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Second-generation high-temperature superconductors, being brittle, need to be deposited on a substrate and converted to tapes with additional reinforcement layers. These tapes are wound on a core to make superconducting wires and cables. The mechanical loads during bending, twisting, winding, etc., can degrade the superconductor. It is necessary to determine the strain-induced during these processes. Variations in induced strain with bending of superconductors have been investigated analytically and numerically for various configurations of Rare-Earth Barium Copper Oxide (REBCO) tape. The numerical simulation has been carried out using COMSOL Multiphysics software; the analytical examination of the effect has been performed applying the Flexure formula. The geometrical configuration of the superconducting tape is varied in terms of the bending radius, the thickness of constituting layers made of Hastelloy and copper. The results showed that the variation in the thickness of the substrate has a large influence on the induced strain. Electrical performance analysis is also carried out using the power law of strain dependence and the 5% critical current degradation point is noted. Results of these numerical and analytical investigations are expected to help in finding out critical parameters to avoid degradation while being in use. [ABSTRACT FROM AUTHOR]

High temperature superconductor (HTS) is becoming more andmore attractive for high fieldmagnets. To charge the HTS magnets and operate them in persistent current mode, a persistent current switch (PCS) is necessary. This paper will focus on how to build a fast persistent current switch which can present a large resistance and with short recovery time. Impacting factors and strategy to control the PCS are discussed. An experimental system is built and tests are carried out to verify the practicality of the proposed PCS. [ABSTRACT FROM AUTHOR]

A high-temperature critical superconductor (HTS) dipole magnet relying on 12-mm REBCO tapes was built at CEA Saclay in 2016. Magnet studies had been started in the framework of the EuCARD High FieldMagnet program and continued within a collaboration agreement between CEA-Saclay and CERN. The final goal is to generate 5.4 T at 4.2 K in the 13-T background field of the FRESCA2 Nb3Sn dipole magnet. The HTS winding is made of three double-layer racetrack-type coils, wound from a stack of two double-layer REBCO tapes, stabilized with beryllium copper ribbons. Before it is installed inside the aperture of FRESCA2, at CERN, themagnet has been tested at CEA-Saclay in the standalone mode. In this paper, after a brief recall of the magnet design, we will report on the magnet manufacturing and the first powering tests results. [ABSTRACT FROM AUTHOR]

Quench detection for the high-temperature superconducting tape, especially rare-earth barium copper oxide (REBCO) tape, is difficult due to the small normal zone propagation velocity in it. To address this issue, we have proposed a novel quench detectable REBCO tape with a low-temperature superconducting wire used as a quench detector, "REBCO/LTSd tape." In this paper, we numerically and experimentally demonstrated the validity of the tape consisting of the yttrium barium copper oxide (YBCO) tape and the Nb-Ti wire used at 4.2 K under no external field. Results of the numerical simulation showed that sufficiently high voltage of 0.1 V can be detected before the maximum temperature of the YBCO tape reaches 50 K with the Nb-Ti wires having high resistance at normal conducting state. Experimental results also demonstrated that the quench in the YBCO was detected with the 1 V scale voltage by using the pure Nb-Ti wire. [ABSTRACT FROM AUTHOR]

We developed a method to combine parallel superconducting HTS tapes to a current carrying element with high current and uniform current distribution among strands at ac mode. The current carrying elements are made of several parallel HTS tapes placed side-by-side on a round mandrel. The test of the small model made of five parallel 2G HTS tapes confirmed the idea. The method was implemented for 10/0.4 kV, 1 MVA power transformer. For both low and high voltage windings, we used 12 mm Amperium tapes from American Superconductor Co. For low-voltage winding 19 parallel tapes were wound on four mandrels and connected in series. High-voltage winding was wound with a single 12 mm tape. The assembled windings of each phase were tested at liquid nitrogen temperature without iron yoke. AC losses were measured in low-voltage winding at two modes: when high voltage winding was either shortened or open. In this paper, we present the details of current carrying element development and test, 1 MVA transformers winding designs and test results. [ABSTRACT FROM PUBLISHER]

It is believed that the size of wind turbines on offshore wind farms can be increased up to 10 MW. A superconducting synchronous generator (SCSG) is advantageous to a large-scale wind turbine because of its weight and volume. In this paper, a grid-connected large-scale superconducting wind turbine generator is analysed under varying wind speeds. A 10 MW SCSG is designed by the finite elements method (FEM). The parameters of the designed SCSG are calculated and applied to a modeled SCSG in a Power System Computer Aided Design/Electromagnetic Transients including DC. The electric and dynamic performances of superconducting wind turbine generators are analysed in this simulation. This paper shows the effectiveness of the grid-connected superconducting wind turbine generator for offshore applications. [ABSTRACT FROM PUBLISHER]

This paper presents the quench detection method with using normal transition behavior for HTS coil. If the HTS coil starts to propagate a normal zone by an initial quench, it will be recovered the superconducting state or runaway thermally. These behaviors were mainly determined by variety parameters like the magnitude of a disturbance, HTS coil size, the structure of winding wire and cooling condition. However, the first step of detection or protection for coils should be started from detecting the presence of a non-recovering normal zone. This paper classifies the initial quench behaviors of HTS wires or coils as a model of 3-type tendencies, and suggests suitable detection techniques for each tendency with using the end-to-end voltage of coil. In additional, this method is able to detect a quench without a decisive criterion used at other quench detection methods. In order to confirm the validity of the method, we used the HTS sample coil wound with YBCO tapes. This paper presents these results and the quench protection properties with fabricated detection method. [ABSTRACT FROM AUTHOR]

It is well known that high temperature superconductors (HTS) are promising for a magnet application, but it has been almost impossible so far to apply them to the magnet in persistent current mode because of poor qualities of their superconducting joint at higher current as well as lower index values. In this paper, in order to get rid of the joints from an HTS superconducting magnet, a prototype HTS pancake coil using YBCO coated conductors by the technique of wind-and-flip pancake coil was made and will be tested later. This paper presents a design, fabrication, and thermal analysis of the prototype pancake coil. The coil will be cooled down around 20 K by conduction cooling using a GM cryocooler. The expected current drift rate for an MRI application has not been achieved, probably caused by large flux flow resistance of coated conductor at higher temperature, 77.3 K. A temperature dependency of temporal stability of the persistent current will be measured by monitoring the long-term drift of the magnetic field at different operating temperatures by Hall sensors. [ABSTRACT FROM AUTHOR]

This paper explains novel methods of the excessive current protection for a single unit 25-kA current injection system (CIS) with no test interruption. The principle object of this paper is to provide a fast detection of excessive current in the system by means of an unbalanced magnetic flux current limiting device (CLD) for the predetermined current tests. The proposed techniques will be used to investigate the performances of different CLD core structures. The paper will also push the state of the art by applying magnetic fields to the high-temperature superconductor element through an external source, to get higher resistance in the current-limiting phase. A further object of this investigation is to provide the use of open-core in two different mechanisms for limitation and protection purposes of the CIS. This can be considered as a viable alternative CLD for applications in the power industry. This will result in a more thorough knowledge of "scaling factors" and the excessive current limitation mechanism which will enable the most efficient limitation in terms of compactness and cost to be specified. Completion of this development will mark an important milestone in superconductor technology, and significant efficiency improvement will be realized. [ABSTRACT FROM AUTHOR]

This paper deals with feasibility of fault current limiter (FCL) by using Bi-2223 high temperature superconducting (HTS) wire. The FCL using HTS wire has some advantages of stability, flexibility of structure and cost compared with existing superconducting FCLs using bulk or thin film. Even if the FCL using HTS wire has zero resistance in normal state, it needs to be wound as a bifilar winding for non inductance. In this paper, four types of FCL module with bifilar winding were suggested, manufactured and experimented with short circuit tests in 77 K. The FCL modules have different fault current limiting characteristic and stability respectively. These types of module are solenoid, pancake, solenoid impregnated with epoxy resin and pancake impregnated with epoxy resin. The FCL module was applied by controllable AC bias during fault duration, 0.1 s, from 0.5 V to 22 V. A process of fault occurrence in this test is very similar to a fault occurrence in real system. In results of tests, the pancake type was more effective to limit a fault current than the solenoid type. Also modules impregnated with epoxy resin showed more efficient current limiting characteristics than nonimpregnated modules. The solenoid type has better characteristic of stability. The feasibility of the FCL by using HTS wire was verified by this paper. [ABSTRACT FROM AUTHOR]

This paper presents a novel configuration of a beam- forming 16-port Butler matrix centered on a frequency of 2 GHz. The structure is implemented using high-temperature superconductors (HTS). In communication and remote sensing systems, multibeam antenna systems are gradually replacing single-beam systems. Microwave beamformer circuits for these applications require a large number of couplers and phase shifters, which result in a large circuit size. By using microstrip structures on high permittivity substrates, the circuits can be miniaturized. However, the insertion loss of the beamformer increases due to the conductor loss. The use of HTS allows reduction in the size of the circuit while maintaining low insertion loss, due to the low conductor loss compared to conventional conductors. The Butler matrix described here uses a two-layer configuration, which removes any microstrip line crossovers; it can be constructed by traditional photolithographic methods. In this paper, the design of the matrix is discussed, together with the experimental and simulated results. [ABSTRACT FROM AUTHOR]

The new energy revolution which will be dominated by renewable energy will need to develop a corresponding new power grid. Based on the characteristics of renewable energy resources, and the stability problem of AC network, it was proposed that the DC-based transmission grid should be developed in the future. The high Tc Superconducting (HTS) power cable will be a competitive candidate for large-capacity power transmission of renewable energy. In this paper, the progress of the development of a 360 m/10 kA HTS DC power cable is presented, and the prospects of HTS cable is discussed. [ABSTRACT FROM PUBLISHER]

With the increasing depletion of fossil fuels and growing environmental pressure, the mankind has got known the need to vigorously develop the renewable energy and the energy-saving technology. The high Tc superconducting (HTS) power technology will be very helpful to enhance the stability, reliability, and efficiency and transmission capacity of the power grid which would be dominated by the renewable energy. In this paper, we will report the installation and operation of a 10 kV HTS power substation which includes a 75 m/1.5 kA HTS power cable, a 10 kV/1.5 kA HTS fault current limiter, a 1 MJ/0.5 MVA high Tc SMES and a 630 kVA/10 kV/0.4 kV HTS power transformer. [ABSTRACT FROM PUBLISHER]

The amount of hysteresis losses is a key parameter for the design of high-temperature superconducting (HTS) transformers. Leakage field, particularly its radial component, decreases critical current and increases hysteresis losses in HTS tapes. Prior art proposed the adoption of two auxiliary windings to an HTS transformer for minimizing the leakage flux densities by generating a field that opposes the leakage field, thereby reducing the hysteresis loss in an exemplary HTS transformer. In this paper, a proposed design will become prominent by obtaining a variant of distributive ratios via an intelligent choice of the secondary–primary–secondary–primary turn ratios in the neighborhood of the auxiliary windings to produce magnetic poles canceling or diminishing the corresponding leakage fields to the maximum effect. The mentioned schemes require accurate, yet efficient, advanced numerical techniques using 3-D solver of FLUX software for a precise calculation of the leakage flux density and hysteresis losses in an exemplary HTS transformer as a precious guide. [ABSTRACT FROM AUTHOR]

A double-shell rectangular-shape liquid nitrogen vessel with thin wall for high temperature superconductor (HTS) Maglev vehicle is described in this paper. Its severe working conditions, such as sharp low temperature and strong magnetic field, determine its special structure. Three dimensional finite element analysis (FEA) using dimensions of the vessel, especially thickness of the walls, the largest levitation force obtained from the former experimental results, properties of metallic and nonmetallic material as design parameters was conducted to obtain optimal structure of the vessel. FEA of austenitic stainless steel 0Cr18Ni9Ti metallic vessel and polymer composite (PC) nonmetallic vessel with thin wall were performed. Comparison of the calculation results of two kinds of vessel shows that PC nonmetallic vessel can well satisfy the requirements of HTS Maglev vehicle. Furthermore, PC nonmetallic vessel has many advantages such as no eddy current loss, lesser total weight and lower cost, etc. Due to the finite element model (FEM) being simplified, the results of the numerical calculation should be verified by experimental results. Whereas, FEA as a powerful tool to predict stress and deformation of the model, it can guide and optimize the design of the liquid nitrogen vessel effectively. [ABSTRACT FROM AUTHOR]

The termination of an HTS cable is done in liquid nitrogen and air, it has to endure thermal contraction in addition to providing electrical insulation. Therefore, such a termination should not only keep the potential gradient at the front side of the insulation uniform but should also be completely sealed from the atmosphere and should provide thermal stability under worst case operating conditions. In this paper, the insulation properties of termination were investigated. Based on these experimental data, the electrical insulation design of termination for a 22.9 kV class HTS cable was performed. [ABSTRACT FROM AUTHOR]

This paper describes the NMR/MRI magnets that are currently being developed at the MIT Francis Bitter Magnet Laboratory: 1) a 1.3 GHz NMR magnet; 2) a compact NMR magnet assembled from YBCO annuli; and 3) a persistent-mode, fully-protected MgB2 0.5-T/800-mm whole-body MRI magnet. [ABSTRACT FROM AUTHOR]

The superconductor-triggered type fault current limiter (STFCL), which was developed by Korea Electric Power Corporation (KEPCO) and LS Industrial Systems (LSIS), is under operation for the verification test at KEPCO's power testing center. The STFCL is composed of superconductor, fast switch and current limiting resistor. The fault current is suppressed after a half cycle by the method of a line commutation. In this paper, we investigated the empirical modeling of STFCL using principal components and auto-associative support vector regression (PCSVR) for the prediction and fault detection of the STFCL. Signals for the model are currents and voltages acquired from high-temperature superconductor (HTS), driving coil (DC) and current limiting resistor (CLR). After developing the empirical model we analyse the accuracy of the model. The results were compared with that of auto-associative neural networks (AANN). PCSVR showed much better performance in accuracy aspect. Moreover, this model can be used for the prognosis of STFCL system. [ABSTRACT FROM AUTHOR]

This paper presents a mechanical tuning method for tuning the center frequency of a narrowband high-temperature superconducting filter. The filter is designed with 0.5-MHz bandwidth at 166.9 MHz and is fabricated. Tuning is carried out based on the time-domain response of filter return loss. The filter can be precisely tuned to a desired center frequency while maintaining a high-frequency performance. The center frequency is tuned from 167.2 to 166.5 MHz. The tuning range is 0.7 MHz and is sufficient to compensate the frequency offset caused by 0.72% variation in the substrate effective dielectric constant or 4% that of the substrate thickness. [ABSTRACT FROM AUTHOR]

Application of the second generation High Temperature Superconducting (HTS) YBCO tapes has been increasingly popular since the low-cost superconducting materials were discovered. This paper mainly presents the properties of two types of 2G YBCO tapes from American Superconductor Corporation (AMSC) and SuperPower, Inc, respectively. All superconducting materials are cooled by liquid nitrogen (77 K). At first, we will introduce the basic design strategy for synchronous motor and characteristics of superconducting materials. Then, the basic principle and algorithm for calculation and measurement of Ic and AC transport loss will be explained. Secondly, the novel measurement system using a high-precision digital lock-in amplifier is presented. Finally, we present and analyze simulation and experimental results for two types of YBCO tapes in bending condition. [ABSTRACT FROM AUTHOR]

A 35 kJ/7 kW conduction-cooled HTS SMES is developed. The magnet of the SMES is a solenoid type coil, made of Bi2223/Ag tapes, and cooled to about 20K by a cryocooler through conduction-cooled method. To evaluate the performance of the 35 kJ/7 kW SMES, system characteristics such as current carrying ability, power conditioning capability and dynamic operation for stabilizing power systems are investigated by experiments. In this paper, the temperature characteristic of the conduction-cooled HTS magnet for 35 kJ/7 kW SMES is analyzed. Experimental results verify that the thermal stability of the HTS magnet can meet the requirement of dynamic power compensation. Integrating with the analysis of the energy loss in dynamic operation of the magnet, the methods to reduce the energy loss and improve the thermal stability of the conduction-cooled HTS SMES magnet are discussed. [ABSTRACT FROM AUTHOR]

HTS pancake windings have been commonly used for the insert coil of high field magnets. All pancake windings have been connected in series and excited by a single power source. In that case, currents of the whole pancake windings were limited by the minimum current of the top and the bottom pancake windings where maximum perpendicular magnetic field was applied. This paper proposed the multiple power excitation of the HTS magnet which consists of pancake windings. It was able to increase the magnetic field of the magnet by conducting critical currents to all pancake windings. Results of calculation by using a model BSCCO magnet shows that proposed method was able to generate higher magnetic field comparing with the conventional single power excitation. [ABSTRACT FROM AUTHOR]

When the HTS magnet consisting of pancake windings is excited by a single power source, most of the pancake windings operate under their critical currents because currents of the entire pancake windings are limited by the critical current of the pancake winding which has the lowest critical current. By using multiple power sources, all pancake windings are able to conduct their critical currents. This paper describes the HTS magnet with pancake windings which are excited by multiple power sources. Critical current of each pancake winding is determined by using optimization technique. Fabrication of the BSCCO magnet consisting of 10 pancake windings is described and test results of the BSCCO magnet are given. The magnetic field and the perpendicular magnetic field of the magnet excited by multiple power sources are compared with those of the magnet excited by a single power source. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the electrodynamical properties of YBa2Cu3O7-x strip-shaped films, which were locally modified by confined heavy-ion irradiation. The irradiations were made by means of 4.2 GeV gold ions. Quantitative magneto-optical imaging as well as in-field transport characterizations show how the irradiated regions locally react to an external electromagnetic perturbation, thus allowing its localization and measurement. Aiming at future applications, the main issues about the detector sensitivity, such as the role of interfaces between irradiated and pristine regions, are addressed. [ABSTRACT FROM AUTHOR]

Development of the Second Generation (2G) YBCO High Temperature Superconducting wire has progressed rapidly and its performance is approaching, and in some areas exceeding, that of First Generation (1G) HTS wire. American Superconductor's approach to the low-cost manufacturing of 2G wire is based on a wide-strip (4 cm) process using a Metal Organic Deposition (MOD) process for the YBCO layer and the RABiTS (Rolling Assisted Biaxially Textured Substrate) process for the template. In addition, the wide-strip RABiTS/MOD-YBCO process provides the flexibility to engineer practical 2G HTS wires with architectures and properties tailored for specific applications and operating conditions through slitting to custom widths and laminating with custom metallic stabilizers. This paper will review the status of the 2G manufacturing scale up at AMSC and describe the properties and architecture of the 2G wire being developed and tested for various applications including in cables, coils and fault current limiters. Performance of 100 meter class, 4 mm wide wires at 77 K, self-field has reached 100 A (250 A/cm-width) with single-coat YBCO and 140 A (350 A/cm-width) with double-coat YBCO. A 5 cm inner diameter coil fabricated from the latter wire achieved 1.5 T at 64 K, confirming the capability of the wire for coil applications. [ABSTRACT FROM AUTHOR]

Since 2003, three years of the current 5-year national project for development of coated conductors using Y-system superconductors have passed and remarkable results have been achieved. In this paper, the current status and future prospects are reviewed. The group of Fujikura and SRL has worked on a long tape with high performance in the PLD-YBCO supercon- ducting tapes on the IBAD-GZO buffered substrates. The highest Ic × L value of the tape is over 50 k Am which is 212 m in length and 245 A of critical current (Ic). Additionally, a 500 m long IBAD-buffered tape with a reasonable in-plane texture was produced using a large scale IBAD apparatus by Fujikura. In the other group, long tape processing has been developed focusing on lowering production cost. An extremely high Ic value of 692 A was obtained in a short sample by the advanced TFA-MOD method on a CeO2 (PLD)/GZO(IBAD)/Hastelloy substrate. In the efforts for the long tape processing, a 25 m long tape with the Ic value of 100 A by a continuous reel-to-reel system and a 40 m long tape with 155 A by a batch system were realized. 100 m class long tapes were also obtained with the MOCVD and PLD-HoBCO processes. Both groups are aiming for 500 m long tapes with the high Ic value of 300 A/cm-w with a production rate of 5 m/h. Furthermore, feasibility studies for applications using coated conductors have already began due to the above mentioned success of long tape production. Several kinds of coils using the long coated conductors such as solenoid and pancake types and spiral shaped conductors for the cable were made. Reasonable high performance results were confirmed in the trials. New approaches on the preliminary studies for the applications of cables, transformers, motors and current limiters etc. are planned in this project. [ABSTRACT FROM AUTHOR]

In this paper we present a new 2D numerical model for AC loss computation in high-temperature superconductors, based on the use of edge finite elements. These elements are curl conforming by construction and involve the continuity of the tangential component of the magnetic field between adjacent elements. In this way they do not require the imposition of the zero divergence of the magnetic field at each time step, which, with standard nodal elements, increases the null space of the matrix and the risks of divergence of the algorithm. The model, implemented in the software package COMSOL, uses the two magnetic field components as state variables. It has been tested for computing the losses of YBCO coated conductor tapes in two cases of practical interest, which cannot be investigated by analytical models. [ABSTRACT FROM AUTHOR]

According to the recent design of an HTS (High Temperature superconducting) power application whose capacity is hundreds MVA, the rated current is over thousand amps. Considering the performance of the recent HTS tapes, it is inevitable to use several HTS tapes in parallel for high capacity current. In this paper, we have investigated the influence of current distribution on the AC loss in the multi-stacked superconducting wire. The dependence of AC loss and critical current on the current distribution in multi-stacked wires was discussed. We fabricated multi-stacked wires and measured the current distribution at 77 K. The current distribution was indirectly found from the self-field distribution. The magnetic field was measured by an array of hall sensors located around the HTS superconducting wires. In the case of non-uniform distribution of current, the performance of multi-stacked HTS wires is worse than that of uniform current distribution. [ABSTRACT FROM AUTHOR]

A 600 kJ Superconducting Magnetic Energy Storage System (SMES) project with High Temperature Superconductor (HTS) started as a national project in Korea. The HTS model coils were designed and fabricated for a preliminary test prior to the creation of a full scale prototype. Single reinforced BSCCO-2223 wires were used for the model coils and the operating temperature was decided to be 20K. Even though an SMES is not an AC-powered device, time-varying currents during the charging and discharging periods lead to the generation of time-variation magnetic fields applied to the model coils and the generation of AC loss. In this paper, AC loss and the temperature distribution of model coils are analyzed and discussed. [ABSTRACT FROM AUTHOR]

In conduction-cooled HTS magnets, it is important to design effective heat drains from the HTS tapes to a cold head of a refrigerator. Aluminum nitride (AlN) is often used as a heat-drain material because thermal conductivity and electric insulation of the material are good. However, the AlN is hard and brittle, and hence it is difficult for magnet makers and users to process the AlN. To address this issue, we have studied to use the plastic having both high-thermal conduction and high-electric insulation properties as the heat drain material. The plastic is the Dyneema fiber reinforced plastic (DFRP). We fabricated an experimental arrangement in which the Bi-2223 tape and the DFRP block were contacted, and a steady current was applied to the tape. Based on the measured voltage between terminals, thermal drain properties from the tape to the DFRP block were estimated. In the same conditions, experiments using the glass fiber reinforced plastic (GFRP) were also performed. Furthermore, the coil shape sample made of the AlN and DFRP were used. The paper presents the difference of the thermal drain performance in the AlN, the DFRP and the GFRP. [ABSTRACT FROM AUTHOR]

Residual magnetic field in a high temperature superconductor (HTS) magnet is a factor which should be avoided when the field of the magnet is being operated under a high uniformity and high accurate control. In this paper, the residual field in a Bi2223/Ag pancake magnet at 77 K is systematically studied. The amplitude of the residual field as a function of maximum charging current and the relaxation of the residual field are measured. For a magnet with an inner diameter of 60 mm, an outer diameter of 80 mm and a height of 30 mm, the maximum residual field is about 14.5 G after ramping the charging current up to 15 A, followed by dropping the current to zero. A simple model is proposed, from which the residual field can be estimated as along as the configurations of the magnet and the critical current (Ic) of the original short sample are given. [ABSTRACT FROM AUTHOR]

HTS based leads have established themselves for high current carrying applications. This work revisits the issues for commercial magnets with a view to minimizing heat load and space for both the resistive and HTS parts. The paper describes the experimental work carried out to develop up to 300 A HTS current leads for Oxford Instruments' Cryofree and liquid helium cooled magnets. The current-voltage, temperature, and quench measurements are reported. The leads make use of BSCCO-2223 HTS wire and have been characterized at 4.2 K, 77 K, and some intermediate temperatures for quench purposes to test their robustness. The leads are in thermal equilibrium with their environment and require no additional cooling, unlike in the case of large current leads for accelerator magnets. The current work on the combined resistive and HTS parts has achieved a boil-off of 20 ml/hr in a liquid cooled cryostat. [ABSTRACT FROM AUTHOR]

Using a high temperature superconductor, we proposed a model Superconducting Fault Current Limiter (SCFCL) with the high-speed commutation switch. The high-speed commutation switch consists of the parallel coil, the electromagnetic repulsion plate and the vacuum interrupter. In this SCFCL, the current in the superconductor is interrupted within 0.5 cycles. By using this equipment, the current flow time in the superconductor can be easily minimized. We studied resistive type SCFCL with the high-speed commutation switch and use YBCO thin film. For applying to high voltage, it is a problem that the superconductors in series connection don't quench immediately for the Ic variations of the various superconductors. In this paper, we conducted the series connection test using YBCO thin films without a metal layer. The research is aimed at the scalability of small models towards commercial size Fault Current Limiter (FCL). [ABSTRACT FROM AUTHOR]

Development of the SMES using high temperature superconducting (HTS) coil has progressed as a Japanese national project since FY 2004. The objective of the project is to obtain around twice the normal energy density via an HTS-LTS ‘hybrid’ coil system compared to an LTS coil system. The HTS coil is composed of sixteen double-pancake coils and the double-pancake coil is wound with a Bi2212 Rutherford-type cable. The HTS coil is operated at 4.2 K in liquid helium bath with the LTS coil, and operated at maximum field of 8.9 T. Before we made a hybrid coil system, we verified the design issues using HTS experimental coils. In this paper mechanical compression tests, DC operation tests and thermal runaway tests using the experimental coils are discussed. [ABSTRACT FROM AUTHOR]

Auto Tuning Niching Genetic Algorithm was used to design optimal HTS magnets for the 600 kJ class SMES system under several design constraint conditions. Constraint conditions were operation loss of magnet (less than 2 W), inductance of magnet (less than 24 H), the number of Double Pancake Coils (about 10 DPCs), the number of turns of DPC (less than 300 turns), outer diameter of DPC (close to 800 mm) and total length of HTS wire in a DPC (less than 500 m). As a result of optimum design, we obtained design parameters for the 600 kJ SMES magnet according to two operating currents, 360 A and 370 A. However, even though the HTS magnet was designed optimally in respect to the electromagnetics, consideration of mechanical integrity due to the stress by Lorentz force must not be neglected for the stable operation of the SMES system. Therefore, we developed a program, through the Finite Element Method (FEM), for stress analysis due to Lorentz force in operation of the SMES system. In this paper, the stresses (radial and hoop stress) imposed on the designed HTS magnets were calculated by the program, and the results of stress analysis were discussed. [ABSTRACT FROM AUTHOR]

In this paper, we report the results from evaluation on the use of 2nd generation high-temperature superconducting wires, or 2G HTS conductors, as elements for superconducting fault current limiter (SFCL). The unique features of 2G HTS conductors such as high N-values, superior electromechanical performance, large surface area available for cooling, and their availability in long-lengths that could be produced by high-throughput and low-cost manufacturing, may provide advantages for SFCL applications. We tested SuperPower's standard ion-beam-assisted-deposition based 2G HTS conductors under various conditions. First, individual conductors 10–20 cm long with dc critical current (Ic) ranging from 180 amps to 277 amps were tested at prospective fault current up to 3 kA (peak). 2G HTS conductors demonstrated good fault current limiting performance, including first peak limitation. Quench current was in the range of 1.8 to 3 times Ic, and the response time was within 1 ms. Secondly, 3–5 conductors in parallel connections demonstrated uniform current sharing and fast recovery under no-load condition. Finally, an assembly consisted of 12 elements in series connection was tested at high-power condition at KEMA PowerTest. Each element had four 40 cm long conductors with Ic ∼120 A in parallel connection. With 1080 V supply voltage and 90 kA prospective fault peak current, the fault current was limited to 32 kA at the 1st peak with 3.2 kA in the HTS elements. The response time was less than 1 ms. All these testing results indicate that our 2G HTS conductors are promising for practical SFCL applications. [ABSTRACT FROM AUTHOR]

This paper deals with the cooling of the rotor of a superconducting motor. We consider three cooling systems: a cold insert, circulation of a cool gas and boiling of a cool liquid. For each case, we study the use of three different gases: hydrogen, helium, neon, and two liquids: hydrogen and neon. For each case of cooling, we define the best gases in term of cooling efficiency. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) coils are generally stable against transient thermal disturbances. Protection against spontaneous quenches is not a main design issue for an HTS coil. However, HTS coils used in many electric devices such as motors, generators, transformers, and current limiters will operate under over-current fault conditions, which may result in a coil quench and thermal runaway. Those electric devices should be able to ride through some grid fault conditions and remain functional. This requires a certain over-current capability of the HTS coils. This paper discusses the over-current requirements from grid faults and the thermal transient responses of a BSCCO coil. It presents the analysis results of the coil subjected to over-current pulses at different operating conditions. The study also investigates the thermal runaway current and its relationship with the over-current pulse. [ABSTRACT FROM AUTHOR]

In this paper, the effect of fabrication conditions on the microstructure and transport Jc properties of thin Y123 fibers were investigated. Fibers with 0.5 mm in diameter were directionally solidified by a zone melting method. The continuous growth structure was achieved in the samples grown at high pulling rates up to 10 mm/h, and the size of trapped Y211 particles was decreased with increasing puffing rate. The transport Jc, values were maximum in the sample pulled at 6 mm/h, and the best Ic and corresponding Jc values achieved were 134 A and 1 × 105 A/cm² at 77 K self-field, respectively. Since the a b-plane of the Y123 crystal is reported to align parallel with the longitudinal direction of the sample grown at high pulling rate, this high Jc value was associated with this preferential crystal orientation as well as fine Y211 particles. Further increase of the pulling rate, however, resulted in the degradation of the crystallinity of the Y123, and the Jc values were decreased. The suppression of the formation of sub-domain structure and the preservation of better crystal orientation are therefore required to attain a high Jc value. [ABSTRACT FROM AUTHOR]

High Temperature Superconductor (HTS) SuperVAR dynamic synchronous condensers (DSC) developed by American Superconductor have a small foot print, are readily transportable, and are expected to be an economic option for providing peak and dynamic reactive compensation to a power system. HTS DSC machines are also inherently stable to close in faults and can provide up to twice their nominal rating for about one minute (peak rating) during depressed voltage events. Last, but not least, HTS DSC machines use less than half of the energy of a conventional synchronous condenser and about the same amount of energy as a modern flexible AC Transmission System (FACTS) device consumes. It is expected to be highly reliable. The first FITS DSC machine is being operated at an arc furnace where it is being tested for its ability to mitigate flicker and provide dynamic power factor compensation. This location also exposes the machine to a large number of transients providing an excellent accelerated age test of the device. This paper describes features and test results of the HTS DSC. [ABSTRACT FROM AUTHOR]

The 500 m high temperature superconducting cable (HTS cable) is 77 kV 1 kA single-core cable with LN2-impregnated paper insulation. Demonstration and verification test of 500 m HTS cable has been started from March 2004 and many useful results can be obtained in the test for future practical uses. Furukawa Electric has mainly taken charge of designing, manufacturing and installation of the 500 m cable. In the manufacturing process, the cable could be fabricated without Ic degradation in Ag/Bi-2223 tapes. Moreover, various factory tests were carried out for the 500 m cable. The result of tests showed that the cable has sufficiently satisfied the quality requirement. In the installation, the cable was successfully pulled into a cable duct of 170 m long like actual underground cable installations. [ABSTRACT FROM AUTHOR]

Efficiency at full toad and starting torque at starting are basic performance criteria of the induction motor. Conventionally deep bar or double cage bar have been used to increase the efficiency and starting torque of the induction motor. Effective resistance of the deep bar and double cage differs from starting to full load operation. To increase the efficiency and starting torque, HTS tapes can be used as the rotor bars. The resistance of HTS tapes develops at starting because of large starting current which exceeds the critical current of the HTS tape and it vanishes as the speed builds up. This paper presents the construction and test results of a HTS induction motor. End rings and short bars were made of HTS tapes. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity of the conventional motor was 0.75 kW. Performances of the HTS induction motor were compared with those of the conventional motor with same volume and specification. Test result showed that the speeds of the HTS induction motor were the same with synchronous speed up to 2.6 Nm and 1788 rpm at 9.7 Nm. It guarantees the high efficiency of the HTS motor. Starting torque of the HTS motor was more than twice of the conventional motor. [ABSTRACT FROM AUTHOR]

The 4-probe method with a voltage tap on terminals has been used for the measurement of the critical current of multi-strand high-Tc superconducting (HTS) cables. The critical current of cables is obtained as the measured total current divided by the number of conductors when the terminal voltage exceeds the predetermined criterion of critical current. However, because of the nonuniform current share due to the different critical currents, shapes, and other characteristics of each conductor, this method is not applicable to the multi-strand HTS cable. To determine the critical current of multi-strand HTS cable, the critical current of each conductor must be measured with different method. In this paper, the current share and the critical current of each conductor in multi-strand cable were measured with specially made pick-up coils and voltage taps. It is presented that the real critical current of multi-strand is smaller than sum of each critical current of each path. Different resistances appeared in each HTS wire are the main cause of nonuniform current share. [ABSTRACT FROM AUTHOR]

Reducing AC losses, cable size and cost of HTS tapes are required for the practical application of HTS power transmission line. We have theoretically investigated the relationship between AC losses and cable parameters such as layer radius and twisting pitch and direction in coaxial multi-layer HTS cable using our developed simulation method and revealed that the larger number of HTS tapes and twisting pitch are desirable for reduction of AC losses. In this paper we investigated influence of twisting pitch and direction on cable size and total amount of HTS tapes under a condition of constant AC losses. The diameter of each layer and total amount of HTS tapes in the cable with the same twisting direction are much smaller than those of alternate twisting direction. The cable with the same tape current would be better than that of the same layer current because of the smaller difference of the number of tapes per layer. In the cable with the same tape current, cable size decreases with the number of layers in spite of almost the same amount of total HTS tapes in the whole cable. In cable design, we cannot handle the restrictions of AC loss and load factor individually; it would be difficult to satisfy both the conditions of low AC loss and high load factor. AC losses could be reduced by increasing critical current of HTS tape without the restriction of load factor, while AC losses increases with the critical current with the restriction of load factor. [ABSTRACT FROM AUTHOR]

The possibility of superferric accelerator and beam line magnets is described. A cooling system that is not helium and nitrogen based, but one based on hydrogen, is proposed to make full use of the recent Mg2 superconductor around 20 K. A hydrogen cooling system is more effective than the nitrogen cooling for usual high Tc superconductors around 70 K. Liquid hydrogen is also excellent as refrigerant for high Tc superconducting apparatus to in crease the critical current and to provide a self-sustained cooling system by means of a combination of evaporated hydrogen and a fuel cell. This paper also discusses hydrogen safety issues, as compared to that of helium and nitrogen. It is expected that dipole magnets for a synchrotron would be good candidates for a super- ferric design based on these principles. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the influence of the super- conducting quantum interference device (SQUID) gradiometer baseline on the recording of magnetocardiographic measurements. The magnetometers consist of high-emperature superconducting radio-frequency SQUIDs fabricated from YBaCuO thin films, and a substrate resonator which serves as tank circuit. The gradiometers are formed using two or three such magnetometers with individual readouts in electronic difference. We have compared the measurement results using a magnetometer and first- and second-order gradiometers with different baselines. In a standard magnetically shielded room, we found not only an increasing signal-to-noise ratio in adult magnetocardiographic measurements, but also a decreasing distortion of the magnetic field map with increasing baseline of the gradiometer. Using a first-order gradiometer with an ultralong baseline of 18 cm, we have successfully measured the heart signal of a fetus in real time. [ABSTRACT FROM AUTHOR]

In order to produce more stable and processable forms of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductors, a series of cation substitution reactions have been completed. Compounds in the family of Y/sub 1-y/Ca/sub y/Ba/sub 1-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// display an increased corrosion resistance with increasing substitution level. The composition of Y/sub 0.6/Ca/sub 0.4/Ba/sub 1.6/La/sub 0.4/Cu/sub 3/O/sub 6.96/-(T/sub c/=80 K) is found to be at least 100 times more stable than the parent compound, YBa/sub 2/Cu/sub 3/O/sub 6.94/. In this paper, compositions yielding transition temperature above 83-85 K have been identified in YBa/sub 2-x/Sr/sub x/Cu/sub 3/O/sub 7-/spl delta// and Gd/sub 1-x/Ca/sub x/Ba/sub 2-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// systems suggesting that the surface reactivity, processability and superconducting properties can be tailored with the use of the appropriate cation compositions. Rational approaches for the systematic tailoring of high-T/sub c/ superconductors based on lattice engineering approaches are thus developed. [ABSTRACT FROM PUBLISHER]

Technologically, the most advanced conductor utilising high temperature superconductors is the multifilamentary tape produced by the powder in tube method. Previous investigations have indicated that the filaments in these materials are strongly connected by superconducting paths. This connectivity is of particular importance in, amongst other things, governing the dissipation of the conductors when carrying AC currents or exposed to varying magnetic fields. In this paper we report direct measurements of the transverse (in contrast to the more usual longitudinal) current carrying capability. Measurements of electric field versus current ('E-I characteristics') for transverse and longitudinal transport currents as a function of applied magnetic field and temperature are reported. Our data indicates that the filaments are indeed strongly connected by superconducting paths but also that the E-I characteristics for the transverse and longitudinal connections are different. [ABSTRACT FROM PUBLISHER]

This paper discusses the results of Booz/spl middot/Allen and Hamilton's investigation of the market acceptance issues which would influence the adoption of high temperature superconducting (HTS) receiver coils for low-field MRI equipment. While HTS receivers could bring distinct advantages in image quality or imaging time, the changing healthcare marketplace, especially for high-end diagnostic imaging equipment, makes adoption problematic. In order to achieve commercial acceptance, HTS coils would have to enable new capabilities or applications, while not violating the marketplace requirements of ease of use, safety, and high reliability. [ABSTRACT FROM PUBLISHER]

This paper describes the design, construction and operation of hybrid dye/superconductor optical sensors. A reflective mirror layer positioned between the dye and superconductor components is used as a means to reject light signals that are not absorbed strongly by the dye. On resonance signals are shown to couple effectively with the underlying superconductor where they evoke measurable responses. These structures form the basis for color selective optical sensors. [ABSTRACT FROM PUBLISHER]