Enhanced Model for Non-Insulated HTS Coils

Abstract

This paper addresses the topic of modelling 2 G HTS tapes and coils, especially (but not limited to) Non-Insulated (NI) devices. We propose a novel 3D electromagnetic Volume Integral Formulation (VIM) for homogenized coils. This model combines the flexibility of distributed circuit models with the numerical approach of Finite Element Methods (FEM). It offers some distinctive features if compared to already available integral formulations (such as Partial Element Equivalent Circuit): first, it describes the current vector potential T with quadratic shape functions, resulting in non-constant current densities J inside mesh elements. Secondly, it allows for homogenization of coil turns, together with arbitrarily curved geometries. The results of the model are verified against a COMSOL simulation. The discussion of the model includes also a fast current-sharing calculation in case of overcurrent, with the aim of providing comprehensive heat losses, to then feed thermal models. This work can contribute in better describing and understanding the behavior of NI coils under most operative conditions, expanding the capability of testing and diagnosing these devices.