Modeling of coated conductor pancake coils with a large number of turns

Abstract

The current distribution, the magnetic field and the AC loss are numerically studiedfor pancake coils with up to 200 turns, taking into account the real thickness ofthe conductor and the magnetic interaction between the turns. All calculationsassume the critical state model with a constant critical current density. The resultsshow a slab-like current distribution, with the absence of magnetization currentsdue to the radial magnetic field. Consequently, longitudinal striation, with orwithout twisting, cannot reduce the self-field AC loss of this system. Finally,an analytical formula has been deduced for the AC loss at current amplitude:Im = Ic,where Ic is the critical current, for large mean coil radius and any number of turns.