Power dissipation in HTS coated conductor coils under the simultaneous action of AC and DC currents and fields

Abstract

This paper presents a comprehensive AC loss study of a circular HTS coil. The AC losses from a circular double pancake coil were measured using the electrical method. A 2D axisymmetric H-formulation model using FEM package COMSOL Multiphysics has been established, which was able to make consistency with the real circular coil used in the experiment. To model a circular HTS coil, a 2D axisymmetric model provided better accuracy than a general 2D model, and was also more efficient than a 3D model. Three scenarios have been analysed: Scenario 1 AC transport current and DC magnetic field (experiment and simulation); Scenario 2 DC transport current and AC magnetic field (simulation); Scenario 3 AC transport current and AC magnetic field (simulation and experimental data support). The angular dependence analysis on the coil under the magnetic field with the different orientation angle  has been carried out for all three scenarios. For Scenario 3, we investigated the effect of relative phase difference ∆ between AC current and AC field on the total AC loss of the coil. To summarise, we have carried out a current/field/angle/phase dependent AC loss (I, B, , ∆) study of circular HTS coil, which could potentially benefit the future design and research of HTS AC systems.

Investigation on Power Dissipation in the Saturated Iron-Core Superconducting Fault Current Limiter

“…There were two possible reasons why the loss massively increased with higher DC bias current: (i) higher DC bias current generated more self-field which could further decrease critical current of the HTS coil; (ii) dynamic resistance loss increased more with higher DC bias current. Similar phenomenon can be found in [33].…”

Review of the AC loss computation for HTS using H formulation

“…Both the single tape losses from experiment and H-formulation are between the Norris strip and Norris ellipse. The AC losses in the HTS tapes and coils in the presence of AC magnetic field can be accurately modeled by H-formulation, and also agree well with the Brandt analytical solution and experiment results [29,30]. Overall, these are good examples to prove that measurement, analytical solution, and FEM based on H-formulation are well consistent with each other.…”

“…Almost at the same time Brambilla et al independently carried out the first comprehensive study on the HTS AC loss calculation using the H-formulation, together with the theoretical derivation and comparison with the Norris and Brandt analytical solutions [20]. Figure 2 presents a recent study of ours on the AC losses in a single HTS tape and an HTS coil made with the same material (SuperPower SCS6050), with the AC transport current [29]. Results show that the losses both from single tape and coil are frequency independent in the range 50 Hz to 200 Hz, and both of them match with the loss results from H-formulation.…”

Local electromagnetic properties and hysteresis losses in uniformly and non-uniformly wound superconducting racetrack coils

“…High temperature superconducting coils with Rare-Earth Barium-Copper-Oxide (Re-BCO) coated conductors are the cornerstone of nearly all current and envisaged high-power density applications taking advantage of the local electromagnetic properties of type-II superconductors [1][2][3][4][5][6] . Attaining a clear understanding of the physical and designing parameters that might render to the minimization of AC losses in these systems is, by default, one of the most important subjects in the physics and engineering of applied superconductivity.…”

“…Attaining a clear understanding of the physical and designing parameters that might render to the minimization of AC losses in these systems is, by default, one of the most important subjects in the physics and engineering of applied superconductivity. [6][7][8][9][10][11][12] However, despite many experimental and theoretical studies have been performed on the AC losses of HTS racetrack coils, [13][14][15][16][17] these always assume that the coil is perfectly wound, neglecting thence any influence of a possible misalignment between the coil turns (tapes), a situation that is likely to happen either during the coil manufacturing, their assembling in practical applications, or even due to possible axial alterations caused by extrinsic magnetic, thermal, or mechanical pressure over the coil turns. In fact, despite than in the last two decades the applied superconductivity field has experienced a significant increase in the physical understanding of the local electromagnetic properties of type II superconductors, including the second generation of high temperature superconducting (2G-HTS) tapes, it is the high aspect ratio of the 2G-HTS tapes what from the computational perspective is still imposing significant challenges to understand their performance in practical superconducting machines.…”