Electromagnetic-Thermal Finite Element Simulations of Superconductors Applied in Electrical Machines

The purpose of this thesis is to analyze, simulate, and experimentally verify the behavior of superconductors, materials of significant scientific interest and in ongoing research and development. Concerning the study of superconductivity, both finite element simulation and analytical analysis requires experimental calibration of the material properties This thesis’s work is focused in experimentally calibrating and optimizing these characterization methods. For this purpose simulations were conducted to analyze the electromagnetic behavior of two types of conductive tapes: copper and superconducting. These tapes were examined under two distinct thermal conditions—ambient temperature and immersion in liquid nitrogen. The simulations were carried out under both direct current (DC) and alternating current (AC) regimes. They were developed and verified, in order to draw important considerations for the work carried out. For model verification and calibration, experimental tests were carried in superconducting tapes to measure their resistivity characteristic in DC conditions. These experiments were then inserted as material properties in the FEM models. The macroscopic modelling approach is used in order to study and understand deeper the superconductivity, such as the A formulation or the T-A formulation. The primary objective of this study is to perform a comparative analysis between experimental and numerical results, with an emphasis on achieving optimal model fitting in direct current (DC). This was accomplished using targeted optimization algorithms implemented in Matlab, considering the variable of interest, in particular, the DC parameters of the superconductive tape and the law for the superconducting material considered in this study, a REBCO tape. The issue related to the losses in therms of electromagnetic heating has been discussed both for DC and AC currents, even compared to the traditional conductors. Ultimately, this study discusses the potential applications of superconductors in electrical machines, evaluating both the advantages and challenges associated with their use. Additionally, future perspectives in this field are explored.