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The development of high-temperature superconducting (HTS) electrical machines results in applications of various fields, as they have higher efficiency and power density. Numerical modeling of superconducting electrical machines is usually performed by finite element method based their electrical behavior, and H-Formulation of the Maxwell's equations is one of the models that are used tremendously due to its high flexibility and simplicity. Axial field machine (AFM) is a machine topology with higher efficiency and power density, but with more complexity when modeling. This paper proposed a new 2D model for the superconducting AFM, where the superconducting coil is simulated with a 2D infinitely long model, this model also divides the electrical machine into two parts: the superconducting parts (HTS coils, bulks, etc.) and non-superconducting parts (e.g., conventional conductors, machine structure). This paper compares the results of H-A Formulation and T-A Formulation with this approach, which requires appropriate boundary conditions and continuity between the two regions, along with correct modeling of fixed and moving parts of the electrical machine, where the geometry of this model is based on a linear synchronous machine, which means the rotor is moving linearly instead of rotation. [ABSTRACT FROM AUTHOR]

Different from many superconducting magnet designs based on the analytical algorithm and finite element method (FEM), this article presents an intelligent design of the SMES and high-field magnet using the self-programmed graphical user interface (GUI). As the important basis, the analytical solutions of SMES magnet are developed for calculating the magnetic field, inductance and critical current, whose accuracies are also verified by the experiment. Then, the analytical solutions are merged into the GUI tool with multi-window interface based on the MATLAB. The new platform is built to offer scientists and engineers a smart tool to design and optimize SMES magnets to reach the maximum energy capacity. After the structural optimization of a MJ-class SMES magnet, the critical current and energy capacity improve by 20.46% and 38.67%, respectively. Compared to previous superconducting magnet designs, this new platform for the SMES and high-field magnet design has the advantages of diverse HTS tape/magnet structure selections, user-friendly interface, automatic optimization, and fast speed. [ABSTRACT FROM AUTHOR]

Experimental and advanced superconducting Tokamak (EAST) was designed by the Institute of Plasma Physics Chinese Academy of Sciences. The magnet system of EAST includes poloidal field (PF) coils, central solenoid (CS) coils, and toroidal field coils. The heat generated by the ac losses of PF and CS coils increases the burden of the cooling system, which reduces the critical current of the superconducting cable. Once the superconducting magnet quenches, it will pose a serious threat to the stability of the whole device. In this paper, the piecewise linear method and the finite-element analysis were used to analyze the ac loss of the EAST PF and CS coils under the specific operating current. The whole calculation process is described in detail. The final results meet the stability margin of the design of the EAST device. Meanwhile, the ac losses of PF and CS coils for EAST are theoretically evaluated in terms of the structure of magnet, the simplified current, and the distribution of the coil. The results of this paper not only provide data support for the next design and experiment of the EAST device, but provide some references for similar calculation of other large nuclear fusion magnets. [ABSTRACT FROM AUTHOR]

This paper presents the concept of using horizontally parallel HTS tapes with AC loss study, and the investigation on possible wireless power transfer (WPT) applications. An example of three parallel HTS tapes was proposed, whose AC loss study was carried out both from experiment using electrical method; and simulation using 2D H -formulation on the FEM platform of COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil was simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrates that HTS parallel tapes could be potentially used into wireless power transfer systems, which could have lower total AC losses than conventional HTS coils. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on ac losses of superconducting bulk with the help of finite element software of Comsol Multiphysics. The calculation ac loss result was compared with that from analytical formulas for type-II superconducting slab and cylinder. Three different geometries of the columnar bulk are analyzed, which are bulk with no core, bulk with a central columnar air core, and bulk with a central columnar iron core. The core is parallel to the c-axis of bulk. The temperature dependence of the ac loss is presented, and the thermal behavior of the bulk is analyzed by associating ac loss with heat transfer characteristic through the external surface of the bulk sample. [ABSTRACT FROM AUTHOR]

The dynamic voltage is a unique phenomenon of superconducting materials. It arises when the superconductor is carrying a DC transport current and spontaneously in subject to an AC magnetic field. This study excavates the aspects that previous studies have not comprehensively investigated: the dynamic voltage in a DC-carrying superconducting tape exposed to different oscillating AC magnetic fields. First, the fundamental physics of dynamic voltage/flux of superconductors is reviewed and further analysed in detail. We used the superconducting modelling method using the H-formulation merged into the finite-element method (FEM) software, to re-produce the typical dynamic voltage behaviour of a superconducting tape. The modelling was verified by both the analytical and experimental results, in order to precisely prove the reliability of the modelling. Afterwards, the modelling was performed for a DC-carrying superconducting tape under four different oscillating magnetic fields (sine, triangle, sawtooth and square), and their corresponding dynamic voltages and energy losses were analysed and compared. Results show the sinusoidal magnetic field can lead to the optimal combination of reasonable dynamic voltage but relatively lower loss, which is suitable for those superconducting applications requiring dynamic voltage as the energy source, e.g., flux pumps. This article presents novel investigation and analysis of the dynamic voltage in superconducting materials, and both the methodology and results can provide useful information for the future design/analysis of superconducting applications with DC transport currents and AC magnetic fields. [ABSTRACT FROM AUTHOR]

The high-temperature superconductor (HTS) has been recognised as one of the most up-and-coming materials thanks to its superior electromagnetic performance (e.g., zero resistance). For a high-speed maglev, the HTS magnet can be the most crucial component because it is in charge of both the levitation and the propulsion of the maglev. Therefore, a fundamental study of HTS magnets for maglev is crucial. This article presents the fundamental design and modelling of the superconducting magnet for a high-speed maglev, including mechanics, electromagnetics, and loss analysis during instability. First, the measurements of the superconducting wire were performed. The HTS magnet was primarily designed and modelled to fulfil the basic electromagnetic requirements (e.g., magnetic field) in order to drive the maglev at a high speed. The modelling was verified by experimental tests on a scale-down HTS magnet. A more professional model using the H-formulation based on the finite element method (FEM) was built to further investigate some deeper physical phenomenon of the HTS magnet (e.g., current density and loss behaviours), particularly in situations where the high-speed maglev is in the normal steady state or encountering instability. [ABSTRACT FROM AUTHOR]

The superconducting fault current limiter (SFCL) has been regarded as one of most popular superconducting applications. This article reviews the modern energy system with two major issues (the power stability and fault-current), and introduces corresponding approaches to mitigate these issues, including the importance of using SFCL. Then the article presents the experiment of a resistive-type SFCL used for a power electronic circuit. The experiment well matched the advanced finite-element method (FEM) SFCL model, from which the reliability of FEM SFCL model was confirmed. Afterwards, the FEM model and the power system software PSCAD were used to model a large-scale resistive-type SFCL. Under the same simulation conditions the FEM model well matched the PSCAD model. The FEM method has the advantages of offering specific electromagnetic modeling on superconducting part. The PSCAD SFCL model has much faster simulation speed and can directly cope with all ranges of power networks. This article presents a new vision and an all-in-one study to link the experiment, the numerical model, and the power/energy system software model, and their agreement can be extremely helpful for researchers and engineers to find useful evidences and reliable methods to confidently carry out successful SFCL designs for the electrical energy system. • An all-in-one study to link the experiment, FEM, and energy system model of SFCL. • Experiment of a resistive-type SFCL was carried out for a power electronic circuit. • Advanced FEM model of SFCL well matches the experiment. • SFCL model using power/energy system software well matches the FEM SFCL model. • Agreement of these methods is extremely helpful to a successful SFCL design. [ABSTRACT FROM AUTHOR]

In order to fabricate high-current superconducting conductors for engineering applications, the configuration of stacked high-temperature superconductor (HTS) strips is one of the most popular choices. AC losses in HTS stacks have been vastly studied, but the economic study towards the AC losses with respect to the capital investment and operating costs of HTS stacks is still missing. First, the modelling strategy using the finite element method (FEM) based on the H -formulation is explained, and the basic AC loss simulation of a single strip is verified by the Norris analytical methods. The HTS stack (16 strips) is used as an example, and the corresponding current distribution and magnetic field are analyzed. The relationship between the AC loss and current-carrying capability is studied for multiple stacks with different numbers of strips. Economic analysis is performed with regard to the relationship between the AC losses and investment/operating costs of multiple stacked HTS strips. In this article, the numerical modeling together with the economic analysis of stacked HTS strips bring new visions, which can be beneficial for the future designs of high-current superconducting conductors and cables. [ABSTRACT FROM AUTHOR]

Polymeric composites with thermally conductive hybrid fillers are significant in the electronics and thermal dissipation, where thermal transport along with multifunctionality is required to meet the application needs. Introduction of hybrid fillers would induce multiple interface scattering and rational design on the filler contact should be the critical criteria, while there is insufficient principle. To promote the thermal transport capability, in this paper, a contact probability model has been established to quantitatively analyze the thermal conductivity and contact probability in the silicone rubber composites with hybrid fillers (including various aluminium oxides and silicon carbide whisker). The results from experiment and simulation suggest that three critical parameters, i.e. volume fraction, filler shape and filler size, are the essential factors of hybrid fillers on impacting the thermal conductivity of composites. With understanding the contact types of hybrid filler, the optimized thermal conductivity has been obtained in the composites with aluminium oxides and silicon carbide whisker fillers. The model and analysis here have provided new contact mechanism for understanding the thermal transport in composites, which could be extended to rationally design and fabricate other types of polymeric composites with hybrid fillers. [ABSTRACT FROM AUTHOR]

When a REBCO tape carrying DC transport current is exposed to a perpendicular AC magnetic field with amplitude above certain value, flux could be triggered to traversing the superconducting tape. During the process, a biased DC response voltage, called the dynamic resistance voltage will be induced. In the paper, the calculation on the time-dependent dynamic resistance voltage was carried out by the H -formulation model implemented in the finite-element method (FEM) software package COMSOL Multiphysics. Fourier analysis on the waveform of dynamic resistance voltage was utilized to figure out the main components of the response voltage. The DC component, second harmonic component and ratio of the two components can reflect how the instantaneous dynamic resistance responds to the applied AC magnetic field and the DC transport current. The findings in the paper can be used to monitor the state of DC-carrying REBCO tapes subject to an AC magnetic field. [ABSTRACT FROM AUTHOR]

• A numerical model of periodically arranged HTS tapes using the finite element method (FEM). • Distributions of the magnetic field and current of HTS tapes by periodical arrangements. • Differences between the FEM results and analytical models from periodically arranged HTS tapes. • Mathematical models for the AC loss in periodically arranged HTS tapes. • An effective method to optimize the electromagnetic environment for periodically arranged HTS tapes and estimate the AC loss. The practical operation of a high-temperature superconducting (HTS) tape to form a HTS device is strongly related to the HTS tape electromagnetic environment in the device. With regard to the HTS tapes commonly stacked for practical applications, it is necessary to study the electromagnetic interaction of the proximity HTS tapes to design and optimize the HTS tapes and devices. This paper presents a numerical model of periodically arranged HTS tapes using the finite element method (FEM). The numerical method has been developed to build the equivalent periodical arrangement of infinite HTS tapes and applied to simulate two basic arrangements, horizontal and vertical periodical arrangements. The magnetic field and current distributions of HTS tapes by periodical arrangements have been investigated. The effects on critical current with different arrangements have been illustrated. It is found that the Y-stack can reduce the current carrying capacity while the X-array can increase that in comparison to a single tape. The differences between the FEM results and analytical models have been analysed and also compared with the Norris model. The two mathematical models derived for AC loss prediction have shown higher accuracy than the existing analytical models. This study presents an effective method to optimize the electromagnetic design by considering favorable structure or environment for the stacked HTS tapes and estimate the AC loss, shows the phenomenon of central tapes in an HTS array, which could be further used in performance analysis of superconducting devices, e.g. HTS transformers. [ABSTRACT FROM AUTHOR]