Showing papers in "Physica C-superconductivity and Its Applications in 2013"
TL;DR: The use of the FCL as a mean to allow more interconnection of MV bus-bars as well an increased immunity with respect to the voltage disturbances induced by critical customer is discussed and the possibility to integrate more distributed generation in the distribution grid is also considered.
Abstract: Modern electric power systems are becoming more and more complex in order to meet new needs. Nowadays a high power quality is mandatory and there is the need to integrate increasing amounts of on-site generation. All this translates in more sophisticated electric network with intrinsically high short circuit rate. This network is vulnerable in case of fault and special protection apparatus and procedures needs to be developed in order to avoid costly or even irreversible damage. A superconducting fault current limiter (SFCL) is a device with a negligible impedance in normal operating conditions that reliably switches to a high impedance state in case of extra-current. Such a device is able to increase the short circuit power of an electric network and to contemporarily eliminate the hazard during the fault. It can be regarded as a key component for future electric power systems. In this paper the state of the art of superconducting fault current limiters mature for applications is briefly resumed and the potential impact of this device on the paradigm of design and operation of power systems is analyzed. In particular the use of the FCL as a mean to allow more interconnection of MV bus-bars as well an increased immunity with respect to the voltage disturbances induced by critical customer is discussed. The possibility to integrate more distributed generation in the distribution grid is also considered.
118 citations
TL;DR: In this paper, the authors examined mobile compact YBCO bulk magnet platforms cooled with LN 2 and Stirling cryo-cooler for demonstrator use for Maglev train operation.
Abstract: ATZ Company has constructed about 130 HTS magnet systems using high-Tc bulk magnets. A key feature in scaling-up is the fabrication of YBCO melts textured multi-seeded large bulks with three to eight seeds. Except of levitation, magnetization, trapped field and hysteresis, we review system engineering parameters of HTS magnetic linear and rotational bearings like compactness, cryogenics, power density, efficiency and robust construction. We examine mobile compact YBCO bulk magnet platforms cooled with LN 2 and Stirling cryo-cooler for demonstrator use. Compact cryostats for Maglev train operation contain 24 pieces of 3-seed bulks and can levitate 2500–3000 N at 10 mm above a permanent magnet (PM) track. The effective magnetic distance of the thermally insulated bulks is 2 mm only; the stored 2.5 l LN 2 allows more than 24 h operation without refilling. 34 HTS Maglev vacuum cryostats are manufactured tested and operate in Germany, China and Brazil. The magnetic levitation load to weight ratio is more than 15, and by group assembling the HTS cryostats under vehicles up to 5 t total loads levitated above a magnetic track is achieved.
59 citations
TL;DR: In this article, the research and development of high-temperature superconducting wires, especially yttrium-based coated conductors (CCs), and their energy applications have been expected to reduce CO 2 emissions.
Abstract: The research and development of high-temperature superconducting wires, especially yttrium-based coated conductors (CCs), and their energy applications have been expected to reduce CO 2 emissions. This article reviews recent progress in this area, mainly focusing on the results obtained by national projects in Japan. The I c (critical current) × L (wire length) value of CCs has been improved to reach 466,752 A m (572 A/cm-W, 816 m), which exceeds that of Bi-system wires. CCs have also been improved in terms of in-field performance and AC loss reduction to meet market requirements. Power applications such as superconducting magnetic energy storage (SMES) systems, power cables and transformers have been developed using CCs in the current project. Because of fundamental research on high-capacity power cables, a low AC loss of 0.8 W/m-ph at 3 kA and 73.7 K was achieved. System design and fundamental research were performed on a 2GJ-class SMES system and a 20 MVA-class transformer. Based on the technologies developed by the end of the current project (FY2012), the innovation process of those applications will reach the implementation stage, where the long-term reliability tests will be performed. The process is expected to reach the penetration and propagation stage around 2020.
57 citations
TL;DR: In this article, the critical current density (J c ) and the grain boundary property of BaFe 2 (As,P) 2 thin films grown on MgO single crystal or bicrystal substrates by molecular beam epitaxy were investigated.
Abstract: We have investigated the critical current density ( J c ) and the grain boundary property of BaFe 2 (As,P) 2 thin films grown on MgO single crystal or bicrystal substrates by molecular beam epitaxy. We found a strong correlation between J c and the Fe/Ba composition ratio, and a very large self-field J c of 1.2 × 10 7 A/cm 2 at 4.2 K with a thin film for which the Fe/Ba ratio was 2.4. A grain boundary junction was fabricated by growing a thin film on a MgO bicrystal substrate having a misorientation angle of 24°. The inter-grain J c at 4.0 K recorded 10 6 A/cm 2 , which is higher than that of YBa 2 Cu 3 O y . These results demonstrate the high potential of BaFe 2 (As,P) 2 in practical applications and indicate that the necessary condition for in-plane alignment is less severe than YBa 2 Cu 3 O y .
50 citations
TL;DR: In this paper, a simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors.
Abstract: A simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors. The copper stabilizer layer is selectively electroplated on the superconducting filaments while the striations remain copper-free due to the formation of a resistive oxide layer in between filaments by oxidation of the striated grooves at elevated temperature in oxygen atmosphere. Magnetization AC loss measurements, performed in a frequency range of 45–500 Hz at 77 K, confirmed the expected N-fold reduction in AC loss of the filamentized tapes with no significant degradation in critical current beyond that due to the material removal from the striations (N – number of filaments). A considerable reduction in coupling AC loss was observed after high temperature annealing/oxidation of the striated tapes. Furthermore, a significant reduction in eddy current loss was achieved with selective copper electroplating, as evidenced by analyzing the field and frequency dependence of magnetization AC loss, as well as by comparing the AC loss performance of striated samples to that of non-striated samples after electroplating of copper stabilizer.
50 citations
TL;DR: In this article, the influence of praseodymium content on the basis plane conductivity of Y 1− х Pr ͅ Ba 2 Cu 3 O 7− δ single crystals was investigated.
Abstract: We investigate the influence of praseodymium content on the basis plane conductivity of Y 1− х Pr х Ba 2 Cu 3 O 7− δ single crystals. An increase of the praseodymium concentration leads to the enhancement of the localization effects and the appearance of a metal–insulator transition in the system, which always precedes the superconducting transition. The increase of the concentration of praseodymium, leads to a significant displacement of the point of the metal–insulator transition in the low temperature region.
46 citations
TL;DR: In this paper, a soft etching procedure was used to preserve the shape pristine superconducting properties of YBa2Cu3O7-x nanowires, with lateral dimensions smaller than 50 nm, by adding an Au capping layer on top of the nanostructure.
Abstract: YBa2Cu3O7-x nanowires, with lateral dimensions smaller that 50 nm have been fabricated by a soft etching procedure preserving an Au capping layer on top of the nanostructure. We have obtained YBCO nanowires carrying critical current densities J(c) close to the theoretical depairing limit. The resistive transition and the J(c) as a function of temperature of the Au capped nanostructures have been compared with those where the Au protective layer was subsequently removed. We conclude that the Au capping layer together with the soft etching procedure are instrumental in preserving shape pristine superconducting properties very close to the as grown film. Our results open new perspective for the use of YBCO nanostructures in fundamental studies aiming at shedding light on the mechanism for high critical temperature superconductivity. (C) 2013 Elsevier B.V. All rights reserved.
42 citations
TL;DR: In this paper, an attempt has been made to improve THz radiation characteristics emitted from mesas made from Bi2Sr2CaCu2O8+δ single crystals in order to achieve the ultimate goal of high frequency quantum device applications, named here as the Quantum Terahertz Electronics (QTE).
Abstract: An attempt has been made to improve THz radiation characteristics emitted from mesas made from Bi2Sr2CaCu2O8+δ single crystals in order to achieve an ultimate goal of high frequency quantum device applications, named here as the Quantum Terahertz Electronics (QTE). Among many requirements to be fulfilled and necessary for the development, we here made an effort to generate more intense radiation using a stand-alone type of mesa. Some characteristic features are described.
41 citations
TL;DR: In this article, the authors presented the synthesis and characterization of Bi 2 Sr 2 CaCu 2 O 8+ x superconducting nanowires with a T c ǫ = 78.7 K. They used a sol-gel methodology to obtain a homogeneous PVP solution containing Bi, Sr, Ca, and Cu acetates.
Abstract: This paper presents the synthesis and characterization of Bi 2 Sr 2 CaCu 2 O 8+ x superconducting nanowires. Bi 2 Sr 2 CaCu 2 O 8+ x nanowires with a T c = 78.7 K are synthesized using the electrospinning process employing sol–gel precursors. A sol–gel methodology is used to obtain a homogeneous PVP solution containing Bi, Sr, Ca, and Cu acetates. Mats of randomly oriented nanowires and aligned nanowires are also collected. After a heat treatment at 850 °C in ambient atmosphere using heating rates of 100 and 400 °C/h, fully crystallized Bi 2 Sr 2 CaCu 2 O 8+ x nanowires are obtained. The morphology, microstructure, and crystal structure of these nanowires are then examined to reveal a rectangular morphology having typical wire thickness in the range of 150–250 nm, and a wire width between 400 and 600 nm. DC magnetization studies are conducted to investigate the critical transition temperature ( T c ) of Bi 2 Sr 2 CaCu 2 O 8+ x nanowires and to compare their magnetic properties to those of bulk Bi 2 Sr 2 CaCu 2 O 8+ x powder. The T c for the commercial powder is observed at 78.6 K, and that of the obtained nanowires at 78.7 K. These results point to the superconducting nature of Bi 2 Sr 2 CaCu 2 O 8+ x nanowires, and the potential of the electrospinning process for the synthesis of this superconductor material.
39 citations
TL;DR: In this article, the authors proposed an application of the 100kWh superconducting flywheel energy storage systems to reduce the peak power of the electric railway system, which can guarantee the secure capacity of electrical equipment and the low utilization rate of regenerative energy limits the significant energy efficiency improvement.
Abstract: This paper proposes an application of the 100 kWh superconducting flywheel energy storage systems to reduce the peak power of the electric railway system. The electric railway systems have high-power characteristics and large amount of regenerative energy during vehicles’ braking. The high-power characteristic makes operating cost high as the system should guarantee the secure capacity of electrical equipment and the low utilization rate of regenerative energy limits the significant energy efficiency improvement. In this paper, it had been proved that the peak power reduction and energy efficiency improvement can be achieved by using 100 kWh superconducting flywheel energy storage systems with the optimally controlled charging or discharging operations. Also, economic benefits had been assessed.
35 citations
TL;DR: In this article, the superconductivity of Lu2SnC with the Tc of 5.2 K was discovered and the properties of superconducting parameters were measured as functions of temperature and magnetic field.
Abstract: We discovered the superconductivity in Lu2SnC with the Tc of 5.2 K. Lu2SnC crystallizes in a hexagonal structure (Cr2AlC-type) with the space group of P63/mmc. We measured the physical properties of Lu2SnC in the superconducting state as functions of temperature and magnetic field. The M–H curve shows the typical type-II superconducting behavior. Superconducting parameters Hc1(0), Hc2(0), λ(0), ξ(0) and κGL are determined to be about 110 Oe, 4.5 kOe, 250 nm, 27 nm, and 9.2, respectively.
TL;DR: Based on BCS theory with moving Cooper pairs, the electron states distribution at 0 k and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field.
Abstract: Based on BCS theory with moving Cooper pairs, the electron states distribution at 0 K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.
TL;DR: In this article, the authors demonstrate that the thin-film synthesis of LaNiO2 is rather easy, thanks to a large surface-to-volume ratio, which makes oxygen diffusion prompt.
Abstract: Infinite-layer LaNiO2 thin films were synthesized by metal organic decomposition and subsequent topotactic reduction in hydrogen, and their transport properties were investigated. LaNiO2 is isostructural to SrCuO2, the parent compound of high-Tc Sr0.9La0.1CuO2 with Tc = 44 K, and has 3d9 configuration, which is very rare in oxides but common to high-Tc copper oxides. The bulk synthesis of LaNiO2 is not easy, but we demonstrate in this article that the thin-film synthesis of LaNiO2 is rather easy, thanks to a large-surface-to-volume ratio, which makes oxygen diffusion prompt. Our refined synthesis conditions produced highly conducting films of LaNiO2. The resistivity of the best film is as low as 640 μΩ cm at 295 K and decreases with temperature down to 230 K but it shows a gradual upturn at lower temperatures.
TL;DR: In this paper, the effects of sintering temperature and Sn addition on the phase formation, resistivity transition, critical current density and microstructure of Sr-122 tapes were investigated.
Abstract: We report a systematic investigation on the effects of sintering temperature and Sn addition on the phase formation, resistivity transition, critical current density and microstructure of Sr-122 tapes. With increasing sintering temperature from 800 to 950 °C, the a -lattice parameter of Sr122 + Sn samples slightly elongates while c -lattice parameter shrinks. The composition of superconducting phase was affected by different sintering conditions with Sn addition. It is found that the grain connectivity of Sr122 + Sn samples is greatly enhanced while higher content of FeSn impurity and structure defects are introduced at higher sintering temperature. The samples sintered at 900 °C show a maximal transport J c value in self-field whereas the field independence of J c for the samples sintered at 850 °C is optimal. On the other hand, comparing with the pure samples, the Sn-added samples present well connected cake-like grains, growth steps and a large number of dislocations, resulting in high transport J c properties. It is proposed that molten Sn enters the rim of Sr-122 phase and greatly accelerates the dissolution of misfit at the edges of grains within a short sintering time, and subsequently reduces the interfacial energy. Our results indicate that moderate Sn addition in combination with optimized heating conditions is very promising for high J c -H performance.
TL;DR: In this article, the intensity and coherent terahertz (THz) electromagnetic (EM) waves emitted from equilateral triangular mesa structures of the intrinsic Josephson junctions (IJJ) in single crystalline high-Tc superconducting Bi2Sr2CaCu2O8+δ.
Abstract: We report on intense and coherent terahertz (THz) electromagnetic (EM) waves emitted from equilateral triangular mesa structures of the intrinsic Josephson junctions (IJJs) in single crystalline high-Tc superconducting Bi2Sr2CaCu2O8+δ. The focused ion beam milling technique is used for mesa fabrication. THz radiation is observed when the emission frequency is in the vicinity of the primary cavity resonance frequency determined by the mesa geometry. We also investigated numerically the THz radiation from such mesas using the finite difference time domain method. We found an apparent EM mode similar to the known TM(1, 0) = TM(0, 1) cavity mode during the THz emission.
TL;DR: In this article, a flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs) and the flywheel was rotated contactless over 2000rpm which was a frequency between its rigid body mode and elastic mode.
Abstract: We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated.
TL;DR: In this paper, the effect of compaction pressure applied to the Y 2 BaCuO 5 (Y-211) preform during its fabrication, on the final microstructures and current densities (J c ) is investigated.
Abstract: The effect of compaction pressure applied to the Y 2 BaCuO 5 (Y-211) preform during its fabrication, on the final microstructures and current densities ( J c ) is investigated. The necessity for optimizing the sintering conditions in order to provide mechanical stability to the preform prior to the infiltration of liquid phases is demonstrated. The sample fabricated under optimized conditions showed J c values better than 10 3 A cm −2 up to applied magnetic fields of 6.5 Tesla at 77 K. The microstructural factors influencing the field dependence of J c ‘ J c ( H )’ at low and high fields are investigated. Extensive nano-twinning with large number of crossing twins observed in the optimized sample and the associated high defect densities are correlated to be the source of flux pinning to high fields. The fact that YBa 2 Cu 3 O 7− δ (YBCO, Y-123) superconductor obtained employing the present Preform Optimized Infiltration and Growth Process (POIGP) yields a homogenous and dense distribution of fine Y-211 particles, that creates suitable twin/defect densities to provide flux pinning at high fields, is of technical importance.
TL;DR: In this paper, the sintering conditions of disk shaped bulk MgB 2 superconductors with respect to the trapped field were investigated and the highest trapped field was achieved.
Abstract: The optimization of the sintering conditions of disk shaped bulk MgB 2 superconductors with respect to the trapped field is described. Series of samples were prepared by varying the sintering temperatures between 700 and 950 °C. The temperature range was divided into three regions, namely the low ( 850 °C) temperature region. Scanning electron microscopy and X-ray diffraction indicated that homogenous single phase MgB 2 bulks were produced in the medium sintering temperature range. At this processing temperature range the highest trapped field was also achieved. Samples of 20 mm in diameter and 7 mm thick produced at 775 °C exhibited trapped field of 1.50 T at 20 K.
TL;DR: The simulation results show that if an SMES unit is installed in an interconnected power system, in addition to eliminating oscillations and deviations, the settling time in the frequency and tie-line power flow responses is considerably reduced.
Abstract: This paper proposes the combination of a load frequency control (LFC) with superconducting magnetic energy storage (SMES) to solve the LFC problem in interconnected power systems. By using this combination, the speed damping of frequency and tie-line power flow deviations is considerably increased. A new control strategy of SMES is proposed in this paper. The problem of determining optimal parameters of PID and SMES control loop is considered as an optimization problem and a pattern search algorithm (PS) optimization is employed to solve it. The simulation results show that if an SMES unit is installed in an interconnected power system, in addition to eliminating oscillations and deviations, the settling time in the frequency and tie-line power flow responses is considerably reduced.
TL;DR: In this article, a test frame which gives precisely aligned transverse load was devised using the fixture, the delamination behaviours including the delamination strength of 2G coated conductor (CC) tapes under transverse tensile loading were investigated.
Abstract: The electromechanical property behaviour of 2G coated conductor (CC) tapes fabricated by multi-layer deposition process both in the in-plane and transverse direction should be understood. The CC tapes are used in the fabrication of epoxy resin-impregnated coils. In such case, the Lorentz force due to the high magnetic field applied as well as the thermal stress due to the difference in coefficient of thermal expansion (CTE) among constituent layers during cooling to cryogenic temperature will induce transversely applied load to the surface of CC tapes in coils. Hence, the CC tape should have a good mechanical property in the transverse direction in order to maintain its superior performance under magnetic field. In this study, a test frame which gives precisely aligned transverse load was devised. Using the fixture, the delamination behaviours including the delamination strength of the GdBCO CC tapes under transverse tensile loading were investigated. Large variation on the delamination strength of the CC tapes was recorded and might have resulted from the slit edge effect and the inhomogeneity of the CC tapes. The Ic degradation behaviour under transverse load was related to the location where delamination occurred in the sample.
TL;DR: In this article, the authors consider the Hubbard model in terms of the perturbative diagrammatic approach (UN F ⩽ 1 ) where the interaction between two electrons with antiparallel spins in the lowest order of perturbation is described by the short-range repulsive contact (on-site) interaction (U > 0 ).
Abstract: We consider the Hubbard model in terms of the perturbative diagrammatic approach ( UN F ⩽ 1 ) where the interaction between two electrons with antiparallel spins in the lowest order of perturbation is described by the short-range repulsive contact (on-site) interaction ( U > 0 ). We argue that in layered 2D cuprates the long-range order antiferromagnetism is driven mainly by the Van Hove singularity, whereas in the case of pnictides the antiferromagnetism exists as a result of the nesting condition. We show that when the interaction is quite strong ( UN F ≈ 1 ) in the case of the Van Hove singularity the electron system undergoes the antiferromagnetic phase transition with the log-range order parameter and large insulating gap. The long-range antiferromagnetism quickly disappear, as shown, with the doping away from the Van Hove singularity, but the antiferromagnetic short-range correlation persists (UNF
TL;DR: In this paper, the effect of Bi2O3 additions on the growth morphology, microstructure and levitation force of the YBCO bulk superconductor has been investigated.
Abstract: Single domain YBCO superconductors with different additions of Bi2O3 have been fabricated by top seeded infiltration and growth process (TSIG). The effect of Bi2O3 additions on the growth morphology, microstructure and levitation force of the YBCO bulk superconductor has been investigated. The results indicate that single domain YBCO superconductors can be fabricated with the additions of Bi2O3 less than 2 wt%; Bi2O3 can be reacted with Y2BaCuO5 and liquid phase and finally form Y2Ba4CuBiOx(YBi2411) nanoscale particles; the size of the YBi2411 particles is about 100 nm, which can act as effective flux pinning centers. It is also found that the levitation force of single domain YBCO bulks is increasing from 13 N to 34 N and decreasing to 11 N with the increasing of Bi2O3 addition from 0.1 wt% to 0.7 wt% and 2 wt%. This result is helpful for us to improve the physical properties of REBCO bulk superconductors.
TL;DR: In this article, single crystals of Ir 1− x Pt x Te 2 were synthesized and characterized, and a broad hysteresis of magnetization throughout a wide range of temperatures in pure IrTe 2.
Abstract: Single crystals of Ir 1− x Pt x Te 2 were synthesized and characterized. The low-temperature monoclinic phase of IrTe 2 is suppressed and disappears with slight Pt doping. The breaking of the Ir–Ir bonds, a characteristic of the low-temperature monoclinic phase in pure IrTe 2 , is accompanied by the emergence of a superconducting phase. The Pt-content dependence of the structural phase-transition temperature and the superconducting transition temperature in single crystals adequately reproduced those in polycrystals. We also found a broad hysteresis of magnetization throughout a wide range of temperatures in pure IrTe 2 .
TL;DR: In this article, the transverse magnetic (TM) electromagnetic modes for thin equilateral cavities of triangular Bi2Sr2CaCu2O8+δ mesas were calculated.
Abstract: In order to understand the radiation observed from the intrinsic Josephson junctions in triangular Bi2Sr2CaCu2O8+δ mesas, we calculate the transverse magnetic (TM) electromagnetic modes for thin equilateral cavities. A new set of distinct but degenerate TM modes coexists with the known modes of Helszajn and James, but are expected to lead to distinct radiation angular distribution patterns. Although we have been unable to solve for the exact TM modes of a thin cavity of general acute isosceles triangular shape, we solved exactly the closely related problems of the TM cavity modes of two thin circumscribing “pie-shaped” wedges, which provide highly accurate approximations to very acute isosceles triangular cavities.
TL;DR: In this paper, the technical feasibility of energy storage technologies for renewable intermittent sources like wind and solar generation is analyzed, and different combination modes of EH storage technologies are proposed, including superconducting magnetic energy storage systems (SMESs), flywheels (FWs), electrochemical super-capacitors (SCs), and redox flow batteries (RFBs).
Abstract: Huazhong University of Science and Technology is planning to establish a hybrid solar–wind generation dynamic simulation laboratory. Energy storage technologies will be vital to this system for load leveling, power quality control and stable output. In this paper, the technical feasibility of energy storage technologies for renewable intermittent sources like wind and solar generation is analyzed. Furthermore, the different combination modes of energy storage technologies are proposed. The involved energy storage technologies include superconducting magnetic energy storage systems (SMESs), flywheels (FWs), electrochemical super-capacitors (SCs) and redox flow batteries (RFBs). Based on that, the economic analysis of hybrid energy storage technologies is conducted.
TL;DR: In this paper, a large bore magnet coil wound without turn to turn insulation was fabricated and cooled down to 10K by conduction cooling, which is a possible option for making compact magnet coil with sufficient structural integrity, thermal and electrical stability at the same time.
Abstract: A large bore magnet coil wound without turn to turn insulation was fabricated and cooled down to 10 K by conduction cooling. The coil has room temperature bore of 102 mm in diameter and consists of 22 double pancakes wound with 2G HTS conductor on aluminium alloy bobbin. Tests for 22 double pancake coils were performed at 77 K for individual single DPC, coupled 2 DPCs, 4 DPCs, 8 DPCs and 22 DPCs. Tested DPCs were connected by splice joint and assembled coil structure was installed to the vacuum cryostat with radiation shield and cooled down to 10 K for 28 h. The coil generate 4.1 T when operating current ramped to 200 A by 0.1 A/s without quench. Test results agreed well with the designed performance showing field homogeneity of 0.021% for radial axis and 0.056% for vertical axis in 10 mm DSV at 4.1073 T. The magnet showed quench at 210 A when ramping rate was 0.15 A/s at 10 K. The results showed that without turn to turn insulation winding method is a possible option for making compact magnet coil with sufficient structural integrity, thermal and electrical stability at the same time.
TL;DR: In this article, the X-ray diffraction patterns of Ag doped samples were found to indicate that the Ag is doped into the lattice site of FeSe 0.5 Te 0.05.
Abstract: Ag added bulk FeSe 0.5 Te 0.5 samples Ag x (FeSe 0.5 Te 0.5 ) 1− x were prepared by solid-state reaction. The x , nominal concentration of Ag, was ranged between 0 and 0.08. The mixed powder was first put into an alumina tube and sealed in an evacuated quartz tube that was heated at 1323 K for 20 h. Subsequently, it was cooled to 673 K and annealed for 200 h to stabilize the superconductive layers. The pure Ag or Ag compound was not observed in the X-ray diffraction patterns of Ag doped samples. It indicates that the Ag is doped into the lattice site of FeSe 0.5 Te 0.5 . The T c is about 14 K up to x = 0.04, but the T c decreases gradually to 11 K above x = 0.05. The magnetization decreased with increase of x , but a fishtail-like hump was observed for x = 0.05 sample. The magnetic hysteresis of x = 0.05 sample is larger than that of x = 0 sample above 2 T .
TL;DR: Analysis of the operating characteristics of a superconducting magnetic energy storage (SMES) for the frequency control of an islanded microgrid operation shows that the SMES contributes well for frequency control in the islanded operation.
Abstract: This paper analyzes the operating characteristics of a superconducting magnetic energy storage (SMES) for the frequency control of an islanded microgrid operation. In the grid-connected mode of a microgrid, an imbalance between power supply and demand is solved by a power trade with the upstream power grid. The difference in the islanded mode is a critical problem because the microgrid is isolated from any power grid. For this reason, the frequency control during islanded microgrid operation is a challenging issue. A test microgrid in this paper consisted of a wind power generator, a PV generation system, a diesel generator and a load to test the feasibility of the SMES for controlling frequency during islanded operation as well as the transient state varying from the grid-connected mode to the islanded mode. The results show that the SMES contributes well for frequency control in the islanded operation. In addition, a dual and a single magnet type of SMES have been compared to demonstrate the control performance. The dual magnet has the same energy capacity as the single magnet, but there are two superconducting coils and each coil has half inductance of the single magnet. The effectiveness of the SMES application with the simulation results is discussed in detail.
TL;DR: In this paper, the effect of the choice of infiltration temperature 1040°C and 1100°C on the microstructure, magnetic properties and mechanical strength of Y 2 BaCuO 5 (Y-211) preform in achieving high current densities to high magnetic fields has recently been established.
Abstract: The importance of optimizing the fabrication of the Y 2 BaCuO 5 (Y-211) preform in achieving high current densities to high magnetic fields has recently been established. We report the effect of the choice of infiltration temperature 1040 °C (sample A) and 1100 °C (sample B) on the microstructure, magnetic properties and mechanical strength. Both the samples showed [1 0 3] texture after slow cooling through peritectic temperature. Infiltration at higher temperature is found to yield highly dense composites with minimal macrodefects and higher hardness of 18.73 GPa in sample B. Both the samples show uniform distribution of Y-211and comparable zero-field critical current density. High current densities are retained to a higher field of 7 T in sample B, unlike 2 T in sample A. The occurrence of [1 0 3] texture promoting higher hardness, simultaneous with retention of considerably high current density to high fields in sample B has definite advantages for trapped field applications.
TL;DR: In this paper, the authors investigated the distribution of AC loss for a storage magnet on different operating conditions, which is based on finite element method (FEM) and measured properties of BSCCO/Ag tapes.
Abstract: The AC loss induced in superconducting tape may affect the performance of a superconducting device applied to power system, such as transformer, cable, motor and even Superconducting Magnetic Energy Storage (SMES). The operating condition of SMES is changeable due to the need of compensation to the active or reactive power according to the demand of a power grid. In this paper, it is investigated that the distribution of AC loss for a storage magnet on different operating conditions, which is based on finite element method (FEM) and measured properties of BSCCO/Ag tapes. This analytical method can be used to optimize the SMES magnet.