrading to calculate larger models.

The flux motion and its collective behaviour known as AC loss is the basic characteristic of high temperature superconducting (HTS) materials and controls the economic efficiency, stability and magnetic field uniformity of superconducting equipment. In so far, we have no method to calculate the AC loss of HTS devices in an efficient way. Normally, it will take days to simulate AC loss of HTS coils even with moderate number of turns. In this paper, we surprisingly found that an integral method is remarkably efficient in calculating AC loss of the coils in large scale. By comparing with the fastest method at present, the integral method is proved to be 4.4 times faster than the present one. We give the calculation details and discuss why this method has an advantage in calculating AC loss of the coil with a large number of turns.