Detailed numerical simulations can assist in the design and analysis of superconducting coils. In recent years the advent of the No-Insulation High-Temperature Superconducting (NI-HTS) coils technology, has increased the need for new simulation tools to accurately predict their response in typical operating conditions.

A detailed knowledge of the current distribution in NI-HTS coils is essential to compute the magnetic field profile generated by the coil, investigate the mechanical stress due to Lorentz forces and the losses in electrodynamic transient. Many circuit models proposed in the literature can describe the current flowing in the radial direction of an NI-HTS coil, but very few can describe the behavior of both the shielding currents in the tape and the radial currents.

This work aims to a lumped parameter circuit model suitable for an in-depth analysis of the current distribution inside a NI-HTS coil. The lumped parameters circuit model proposed in this work can compute the current distribution in both the radial and azimuthal directions inside the coil as well as the magnetization currents arising inside the REBCO tapes.

To compute the distribution of the shielding currents and their impact on AC losses, the tape composing each turn is discretized across its width with a number of sub-elements, each represented through a different circuit component. The model was compared with 2D FEM simulation and an analytical formula to asses its ability in evaluating the screening currents in the case of a single tape.

Although this work is aimed at the study of layer wound NI-HTS coils, the model described can be applied to the study of tapes, stacks of tapes, or pancake coils just by modifying the topology of the network.