Study on the AC Loss Reduction of REBCO Double Pancake Coil

The numerical study on the transport loss reduction in REBCO double pancake (DP) coil is presented in this paper. An axisymmetric finite element model based on H formulation and E-J power law is established. The influence of the gap between two pancakes on the transport losses of DP coils is investigated. The use of magnetic flux diverters to reduce the ac loss of the DP coil by decreasing the perpendicular magnetic field applied to the tape surface is also studied. It is found that the perpendicular magnetic field is decreased clearly by attaching the flux diverter in the middle and end positions of DP coil. Compared with the ac losses of DP coils without flux diverters, the use of flux diverters can decrease the ac losses by 70% when the applied current is at half the critical current of DP coil.