AC losses in stacked conductors exposed to external magnetic fields are numerically evaluated by means of a two-dimensional finite element method formulated using a self-magnetic field due to currents induced in an analysis region [1]. Fig. (a) shows the schematic illustration of two-dimensional numerical analysis model. The conductor is composed of two-ply coated conductor to improve the thermal stability. An idealized copper layer is sandwiched by a pair of superconducting layers in every conductor. On the other hand, Fig. (b) shows the simplified model to suppress the calculation time. The external magnetic fields are increased monotonically from zero so as to simulate the electromagnetic responses in several typical parts inside a pancake coil for high field magnet. In order to understand only the geometrical effects on the AC losses, the superconductors are assumed to be subject to the Bean model. The influences of the numbers of bundle conductors, the gaps between bundle conductors and the angles of applied magnetic fields on the AC losses are investigated numerically.

Keywords: AC loss, Finite element method, Magnetic interaction, Pancake coil