Self-field Effects and AC Losses in Pancake Coils Assembled from Coated Conductor Roebel Cables

TL;DR

This paper presents a refined numerical model for pancake coils made from coated conductor Roebel cables, accounting for angular dependence of critical current density and 3D current lead shape, to better understand AC losses and self-field effects.

Contribution

It introduces a comprehensive 3D numerical model that includes angular dependence of Jc and detailed current lead geometry, improving accuracy over previous models.

Findings

Model accurately predicts AC losses in Roebel coil pancakes.

Current lead shape significantly influences measured AC losses.

Comparison with measurements validates the model's effectiveness.

Abstract

In this contribution we develop a refined numerical model of pancake coils assembled from a coated conductor Roebel cable, which includes the angular dependence of the critical current density $J_c$ on the magnetic field and the actual (three-dimensional) shape of the current lead used to inject the current. Previous works of ours indicate that this latter has an important influence on the measured value of the AC losses. For the simulation of the superconductor, we used two alternative models based on different descriptions of the superconductor's properties and implemented in different mathematical schemes. For the simulation of the current lead we use a full three-dimensional finite-element model. The results of the simulation are compared with measurements and the main issues related to the modeling and the measurement of Roebel coils are discussed in detail.