Electromagnetic Characterisation and Modelling of Superconducting Wires and Coils for Engineering Applications

This thesis contributes to the broad understanding of the macroscopic electromagnetic behaviour of type-II superconducting wires (SC) under alternating and direct current (AC-DC) conditions, and the electromagnetic modelling of the second generation of high temperature superconducting (2G-HTS) coils for racetrack and pancake settings. In the first part, a comprehensive study of the effects of applying an AC transverse magnetic field to a type-II SC wire utilised for DC power transmission is presented. Likewise, the electromagnetic response of an AC superconducting wire that is simultaneously exposed to constant source (DC) of a transverse magnetic field has been analysed. Then, the second part deals with the study of the physical dependence of the hysteresis losses with the axial winding misalignment of superconducting racetrack and pancake coils subjected to AC applied transport current, made of commercial 2G-HTS tapes, which is a useful measure to understand the electromagnetic quantities of interest and the influence it could have on the coil performance in practical superconducting machines. Furthermore, the study is concluded with an exhaustive analysis of the impact of the material law selection on the numerical modelling of 2G-HTS tapes, which has allowed to establish a set of decision criteria that aims for the advising of computational modellers on what would be the most suitable material law in cases where, the need to quantify an electromagnetic quantity does not only depend on matching the experimental evidences, but where time and computing power are valuable resources to take into consideration. In summary, the undertaken studies focused on the local understanding of the physical properties of the wires and coils modelled, such as, the distribution of current density the resulting magnetic flux, magnetic moments, and the AC-losses, where the findings can be used as a practical benchmark to understand the electromagnetic features of superconducting wires under such AC-DC conditions, and the inherent physical characteristics of any 2G-HTS racetrack or pancake coil for engineering applications.