Multiscale Method for AC Loss Calculation of HTS Coated Conductors With Magnetic Substrate

The ac loss calculation problem is the key issue for a superconducting magnet. The existing numerical models do not consider the magnetic properties of the substrate while calculating the transport ac loss of high temperature superconductor (HTS) coated conductors. In fact, the unacceptable time and memory consumption makes the ac loss calculation a tough task while considering the magnetic properties of the substrate. This paper introduces a two-dimensional multiscale method for calculating the transport ac loss of HTS YBCO coated conductors with magnetic substrate, which can greatly reduce the calculation time under the premise of high accuracy. The multiscale method is realized with three unidirectionally coupled models and only considers the nonlinear E-J characteristics in two simple models with fewer degrees of freedom, which avoids considering the E-J characteristics in the whole coil. The calculation accuracy of the multiscale method is validated by comparing the simulation results with that of Ainslie's model with the same coil structure, which consists of 2 × 50 turns of YBCO tapes with ferromagnetic substrate. The results of the multiscale method model are highly consistent with that of Ainslie's model. The calculation speed can be increased by two orders of magnitude with the multiscale method, which indicates that this method is an effective approach to handle the transport ac loss calculation problems while including the ferromagnetic substrate. It also has the ability to solve much more complex problems in the future, such as large-scale HTS magnet.