Contact Resistance Dependent Transient Loss of REBCO No-Insulation Magnet UsingT-AFormula During Ramping Process

Abstract

The transient loss during the ramping process is an important evaluation metric for commercial large-scale magnet systems to meet refrigeration requirements; this loss is considerably influenced by contact resistivity. Due to the intrinsic bypass current of the no-insulation pancake, two parts of the transient loss were considered in this study: turn-to-turn loss generated by the radial direction current and the magnetization loss produced by the azimuthal direction current. A turn-distributed model was used to calculate the non-uniform current distribution, where the pancake coil is radially subdivided into each turn. The radial current was used to calculate the turn-to-turn loss. The turn azimuthal current was applied to the boundary condition of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T-A</i> formula to calculate the magnetization loss in a cylindrical coordinate system. The superconductor index value model was used for the simulations, where the critical current density is the conductor engineering current density estimated by a neural network fitting model. The contact resistance dependent turn-to-turn loss and magnetization loss were presented. This approach is expected to be used in magnet-level NMR/ MRI systems.