Showing papers in "IEEE Transactions on Applied Superconductivity in 2018"

SMES-Battery Energy Storage System for the Stabilization of a Photovoltaic-Based Microgrid

Abstract: As superconducting magnetic energy storage (SMES) and battery are complementary in their technical properties of power capacity, energy density, response speed, etc., this paper proposes an SMES-battery energy storage system to stabilize a photovoltaic-based microgrid under different faults. The related theoretical modeling is stated, and the control and coordination methods of the SMES-battery are put forward. Using MATLAB, a comparison of with the SMES-battery and only with the battery is carried out. From the main specifications of the SMES magnet, the ac-loss calculation is also performed. The results show that i) the SMES-battery is better than the battery to timely deal with the transient faults of the microgrid; ii) the SMES-battery enables to ensure a seamless mode-transition for the microgrid under the external fault, and reduce the fault current in the point of common coupling to avoid an unnecessary off-grid under the internal fault; and iii) the SMES magnet's ac-loss power has a maximum value of 380 W, and it is acceptable for the future design of conduction-cooled structure and cryogenic system.

Stability Improvement of DC Power Systems in an All-Electric Ship Using Hybrid SMES/Battery

Abstract: As the capacity of all-electric ships (AESs) increases dramatically, the sudden changes in the system load may lead to serious problems, such as voltage fluctuations of the ship power grid, increased fuel consumption, and environmental emissions In order to reduce the effects of system load fluctuations on system efficiency, and to maintain the bus voltage, we propose a hybrid energy storage system (HESS) for use in AESs The HESS consists of two elements: a battery for high energy density storage and a superconducting magnetic energy storage (SMES) for high power density storage A dynamic droop control is used to control charge/discharge prioritization Maneuvering and pulse loads are the main sources of the sudden changes in AESs There are several types of pulse loads, including electric weapons These types of loads need large amounts of energy and high electrical power, which makes the HESS a promising power source Using Simulink/MATLAB, we built a model of the AES power grid integrated with an SMES/battery to show its effectiveness in improving the quality of the power grid

A General Method to Simulate the Electromagnetic Characteristics of HTS Maglev Systems by Finite Element Software

Abstract: For practical maglev systems, the mutual effects among the bulk superconductor and the permanent magnet are primarily investigated to provide useful implications for the design. This paper proposed a general simulation method to demonstrate the electromagnetic behaviors of a levitation system. The basics properties including the distributions of the induced current and the levitation/guidance force of a bulk superconductor have been calculated while moving in the nonuniform magnetic field generated by a permanent magnet guideway. This numerical method is based on solving the partial differential equations time dependently and adapted to the commercial finite element software COMSOL Multiphysics 5.3. It is worth mentioning that relative movements are solved to simulate more real test scenarios with the moving mesh and automatic remeshing in COMSOL. Simulation results are intuitive for the generation of electromagnetic behaviors and show a good consistency with previous experimental data. We conclude that this simulation method can be a powerful tool for researchers and engineers to investigate analogous problems with a greater level of flexibility and expandability.

Fault Ride-Through Enhancement of PMSG Wind Turbines With DC Microgrids Using Resistive-Type SFCL

Abstract: Integrating permanent magnet synchronous generator (PMSG) wind turbines with DC microgrids have attracted a great attention due to the inherent merits of DC systems. However, under the fault conditions, the excessive energy during fault will be reflected on PMSG rotating parts causing overspeed, mechanical stresses, and fast aging. Also, large fault currents will force generator-side converter to disconnect making it not complied with grid codes. Accordingly, this paper aims to apply superconducting fault current limiter (SFCL) to enhance the performance of PMSG wind turbines with DC microgrids under the fault conditions. PSCAD/EMTDC software is used to build the system under study that includes PMSG, controlled AC/DC converter, SFCL, and DC bus. The behavior of SFCL in enhancing the DC output of the converter is first studied. Then, the impact of using SFCL on the speed, torque, and output current of PMSG is investigated and discussed. Finally, the suitable current limiting resistance is adopted considering DC output as well as PMSG speed.

Feasible Application Study of Several Types of Superconducting Fault Current Limiters in HVDC Grids

Abstract: The eventual goal of high-voltage direct-voltage (HVDC) systems is to implement HVDC grids. One of the key obstacles in realization of the HVDC grid is the absence of a dc circuit breaker (DCCB). Several prototypes of DCCBs for the HVDC grid have been proposed, but no commercial solution has been developed yet due to insufficient dc fault current breaking capabilities and an unreliable protection-coordination scheme. In this respect, application of the suitable fault current limiter is necessary, and the use of a superconducting fault current limiter (SFCL), which has already been developed for the ac grid, is a viable solution, but there is no fundamental research about performance evaluation of SFCLs for the dc grid. Therefore, we aim to verify the applicability of the conventional SFCL in HVDC grids and perform a comparative analysis of the performance of several types of SFCLs. To analyze the performance of the conventional SFCL in the HVDC grid, three well-known representative types of SFCLs are modeled in MATLAB/Simulink, and their current limiting and recovery characteristics and energy dissipation are examined in voltage-source converter HVDC system application. From the simulation results, we deduced the strengths and the weakness of different types of SFCLs. Consequently, the likely SFCL candidate for commercialization in dc grid applications is suggested.

Single Photon Counter Based on a Josephson Junction at 14 GHz for Searching Galactic Axions

Abstract: Axions and axion-like particles appear in well-motivated extensions of the standard model of particle physics and may be the solution to the long-standing puzzle of the dark matter in our Universe. Several new experiments are foreseen in the next decade searching them in a wide range of the parameter space. In the mass region from few to several tens of microelectronvolt, detector sensitivity will be limited by the standard quantum limit of linear amplifiers and a new class of single microwave-photon detector will be needed. We have developed a single photon counter based on the voltage switching of an underdamped Josephson junction that is coupled to a coplanar waveguide. By measuring the switching voltage, we can register single photons at 14 GHz with the rate less than 1 photon per 3000 s.

Superconductor Electronics Fabrication Process with MoNx Kinetic Inductors and Self-Shunted Josephson Junctions

Abstract: Recent progress in superconductor electronics fabrication has enabled single-flux-quantum (SFQ) digital circuits with close to one million Josephson junctions (JJs) on 1-cm 2 chips. Increasing the integration scale further is challenging because of the large area of SFQ logic cells, mainly determined by the area of resistively shunted Nb/AlO x -Al/Nb JJs and geometrical inductors utilizing multiple layers of Nb. To overcome these challenges, we are developing a fabrication process with self-shunted high-J c JJs and compact thin-film MoN x kinetic inductors instead of geometrical inductors. We present fabrication details and properties of MoN x films with a wide range of T c , including residual stress, electrical resistivity, critical current, and magnetic field penetration depth λ 0 . As kinetic inductors, we implemented Mo 2 N films with Tc about 8 K, λ 0 about 0.51 μm, and inductance adjustable in the range from 2 to 8 pH/sq. We also present data on fabrication and electrical characterization of Nb-based self-shunted JJs with AlOx tunnel barriers and Jc = 0.6 mA/μm 2 , and with 10-nm thick Si 1-x Nbx barriers, withx from 0.03 to 0.15, fabricated on 200-mm wafers by co-sputtering. We demonstrate that the electron transport mechanism in Si 1-x Nbx barriers at x <; 0.08 is inelastic resonant tunneling via chains of multiple localized states. At largerx, their Josephson characteristics are strongly dependent onx and residual stress in Nb electrodes, and in general are inferior to AlO x tunnel barriers.

Comparison of Levelized Cost of Energy of superconducting direct drive generators for a 10 MW offshore wind turbine

Abstract: A method for comparing the levelized cost of energy (LCoE) of different superconducting drive trains is introduced. The properties of a 10-MW MgB2 superconducting direct-drive generator and the cost break down of the nacelle components are presented and scaled up to a turbine with a rotor diameter of up to 280 m. The partial load efficiency of the generator is evaluated for a constant cooling power of 0, 50, and 100 kW, and the annual energy production is used to determine the impact on the LCoE.

The EuCARD2 Future Magnets Program for Particle Accelerator High-Field Dipoles: Review of Results and Next Steps

Abstract: The EuCARD2 collaboration aims at the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, to be tested in small coils and magnets capable to deliver 3-5 T when energized in stand-alone mode, and 15-18 T when inserted in a 12-13 T background magnet. REBCO tape, assembled in a Roebel cable, was selected as conductor. The developed REBCO tape has reached a record engineering critical current density, at 4.2 K and 18 T of ${\text{956 A/mm}}^{2}$ . Roebel cable carried up to 13 kA at 20 K when tested in a small coil (FeatherM0.4). Then a first dipole magnet, wound with two low-grade Roebel cables of 25 m each, was assembled and tested. The dipole reached the short sample critical current of 6 kA generating more than 3 T central field at about 5.7 K, with indications of good current transfer among cable strands and of relatively soft transition. The construction of a costheta dipole is also discussed. Eucard2 is reaching its objective and is continuing with the H2020-ARIES program aiming at doubling the Je at 20 T to obtain 6 T as standalone and 18 T as insert in a high field facility.

Digital Superconducting Electronics Design Tools—Status and Roadmap

Abstract: At the start of the most ambitious development program for superconducting electronics circuit design tools to date-the IARPA SuperTools Program-we compile a comprehensive overview of the state of design tool development and use in the superconducting electronics community. Earlier design software roadmaps and tools were focused heavily on the device and gate level, with reasonably simple synthesis at the level of thousands of gates. Today, this is mostly still adequate for analog circuits, but completely inadequate for very large scale integration digital systems. Superconducting electronics circuit design tools today are still fragmented, incomplete, and insufficient for the design of very large scale integration circuits. Electronic design tools should enable design and verification of integrated circuits from process modeling right up to full system yield and reliability modeling. Progress and requirements to bring about sophisticated design tools are discussed.

Analysis of Electromagnetic Force and Deformation Behavior in Electromagnetic Tube Expansion With Concave Coil Based on Finite Element Method

Abstract: At present, the cylindrical coil is used to generate the electromagnetic force in electromagnetic tube expansion process. The obtained radial electromagnetic force in the end of the tube is less than the one in the middle of the tube for the end effects. Hence, the tube deformation is inhomogeneous in the axial direction. This paper presents a method named electromagnetic tube expansion with a concave coil to obtain more homogeneous deformation. By using COMSOL software, it gives the simulations for the effect of the geometry parameters of the concave coil on the distribution of the radial electromagnetic force and deformation behavior for the given AA6063-T6 tube. Simulations show that the concave coil with suitable parameters can obtain the homogeneous deformation. Furthermore, the homogeneous deformation range obtained by the concave coil is 36 mm, which is better than the obtained range by the cylindrical coil.

Rotor Design of High-Speed Permanent Magnet Synchronous Motors Considering Rotor Magnet and Sleeve Materials

Abstract: This paper describes the rotor design of high-speed permanent magnet (PM) synchronous motors considering rotor magnet and sleeve materials. The influence of four different sleeve materials with two different PM materials on the mechanical stress of a high-speed PM rotor is presented, and the relationship between sleeve thickness and shrink fit is examined. Rotor design criteria according to rotor materials are described by an analytical method. The proposed method is validated by an actual operational test at 400000 rpm using a fabricated prototype rotor.

Design and Performance of a ``Squirrel-Cage'' Dynamo-Type HTS Flux Pump

Abstract: Dynamo-type high-temperature superconductor (HTS) flux pumps are fully superconducting dc current sources for HTS magnet coils, which eliminate the need for external current leads. Previous work has focussed on dynamos employing a single-coated conductor stator wire, and the maximum output current is found to be limited by the effective internal resistance of the stator wire. It is expected that adding additional stator wires in parallel will increase the maximum output current. However, there have been few experimental reports of this effect, nor of the influence of the rotor magnet configuration in a multiply parallel stator arrangement. In this paper, we report on the design and experimental characterization of an HTS dynamo employing eight parallel HTS stator wires, which are arranged in a cylindrical geometry and excited by an axially concentric rotor carrying one or more permanent Nd-Fe-B magnets. We investigate the effect of changing the number of rotor magnets, and find that the maximum output current is achieved when the number of rotor magnets is less than half the number of stator wires. We have demonstrated output currents of up to 700 A from this device. This is the highest reported output to date from a flux pump operating at liquid nitrogen temperatures. Furthermore, our results indicate that the squirrel-cage architecture used here is capable of achieving a maximum output current of ~ 1.3 kA. At present, the heat load associated with a kA+ conduction cooled current leads prevents such large currents being injected into present-day cryo-cooled HTS magnets. Our results now indicate that this issue could be circumvented through employing an HTS dynamo, opening up new opportunities to consider novel designs of very high-current cryo-cooled HTS magnets.

Status of the 16 T Dipole Development Program for a Future Hadron Collider

Abstract: A next step of energy increase of hadron colliders beyond the LHC requires high-field superconducting magnets capable of providing a dipolar field in the range of 16 T in a 50-mm aperture with accelerator quality. These characteristics could meet the requirements for an upgrade of the LHC to twice the present beam energy or for a 100-TeV center of mass energy future circular collider. This paper summarizes the activities and plans for the development of these magnets, in particular within the 16 T Magnet Technology Program, the WP5 of the EuroCirCol, and the U.S. Magnet Development Program.

Electromagnetic Design of Superconducting Synchronous Motors for Electric Aircraft Propulsion

Abstract: This paper evaluates the electromagnetic characteristics as to two types of superconducting motors: one is the superconducting motors adopting high-temperature superconducting field coils and copper armature windings; and the other is fully-superconducting motors, which have high-temperature superconducting field coils and MgB 2 superconducting armature windings. Analytical formulas and FEM are employed for the designs of 1.5-, 3.0-, and 5.0-MW motors. We consider how to reduce ac loss in MgB 2 winding structure as well. The analysis of our results, which was conducted mainly over output density and efficiency, suggests that the adoption of superconducting motors is more realistic in realizing electrical aircraft propulsion system in terms of higher output; the analysis results show that the fully-superconducting motors have a potential to reach over 16 kw/kg.

Design of a 20 MW fully superconducting wind turbine generator to minimize the levelized cost of energy

Abstract: Superconducting machines are promising candidates for direct-drive multimegawatt offshore wind turbines. Here, we designed a 20-MW fully superconducting synchronous wind turbine generator using magnesium diboride (MgB 2 ) superconductors for both rotor and stator windings. MgB 2 tapes operating at 10 K are used for the rotor windings in order to improve the packing factor. A Rutherford cable made of 91-filament MgB 2 wires operating at 20 K is used for the stator windings in order to limit the ac losses. Two separate cryostats are considered for the stator and the rotor to increase the system reliability. Besides, to reduce the machine's weight and to simplify the cryogenic system, a toothless magnetic circuit is adopted. The goal of the two-dimensional finite element method based optimization was to minimize the levelized cost of energy (LCOE). Numerical results show that the adopted topology is lightweight enabling to reduce the cost of the nacelle, tower, and foundation, and therefore, the LCOE in comparison to a conventional generator. But the ac losses are significant, requiring at this stage of the study an impractical number of cryocoolers.

Coupling of Magnetothermal and Mechanical Superconducting Magnet Models by Means of Mesh-Based Interpolation

Abstract: In this paper, we present an algorithm for the coupling of magnetothermal and mechanical finite element models representing superconducting accelerator magnets. The mechanical models are used during the design of the mechanical structure as well as the optimization of the magnetic field quality under nominal conditions. The magnetothermal models allow for the analysis of transient phenomena occurring during quench initiation, propagation, and protection. Mechanical analysis of quenching magnets is of high importance considering the design of new protection systems and the study of new superconductor types. We use field/circuit coupling to determine temperature and electromagnetic force evolution during the magnet discharge. These quantities are provided as a load to existing mechanical models. The models are discretized with different meshes and, therefore, we employ a mesh-based interpolation method to exchange coupled quantities. The coupling algorithm is illustrated with a simulation of a mechanical response of a standalone high-field dipole magnet protected with Coupling-Loss Induced Quench Technology.

Numerical Modeling of Dynamic Loss in HTS-Coated Conductors Under Perpendicular Magnetic Fields

Abstract: High-Tc superconducting (HTS)-coated conductors are a promising option for the next-generation power devices. However, their thin-film geometry incurs dynamic loss when exposed to a perpendicular external ac magnetic field, which is difficult to predicate and estimate. In this paper, we propose and verify a numerical simulation model to predict the dynamic loss in HTS-thin-coated conductors by taking into account their Jc-B dependence and I-V characteristics. The model has been tested on a SuperPower YBCO-coated conductor, and we observed a linear increase of dynamic loss along the increasing field amplitude after the threshold field. Our simulation results agree closely with experimental measurements as well as an analytical model. Furthermore, the model can predict the nonlinear increase of dynamic loss at high current, while the analytical model deviates from the measurement results and still shows a linear correlation between the dynamic loss and the external magnetic field. In addition, we have used this model to simulate the distributions of magnetic field and current density when dynamic loss occurs. Results clearly show the flux traversing the coated conductor, which causes dynamic loss. These distributions have also been used to analyze the change of dynamic loss when either the transport current or the magnetic field increase individually, while the other factor remains constant. The simulation analysis on dynamic loss is done for the first time in this paper, and our results clearly demonstrate how dynamic loss changes as well as its dependence on transport current and magnetic field.

Design and Fabrication of a 1-MW High-Temperature Superconductor DC Induction Heater

Abstract: The high-temperature superconductor (HTS) dc induction heater shows great potential in the efficiency increase and heating quality improvement, which has been validated by previous prototypes. Now, Shanghai Jiao Tong University has been developing and fabricating an industrial scale 1-MW HTS dc induction heater in China. The heater is utilized to preheat aluminum billets 446 mm in diameter × 800–1500 mm in length. Two cryocoolers are applied for coil cooling with pluggable sleeve and providing an additional safety margin whose normal operating temperature is 30 K. The magnet consists of a double pancake coils wound by REBa2Cu3O7-δ -coated conductors, which are produced by Shanghai Superconductor Technology Company. More than 12-km HTS tapes are used and the inductance of coil with iron is 98 H. The HTS magnet's critical current is 213 A. The 0.5-T dc magnetic field is set up in the two air gaps of HTS magnet with an iron core. The adjustable iron yoke distribution along the axial direction of billets can meet the 100 °C adjustable temperature gradient design requirement. The results will be helpful to design for the commercialization of the HTS dc induction heater.

Electromechanical Design of a 16-T CCT Twin-Aperture Dipole for FCC

Abstract: Canted-cosine-theta (CCT) technology has been studied for its suitability for a future-circular-collider (FCC) main dipole in terms of magnetic and mechanical performance, electrothermal protectability, as well as efficiency. In this paper, we present lessons learnt from our search for efficient CCT solutions by means of two-dimensional (2-D) magnetic and mechanical simulations, discuss the 3-D periodic mechanical model, as well as 3-D electromagnetic analysis of the end regions. Temperature and voltage distributions during a quench under simplifying assumptions are discussed, and the magnet's efficiency is compared to that of other contenders in the FCC design study. The results qualify the CCT design as a contender for the FCC main dipole.

STEAM: A Hierarchical Cosimulation Framework for Superconducting Accelerator Magnet Circuits

Abstract: Simulating the transient effects occurring in superconducting accelerator magnet circuits requires including the mutual electro-thermo-dynamic interaction among the circuit elements, such as power converters, magnets, and protection systems. Nevertheless, the numerical analysis is traditionally done separately for each element in the circuit, leading to possible inconsistent results. We present STEAM, a hierarchical cosimulation framework featuring the waveform relaxation method. The framework simulates a complex system as a composition of simpler, independent models that exchange information. The convergence of the coupling algorithm ensures the consistency of the solution. The modularity of the framework allows integrating models developed with both proprietary and in-house tools. The framework implements a user-customizable hierarchical algorithm to schedule how models participate to the cosimulation, for the purpose of using computational resources efficiently. As a case study, a quench scenario is cosimulated for the inner triplet circuit for the high luminosity upgrade of the Large Hadron Collider at CERN.

Charging 2G HTS Double Pancake Coils With a Wireless Superconducting DC P ower Supply for Persistent Current Operation

Abstract: We have designed and built a novel high-temperature superconducting (HTS) flux pump device to charge a second-generation (2G) HTS double pancake coil (DPC). This device generates dc-biased ac travelling wave on sections of 2G HTS coated conductor (superconducting stator), which pumps flux into the superconducting closed loop formed by the DPC and superconducting stator. In this paper, we discuss the importance of the dc-biased field, ac travelling wave, and the travelling direction in the flux pump process, and how to control the magnetization of an HTS coil with the above factors. We have found that a pure ac travelling wave can only transport net flux into the superconducting closed loop in the presence of dc-bias field. The magnetization direction of the DPC can be reversed by reversing the dc-bias direction of the dc background field or travelling direction of the ac travelling wave. This paper shows the versatility and flexibility of this novel flux pump device in controlling the magnetization of the HTS coils, which will work as a wireless dc power source to help persistent current mode operation of a small-scale MRI magnet built by HTS DPCs later in this project.

A Finite-Element Method Framework for Modeling Rotating Machines With Superconducting Windings

Abstract: Electrical machines employing superconductors are attractive solutions in a variety of application domains. Numerical models are powerful and necessary tools to optimize their design and predict their performance. The electromagnetic modeling of superconductors by the finite-element method is usually based on a power-law resistivity for their electrical behavior. The implementation of such constitutive law in conventional models of electrical machines is quite problematic: the magnetic vector potential directly gives the electric field and requires using a power-law depending on it. This power-law is a nonbounded function that can generate enormous uneven values in the low electric field regions that can destroy the reliability of solutions. The method proposed here consists in separating the model of an electrical machine in two parts, where the magnetic field is calculated with the most appropriate formulation: the H -formulation in the part containing the superconductors and the A -formulation in the part containing conventional conductors (and possibly permanent magnets). The main goal of this work is to determine and to correctly apply the continuity conditions on the boundary separating the two regions. Depending on the location of such boundary—in the fixed or rotating part of the machine—the conditions that one needs to apply are different. In addition, the application of those conditions requires the use of Lagrange multipliers satisfying the field transforms of the electromagnetic quantities in the two reference systems, the fixed and the rotating one. In this paper, several exemplary cases for the possible configurations are presented. In order to emphasize and capture the essential point of this modeling strategy, the discussed examples are rather simple. Nevertheless, they constitute a solid starting point for modeling more complex and realistic devices.

Design and Analysis of a Hybrid Permanent Magnet Assisted Synchronous Reluctance Motor Considering Magnetic Saliency and PM Usage

Abstract: This paper proposes a new hybrid permanent magnet (PM)-assisted synchronous reluctance motor, where two types of PM materials of rare-earth PMs and ferrite PMs are employed in its rotor. To reduce the usage of rare-earth materials, a hierarchical design method is adopted in its rotor design, in which the design is divided into two levels: saliency ratio design level and PM usage design level. In saliency ratio design level, proper flux barrier dimensions are confirmed based on the principle of reluctance torque maximization. In PM usage design level, the optimal magnet ratio is first determined according to the relationship of main flux and leakage flux. Then, a tradeoff design is conducted to seek the superior combination of low torque ripple, high efficiency, and high power factor. Finally, for the purpose of validation, the electromagnetic performances of the new designed motor are investigated, including torque characteristics and antidemagnetization capabilities of ferrite.

Recent Status and Progress on HTS Cables for AC and DC Power Transmission in Korea

Abstract: The direction of the development of large-scale electric power networks has very much coincided with the history of increasing voltage values ever since the advent of Joule heat loss. However, a high-temperature superconducting (HTS) technology has changed the direction of that history. Furthermore, the HTS technology will rapidly accelerate the speed of such change due to its extremely high current density with no Joule heat loss. For these reasons, many different types of HTS electric power transmission applications have been being discussed, and selected items have been developed. Within a few decades, the technology of HTS ac and dc power transmission applications had already been developed and close to the required level for industrialization. Moreover, some of these applications have been installed, energized, and are operating within real power networks. In this paper, we report on the current status and progress in HTS applications of ac and dc power transmission. In particular, this paper focuses on the application field of superconducting cable among various HTS power applications. In South Korea, the Korea Electric Power Corporation, Naju, aims to introduce more new technologies in order to develop the Korean power network, and it believes that an HTS is a key factor in the development of the next generation of power grid, which will be discussed in detail in this paper.

Design and Experimental Tests of a Superconducting Hybrid DC Circuit Breaker

Abstract: Direct current (DC) circuit breakers are a key enabling technology for fault management in multiterminal high-voltage DC (HVDC) systems DC fault isolation is challenging due to the high rate of rise of the fault current and the lack of natural current zero-crossings found in ac systems In this paper, we present a novel superconducting hybrid dc circuit breaker that utilizes the intrinsic characteristics of the superconductor material The automatic quench of the superconductor coil as a result of a high fault current transfers the current from the mechanical switch to the semiconductor switch The isolating mechanical switch is able therefore to open at low current and recover its dielectric capability rapidly A low voltage DC circuit breaker prototype has been built using a multistrand magnesium diboride (MgB2) coil, a vacuum interrupter, and an insulated-gate bipolar transistor module This prototype successfully demonstrated interruption of 500 A DC within 44 ms This paper presents the design of the superconducting hybrid breaker prototype and a detailed analysis of the experimental results This superconducting hybrid dc circuit breaker has significant potential for scaling up the high-voltage and high-current applications

Study on High Efficiency Permanent Magnet Linear Synchronous Motor for Maglev

Abstract: This paper discusses the traction performance of a single-side linear induction motor and a single-side coreless Halbach permanent magnet linear synchronous motor (PM-LSM) for the mid- and low-speed maglev train Based on a typical mid- and low-speed maglev transit system, the overall performance of the two kinds of propulsion motors was analyzed by the finite element method By comparing the performance of the single-side coreless Halbach PM-LSM at different magnetization direction of the PMs of the Halbach array, the optimal angle between the magnetization direction of two adjacent PMs was found In order to achieve the higher propulsion efficiency of the single-side coreless Halbach PM-LSM, various cross-sectional shapes of the conductor were analyzed The analytical results indicate that the coreless Halbach PM-LSM is more suitable for the mid- and low-speed maglev train in urban rail transit system

Superconducting Magnetic Field Programmable Gate Array

Abstract: Field-programmable gate arrays (FPGAs) provide a significantly cheaper solution for various applications in traditional semiconductor electronics. Single flux quantum (SFQ) technologies are developing rapidly and the availability of SFQ-specific FPGA will be very useful. Towards developing such an SFQ-specific FPGA, new designs of FPGA subcircuits for both synchronous and asynchronous operation of SFQ circuits are presented in this paper. Magnetic Josephson junctions (MJJs) are used as bias limiting junctions in energy-efficient rapid SFQ (ERSFQ) biasing to implement programmable switches in various subcircuits of the proposed FPGA fabric. Designs of all FPGA subcircuits are developed and are verified through circuit simulation. Verilog hardware description language (HDL) models are also developed for all FPGA circuit blocks to facilitate large-scale FPGA simulations for the implementation of the desired circuit on the proposed FPGA fabric. Designs of a few subcircuits with switches based on nondestructive readout cell are also given in the current paper for better comparison with MJJ switch based counterparts. Programming of MJJ-based switches is based on the ability to control the critical current of MJJs externally. Recent implementations of SFQ decoder is proposed for accessing individual MJJs through the current lines in a crossbar structure. Estimations for the area and power consumption are much better in comparison to previous attempts at designing an SFQ specific FPGA.

Properties of Ferromagnetic Josephson Junctions for Memory Applications

Abstract: In this paper, we give a characterization of the RF effect of memory switching on Nb-Al/AlO x -(Nb)-Pd 0.99 Fe 0.01 -Nb Josephson junctions as a function of magnetic field pulse amplitude and duration, alongside with an electrodynamical characterization of such junctions, in comparison with standard Nb-Al/AlO x -Nb tunnel junctions. The use of microwaves to tune the switching parameters of magnetic Josephson junctions is a step in the development of novel addressing schemes aimed at improving the performances of superconducting memories.

Development of ReBCO-CORC Wires With Current Densities of 400–600 A/mm $^2$ at 10 T and 4.2 K

Abstract: Thin ReBCO tapes of 2 mm in width and only 30- $\mu$ m substrate thickness allow production of thin CORC wires of 3–4 mm in diameter. These CORC wires feature high bending flexibility and high current densities as required for high field magnets. Two CORC wires, the first with 50 tapes and the second with 29 tapes, were developed and tested in a common effort of CERN, ACT, and the University of Twente. The two CORC wires were tested as small solenoids in transverse magnetic fields of up to 10.5 T and at 4.2 K. Afterwards, single tapes were extracted from the samples and tested individually in self field at 76 K. The first CORC wire had a critical current of 4255 A and an engineering current density of 322 A/mm $^2$ , while the second wire showed 3970 A and 412 A/mm $^2$ , both at 10 T and 4.2 K. The extracted tape analyses showed points of improvement for both wires, and therefore, provide valuable feedback for improving the wire production process and wire handling. CORC wire optimization resulted in no performance degradation of the 29-tape wire during electromagnetic load cycling at high magnetic fields. In this paper, details are presented on the CORC wires and measurement results are summarized.