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.

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Since many applications of YBCO tapes operate in external magnetic fields, it is necessary to investigate the magnetoangular dependence of critical current and n-values in coated conductors. In this paper, five commercial YBCO tapes with different microstructures produced by three different manufacturers are chosen. The selected samples have a width of 2.0, 4.0, 4.8, 6.0 or 12 mm, with copper, brass or stainless steel laminations. The critical current density dependence J c (B, θ) and n-values characteristics n(B, θ) of the tapes are comprehensively measured under various magnetic fields and orientations. Afterwards, the obtained experimental data sets are successfully fitted using a novel multi-objective model which considers the material anisotropy. By using this approach, a fitting function I c (B, θ) can always be obtained to accurately describe the experimental data, regardless of the fabrication and width differences of the superconducting tapes. Moreover, our experiment shows that when subject to different external magnetic fields, the angular dependence of n-values characteristics is directly correlated with the corresponding critical current profiles. Our results are helpful to predict the critical current of electromagnetically interacting 2G HTS wires, thereby improving the design and performance of the devices made from YBCO tapes.

This paper reports a newly developed high current transformer-rectifier High-T c Superconducting (HTS) flux pump switched by dynamic resistance. A quasi-persistent current of over 1.1 kA has been achieved at 77 K using the device, which is the highest reported operating current by any HTS flux pumps to date. The size of the device is much smaller than traditional current leads and power supplies at the same current level. Parallel YBCO coated conductors are used in the transformer secondary winding as well as in the superconducting load coil to achieve high current. The output current is limited by the critical current of the load rather than the flux pump itself. Moreover, at over 1 kA current level, the device can maintain high flux injection accuracy, and the overall flux ripple is less than 0.2 mili-Weber. The work has shown the potential of using the device to operate high field HTS magnets in ultra-high quasi-persistent current mode, thus substantially reducing the inductance, size, weight, and cost of high field magnets, making them more accessible. It also indicates that the device is promising for powering HTS NMR/MRI magnets, in which the requirement for magnetic field satiability is demanding.

Conductive‐bridging random access memory (CBRAM), dominated by conductive filament (CF) formation/rupture, has received much attention due to its simple structure and outstanding performances for nonvolatile memory, neuromorphic computing, digital logic, and analog circuit. However, the negative‐SET behavior can degrade device reliability and parameter uniformity. And large RESET current increases power consumption for memory applications. By inserting 2D material, molybdenum disulfide (MoS2), for interface engineering with the device configuration of Ag/ZrO2/MoS2/Pt, the negative‐SET behavior is eliminated, and the RESET current is reduced simultaneously. With the ion barrier property of MoS2, the CF can probably not penetrate the MoS2 layer, thus eliminating the negative‐SET behavior. And with the low thermal conductivity of MoS2, the internal temperature of the device would be relatively high at RESET, accelerating probably redox reactions. As a result, the RESET current is reduced by an order of magnitude. This interface engineering opens up a way in improving the resistive switching performances of CBRAM, and can be of great benefit to the potential applications of MoS2 in next‐generation data storage.

When a type II superconductor carrying a direct current is subjected to a perpendicular oscillating magnetic field, a direct current (DC) voltage will appear. This voltage can either result from dynamic resistance effect or from flux flow effect, or both. The temperature variation in the superconductor plays an important role in the nature of the voltage, and there has been little study of this so far. This paper presents and experimentally verifies a 2D temperature-dependent multilayer model of the second generation (2G) high temperature superconducting (HTS) coated conductors (CC), which is based on H-formulation and a general heat transfer equation. The model has coupled the electromagnetic and thermal physics, and it can simulate the behavior of 2G HTS coated conductors in various working conditions where the temperature rise has a significant impact. Representative electromagnetic phenomena such as the dynamic resistance effect and the flux flow effect, and thermal behavior like quench and recovery have been simulated. This thermal-coupled model is a powerful tool to study the thermal-electromagnetic behaviors of 2G HTS coated conductors in different working conditions, especially when the impact of temperature rise is important. This multilayer model is also very useful in analyzing the impact of different layers in the 2G HTS CCs, especially the metal stabilizer layers. It has been proven to be a very powerful tool to help understand more complicated characteristics in the CCs which could not be accurately measured or simulated by previous numerical models. The work is indicative and very useful in designing ac magnetic field controlled persistent current switches and flux pumps, in terms of increasing the off-state resistance, analyzing different sources of losses, minimizing detrimental losses, and enhancing the safety and stability.

This paper presents the measurement and simulation of Alternating Current (AC) losses on the Stabilizer-free and Copper Stabilizer High Temperature Superconducting (HTS) Tapes: SuperPower SF12100 and SCS12050. The AC loss measurement utilised electrical method to obtain overall losses with AC transport currents. The 2D H-formulation by COMSOL Multiphysics has been used to simulate the real geometry and multi-layer HTS tapes. Ferromagnetic AC losses of substrate have been assumed to be ignored as the substrates of SF12100 and SCS12050 are non-magnetic. Hysteresis AC losses in the superconducting layer, and eddy-current AC losses in copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from simulation, with 3 cases of different AC frequency 10, 100, and 1000 Hz. The eddy-current AC losses of copper stabilizer at frequency 1000 Hz were determined from both experiment and simulation. The estimation of AC losses with frequency at 10000 Hz was also carried out using simulation method. Finally, the frequency dependence of AC losses from Stabilizer-free Tape and Copper Stabilizer Tape were compared and analysed.

This article presents the power dissipation analysis on saturated iron-core superconducting fault current limiter (SISFCL). The modeling of SISFCL together with its power dissipation computation on high-temperature superconducting (HTS) coil were executed by the H-formulation model implemented into the finite-element method (FEM) software package COMSOL. The model was based on the practical threephase 35 kV/90 MVA SISFCL. The AC magnetic field in the crucial parts of SISFCL was studied to discover the origin of power loss on HTS coil. The instantaneous power dissipations in the HTS coil with increasing DC bias current were computed and compared. Analysis proved that power dissipation in the HTS coil of SISFCL should be taken into account for the real operation.  Index Terms-Saturated iron-core superconducting fault current limiter (SISFCL), High-temperature superconducting (HTS) coil, Power dissipation, AC loss, Finite element analysis.