AC Loss Evaluation of Superconductor Strips Located Inside Iron Core Slots

AC losses in high temperature superconducting (HTS) windings located inside iron core slots are numerically evaluated by means of finite element methods. Two-dimensional cross sections in one of stator iron core slots with the HTS windings and gaps from rotor iron cores are modelled for numerical analyses. The HTS windings are composed of superconducting (SC) strips with an ignorable thickness stacked at even intervals to simulate single pancake coils wound using coated conductors. In this case, the SC strips can be formulated using the perpendicular component of a current vector potential. It is assumed that the transport property in the SC strips is subjected to Bean's critical state model, in which the critical current density is independent of the local magnetic field. In order to reflect boundary conditions surrounded by the iron cores into the numerical results effectively, vacuum regions around the HTS windings are formulated using a magnetic vector potential. Both the formulations are individually solved by exchanging necessary information with each other. The influences of the amplitude and frequency of applied transport current, the gap between the strips and the number of strips on the AC loss are investigated numerically.