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The superconducting motor generally adopts superconducting magnets to supply high flux density in the air-gap around the rotor. This structure can decrease the volume as a result of the high magnetic load, but it also creates cooling difficulty problems due to the cooling medium's spin sealing. Therefore, the superconducting magnets need frequent maintenance, and this structure cannot be applied in the industry field. So a novel high temperature superconducting motor with a superconducting armature coils is researched. This motor's stator uses ferromagnetic material and the superconducting windings are located in the slots. The ferromagnetic material can decrease the magnetic field in the superconducting coils, so the current carrying ability of the superconducting coils can be increased. The rotor adopts the permanent magnets as the excitation. Such design details of the motor can ensure the superconducting coils can undertake larger current and reduce AC loss. In this paper the electromagnetic field distribution of the HTS motor stator coils is analysed. Finally, the detailed HTS motor parameters are presented to analyse the output torque characteristic. From the characteristics, it can be seen that the novel HTS motor has the same power density as the traditional HTS motor. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel power system protection scheme in the power system including high temperature superconducting cables (HTS cables) and high temperature superconducting fault current limiters (HTSFCLs). The superconducting power system utilizes the large-capacity and environment-friendly characteristics of superconducting power equipment. Since the superconducting devices are one of the most optimal solutions to enhance the robustness of the power system, especially in Icheon substation in Korea, the protection of the conservative relays and additional relays, differential and instantaneous overcurrent relays, should be alternated with a new optimal protection coordination under the changed system configurations. To find the optimal protection scheme, the power system with existing power devices, conservative relays, HTS cables, and fault current limiter has to be modeled in Icheon substation and the novel protection scheme has been verified through RTDS test with real-time relay test. [ABSTRACT FROM PUBLISHER]

This paper presents quench test results, of both experiment and simulation, of a racetrack pancake coil wound with a GdBCO-coated conductor tape in a solid nitrogen (SN2) cooling system at 58 K. The longitudinal normal zone propagation velocities in the curved section were 2 times faster than those in the straight section. Therefore, the straight section should be protected more than the curved section when using racetrack-type, GdBCO pancake coils in large-scale rotating machines. The simulated results showed good agreement with the experimentally observed normal zone initiation times. [ABSTRACT FROM PUBLISHER]

This paper describes a operating characteristics of contactless power transfer (CPT) system from normal conducting coil to HTS coil based on the electromagnet resonance coupling. The basic principle is that two separate coils with same resonance frequency are possible to form a resonant system based on high frequency magnetic coupling and exchange energy in a high efficiency. The CPT technique with the electromagnetic resonance coupling has been expected as a useful option for contactless charge and storage devices. Since the CPT technology using normal conducting coils is sensitive to tune impedance matching, the transfer power efficiency is limited. From this reason, we proposed the combination CPT technology with superconducting receiver coils, it is called as, superconducting contactless power transfer (SUCPT). The SUCPT system can reduce joint loss of superconducting connection and increase the portability of the superconducting system. In this study, as a fundamental step, the optimal power transfer conditions needed to generate inductive power transfer between normal conducting coils and superconducting coil were experimentally examined. The power transfer profile for coupled resonance coils with high frequency power was investigated in order to minimize operating power. [ABSTRACT FROM PUBLISHER]

This paper introduces the design methodology of HTS bulk generator for direct-driven wind turbine. The trap field capability of HTS bulks offer the potential of maintaining similar or even higher magnetic loading level without the iron circuit in the generator. This so-called air-cored design can reduce the weight and increase the power outing per volume of the machine. The detailed design method of the air-cored HTS bulk machine is presented; 3D modeling is applied to consider the total trapped field of bulk arrays; a case study is performed to demonstrate the advantages of air-cored HTS bulk machine over conventional permanent magnet machine. Our results show that the air-cored HTS bulk machine has the potential to maintain the same magnetic loading level as that of the conventional permanent magnet machine. More importantly, it can reduce the total machine weight by 30%. [ABSTRACT FROM PUBLISHER]

In a High Temperature Superconducting (HTS) magnet consisting of pancake windings, HTS tape with the same width has been used for all pancake windings. If a wider HTS tape is used for the outer pancake windings, the critical current of the HTS magnet can be increased. This paper shows the properties of BSCCO magnets in which the outer pancake windings are wound with a wider HTS tape. In order to examine the effects of a wider HTS tape, a HTS magnet with an inner radius of 20 mm and a height of 202.4 mm was used. The number of turns of each pancake winding was 150, and the number of pancake windings was 46. The critical current of the pancake winding was determined by using E-J relation. Results of calculation show that the critical current was higher in the HTS magnet with a wider HTS tape at the outer pancake windings than in the HTS magnet with the same width of HTS tape for all pancake windings. [ABSTRACT FROM PUBLISHER]

In order to continue supporting the development of accelerator magnets for the next generation of particle colliders, the LBNL Superconducting Magnet Program has started the design and fabrication of the Nb3Sn Large-aperture Dipole LD1. The goal of the magnet is to generate a dipole field of 13 T to 15 T in a clear aperture of 144 mm \times 94 mm, enabling high-field tests of Rutherford cables and insert coils made of Nb3Sn or high temperature superconductors (HTS), like Bi-2212, YBCO, and Bi-2223. The bore size will also accommodate large Cable-In-Conduit Conductors (CICC's), including ITER cables. We describe in this paper the design of LD1, in particular cable geometry, coil lay-out and support structure. Operational conditions based on strand measurements will be discussed, focusing on coil peak fields in straight section and end region, bore field homogeneity, and stress on the conductor during assembly, cool-down and excitation. [ABSTRACT FROM PUBLISHER]

The knowing the critical current density JC is important to calculate AC losses in superconducting applications. Usually JC can be obtained from magnetization measurements or electric measurements based on global quantities as the magnetic flux or the voltage. In this paper a quick and direct magnetic method for determining JC is proposed. It is based on direct measurements of local magnetic field in the gap between two bulk HTS pellets. Field penetration measurements were carried out on HTS pellets at 77 K by applying increasing axial magnetic fields with a quasi constant sweep rate. This determination of JC is theoretically based on Bean model. JC is deduced from the complete penetration magnetic field BP. BP is deduced from the delay TP between the applied magnetic field Ba(t) and the magnetic field at the center between the two pellets B0(t). Numerical calculations allow deducing JC more precisely from theoretical calculations and measurements. The numerical calculations are made with the power law E=EC(J/JC)^{n}. For the determination of JC the influence of the gap due to Hall probe sensor and the applied magnetic field rise rate are taken into account. The influence of thermal is also studied. [ABSTRACT FROM PUBLISHER]

We have been developing superconducting induction /synchronous motor incorporated with MgB2 cage windings. Target application of the motor is the liquid hydrogen circulation pump. In this paper, the performance of the fabricated motor was estimated based on nonlinear electrical equivalent circuit. It was shown that the experimental results of the motor characteristics such as torque vs. slip curve can be reproduced based upon the theoretical estimation. From this result, we can design the MgB2 pump motor by means of commonly utilized method of the electrical circuit. [ABSTRACT FROM PUBLISHER]

The high temperature superconducting (HTS) power cable has been successfully installed and operated for feasibility confirmation since 2006 at the power testing center of Korea Electric Power Corporation (KEPCO). The three phase 100 m long HTS cable with 22.9 kV/1.25 kA was manufactured and cooled by the open-loop of sub-cooled liquid nitrogen generated by a decompression cooling unit. No major fault has been observed during long-term operating test. As a next step, the design study of a 500 m long HTS cable system has initiated in 2008. Now, the HTS power cable was manufactured and installed at Icheon substation located near Seoul. In this paper, the cooling performance test of the 500 m long HTS cable in the real power grid is reported. Pre-cooling process using nitrogen gas is presented and the result of initial cool-down of the HTS cable is reported. Also, temperature as well as pressure drop in the system is discussed with respect to the loading current level. [ABSTRACT FROM PUBLISHER]

The paper reports on experimental and numerical studies of AC loss in a high temperature superconducting coil wound with a Bi2223/Ag tape. A measurement method of the AC loss in the HTS coil by using a power meter is proposed. The AC loss is measured on the test HTS coil made by stacking pancake coils wound with the Bi2223/Ag tape. The AC loss is also calculated using the numerical method developed in our previous work. The measured AC loss is compared with the calculated one. The agreement of measured and calculated data is reasonable and this shows the validity of the proposed measurement method. [ABSTRACT FROM PUBLISHER]

As a variation of the thermally actuated flux pump and the linear type magnetic flux pump (LTMFP), the circular type magnetic flux pump (CTMFP) device is proposed to magnetize a circular shape type-II superconducting thin film and bulk. The basic concept is the same as the thermally actuated flux pump: a circularly symmetric traveling magnetic field is generated below a circular shape superconductor to increase its trapping field. However, this traveling field is created by the three phase windings instead of heating gadolinium block. Apart from the LTMFP, the three phase windings are wound concentrically instead of linearly. The speed of the traveling field is controlled by the AC frequency and the magnitude of the field is controlled by the magnitudes of AC currents. In addition, a coil with DC current is wound around the three phase windings to provide a background field. The concept design is presented in this paper. The magnetic waveforms are analysed numerically by the COMSOL 3.5a software. The impedances of the three phase windings are calculated and a corresponding circuit design is presented. This rig can be used as an advanced tool to study the flux pump behavior of a circular shape superconductor. [ABSTRACT FROM PUBLISHER]

For the magnet used in power apparatus, the inductance is an important parameter which may change the input-output characteristic of the apparatus. In research of the high temperature superconducting (HTS) magnet in energy storage system and other electric apparatus, we found the difference of the magnet's inductance between normal state and superconducting state. In this paper, the electromagnetic models of Bi2223/Ag tape and windings are established firstly. Based on the simulation analysis and measured results, the reason of inductance variation of HTS magnet has been clarified. The regularity of inductance variation of HTS pancake and magnet has been researched, and new requirement for the veracity in the process of superconducting magnet's design has been claimed. [ABSTRACT FROM PUBLISHER]

This paper describes the electrical analysis and performance test result of windings of a 10 HP homopolar fully superconducting synchronous motor. The homopolar motor has high temperature superconducting (HTS) armature and field coils. The stationary field coils make the cooling system simple and easy because there is no cryo-moving part. The design of the motor and the analysis of magnetization loss generated in the superconducting armature windings are performed by finite element method. The critical current test results of the 2G superconducting wire, the pancake coil for field winding and the race track coil for armature winding are reported. [ABSTRACT FROM PUBLISHER]

Due to the magnetic anisotropy of a High Temperature Superconducting (HTS) tape, inserting a gap between pancake windings can increase the central magnetic field and improve the field uniformity of HTS magnets consisting of pancake windings. Although inserting gaps with constant length can increase the central magnetic field, optimizing the length of each gap to maximize the central magnetic field is preferred. This paper shows the test results of HTS magnets with and without optimized gaps. Both magnets consisted of 12 BSCCO-2223 pancake windings. The test results were compared with the calculation results, and confirmed that the central magnetic field of the HTS magnet with optimized gap was increased compared with the HTS magnet without gap. The magnetic field uniformity of the HTS magnet was also improved. [ABSTRACT FROM PUBLISHER]

The development of a 5 T high temperature superconducting (HTS) insert magnet system is underway at the Korea Basic Science Institute (KBSI). The objective of the program is the design and fabrication of HTS insert magnet system for high field superconducting magnet applications. Since the HTS magnet system should be inserted into the conduction-cooled 15 T background magnet with 102 mm room-temperature bore, several ancillary requirements such as space restriction and cryostat structure need technical attention. The design and fabrication of the HTS insert cryostat are completed now. In this paper, the design of the cryostat for the 5 T HTS insert magnet is presented, taking into account the cryogenic loads and inventory of cryogenic liquid. In addition, the structure of the cryostat, minimizing thermal flow from room-temperature to cryogenic-temperature, is described in detail. The preliminary results of performance test of the HTS insert cryostat are also discussed. [ABSTRACT FROM PUBLISHER]

There is an increasing interest in installing high-temperature superconductor (HTS) cables to an highly populated metropolitan area to significantly improve power transmission capacity with minimal electrical loss. Regardless of the attractive advantage, the HTS cable could unpleasantly change power flows in the neighboring grid because of reduced series inductance. Reduced damping of the HTS cables due to lower resistance, but with higher capacitance, may have an adverse impact on the power system stability. Thus, inexperienced oscillatory, voltage instability or both issues may occur in the power system. This paper first characterizes the HTS cable with reference to the existing overhead line and cross-linked polyethylene (XLPE) cable. It addresses a few potential challenges in the future power grid due to the expanded adoption of the HTS cables through analytical and simulation studies. The installation of HTS cables using data gleaned from careful studies and relevant reactive compensation schemes should yield a reliable and sustainable electric power infrastructure. [ABSTRACT FROM PUBLISHER]

An HTS magnet was designed for the 1 MJ/0.5 MVA SMES with Bi2223/Ag tapes. According to the design, it consists of 44 double pancakes with an inductance of 6.28 H, and the rated operating current is 565 A, the maximum magnetic field is up to 5.72 T. In this paper, the insulation of the tapes and the magnet, the fabrication and tests of the 44 double pancakes, the joints among double pancakes and the assemblage of the magnet are described in detail. And then, the fundamental performances testing of the magnet were carried out at liquid nitrogen and helium, respectively. With zero helium vaporization, the 1 MJ HTS magnet was dip in liquid helium and cooled with four G-M cryocoolers. After the whole 1 MJ/0.5 MVA SMES were field installed and tested, it had been put into operation since Feb. 16 of 2011 at a 10.5 kV superconducting power substation locating in Baiyin, Gansu Province of China. [ABSTRACT FROM PUBLISHER]

This paper discussed feasibility of bridge-type and multi-layer mechanical lap joint of a stacked HTS conductor. In the multi-layer mechanical lap joint, a decrease in critical current induced by transverse compressive joint force is one of the important factor to decide joint resistance. In addition, misalignment of joint section could be a problem because respective HTS tapes consisting the stacked HTS conductor could have slightly different thickness. In this study, therefore, transverse stress effect on critical current of stacked BSCCO and GdBCO conductors was experimentally investigated at first. Then, bridge-type mechanical lap joints of single layer and 2-layer HTS conductors were tested to confirm their performance and to consider the misalignment of joint section. Experimental results showed that critical current of the BSCCO conductor decreased at lower stress when the number of layers increased whereas that of the GdBCO conductor was less influenced by the stress. Joint resistance in the bridge-type mechanical lap joint was comparable to those in normal mechanical lap joint and soldered lap joint in the case of the single layer. Joint resistances in the 2-layer lap joint were two or three times larger than those in the single layer lap joint due to the misalignment. To solve this problem, compliant metal layer should be inserted into joint section. [ABSTRACT FROM PUBLISHER]

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]

Recently, the smart fault current controller (FCC) was proposed in order to apply to the smart grid. The smart FCC consists of an HTS coil, an AC/DC rectifier, and a control unit. A fault current should be immediately limited by the inductance of the coil at the first peak, and then adjusted by controlling the rectifier. The larger inductance of the coil induces the lower fault current. However, a large inductance coil requires high cost and large size. To reduce the HTS conductor consumption, an HTS coil with a reversely magnetized core (RMC) was proposed. To verify the concept, two permanent magnets were installed. In this paper, various model coils were fabricated and applied to the FCC system: 1) air core, 2) open iron core, 3) closed iron core, 4) open core with RMC, and 5) closed core with RMC. Based on a comparative study on the five models, an HTS coil with a closed RMC has the lowest first peak current. The first peak current in the proposed model was 27.8% smaller than that of air core case. The experimental results show that the proposed concept is to reduce the wire consumption. [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]

Our group has tried to introduce High Temperature Superconducting Technology to electric vehicle (EV) drive motor, and developed High Temperature Superconducting Induction-Synchronous Machine (HTS-ISM). In this paper, 20 kW class HTS-ISM were designed and manufactured with DI-BSCCO wires. First, we developed and tested partial superconducting HTS-ISM (HTS rotor windings with copper stator) for clarification of the performance. We could observe the efficiency at 92.3% even for the light load. Furthermore, we successfully fabricated and conducted no-load test for fully superconducting HTS-ISM. It was verified that stable synchronous rotation at 1200 rpm was succeeded, which is the world-first success of achieving the rotation at over 1000 rpm for fully superconducting motor. Our results are one of the big steps for realizing the HTS-EV. [ABSTRACT FROM PUBLISHER]

A 2.5 MJ Superconducting Magnetic Energy Storage System (SMES) is being developed as a national R&D project in Korea. It is in 2nd phase of total 3 phases program. In phase 1, we developed a 600 kJ SMES which had the maximum storage over 1 MJ. Its magnet was an HTS solenoid, whereas the HTS magnet for phase 2 is a toroid which is composed of 28 HTS double pancake coils. The final target of phase 3 is to develop a 5 MJ SMES, which will start from next year. The operating temperature of the HTS magnet will be below 20 K by conduction cooling. In this paper, we present and compare conceptual designs of the magnet in the shape of toroid and the configuration of serial connection of two 2.5 MJ toroids. The most important design criterion is to minimize the total length of HTS conductors. [ABSTRACT FROM PUBLISHER]

JT-60SA is the satellite tokamak for ITER in the Broader Approach agreement. The JT-60SA uses 18 toroidal field coils, a central solenoid with 4 modules, and 6 equilibrium field coils, they are all superconducting coils with forced flow cooled conductors. All detailed designs of these superconducting coils have been completed. The manufacturing of conductors and coils are progressing in Japan and EU. This paper shows the latest manufacturing activities and final design adjusting of its magnet system and their utilities. [ABSTRACT FROM PUBLISHER]

Many papers report the AC transport current loss characteristics in HTS coils, which occur because the HTS tapes in the coil transport a current in a magnetic field generated by the currents in adjacent tapes. We previously reported our experimental results on the loss from HTS tape in an AC and DC mixed electro-magnetic condition which consists of the DC offset transport current, AC transport current and AC magnetic field. Losses were measured in the same segment by the electric and calorimetric methods, and we established the possibility of measuring the loss using the electric method in the AC and DC mixed electro-magnetic condition. [ABSTRACT FROM PUBLISHER]

In the case of motors and generators, the benefits of using superconductors could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. The high temperature superconducting (HTS) coils wound with HTS conductors have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the conductors have a low thermal conductivity and large specific heat. According to these reasons, in case of HTS coils and magnets, it is difficult to expect the self-protection like as low temperature superconducting (LTS) coils. In this paper, we suggest a method which inserts the Cu tape between turn-turn winding in the HTS coil instead of electrical insulation to improve the self-protection ability of HTS coils. Because the thermal and electrical contacts along the transverse direction are enhanced by inserted Cu tape instead of insulator and the whole thermal stability of HTS coils would be increased. To clarify the quench behavior of this suggested coil, we investigate the normal-zone propagation properties of the fabricated HTS pancake coils wound with 2G conductor and Cu tape under the cryocooled operation using GM cryocooler. The effects of inserted Cu tape and the improved the self-protection ability for the suggested HTS coil will be discussed. [ABSTRACT FROM PUBLISHER]

MRI magnets and other magnets that have a low current and high self-inductance are passively quench-protected with a system that includes sub-divided coils with resistors and diodes that are in parallel with sections of the coils. The primary purpose of coil sub-division is to protect the coil from the high voltages that can occur during a quench. In the event of a lead failure (conventional or superconducting) between the coil and its power supply or its persistent switch, the total current in the coil flows through the diodes and resistors in parallel with the coil. When a lead fails, the current decay time constant for the coil current can be quite long. It is desirable that the coil quench in a time that is short compared to the coil current decay time constant. Experience shows that the heating from the resistors and diodes will eventually quench the magnet. This paper presents methods for shortening the time between a lead failure or a persistent switch failure and the eventual magnet quench. [ABSTRACT FROM PUBLISHER]

A commercial HTS magnet was designed, built and tested by HTS-110 Ltd for X-ray Magnetic Circular Dichroism (XMCD) experiments. The magnet was integrated with a XMCD UHV (Ultra High Vacuum) chamber and installed at an existing soft X-ray beamline at Singapore Synchrotron Light Source (SSLS). The dipole magnet has a bore of 40 mm in diameter and a gap of 90 mm to accommodate the XMCD chamber with nine access ports for sample manipulation and XMCD analysis. To achieve a UHV of 10^-10\ mbar inside the chamber, an independent bakeout system was developed for this magnet to allow the XMCD UHV chamber to be baked out at a temperature over 100 degrees Celsius without affecting the HTS magnet. A small GM type cryocooler is employed to cool the magnet coils down to 17 K by thermally intercepting the heat load from the 2nd stage to the 1st stage. The magnet can provide variable magnetic fields up to 2.16 T and with the field homogeneity better than 0.1% over a 1 cm diameter sphere. Limited by the peak voltage of the bipolar power supply used for the magnet, the minimum time of full field energizing is around 20 seconds and the minimum time of full field reversal is around 40 seconds. The technical issues related to UHV compatibility and ramping rate in developing similar HTS applications are discussed in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents a superconducting filter with a bandwidth of 0.5 MHz at 40 MHz on a \LaAlO3 substrate. It has a compact size of 40 mm \times 19 mm, which amounts to only 0.02\ \lambdag0 \times 0.01\ \lambdag0, where \lambdag0 is the guided wavelength of the 50- \Omega line on the substrate at the midband frequency. The effect of the resonator structure on the unwound length and, hence, the size of the resonator is analyzed. A spiral resonator with positive mutual inductances between adjacent microstrip turns can greatly reduce the resonator's unwound length and is used to miniaturize the filter size. A feedline structure spiraled inside the spiral resonator is proposed to realize a strong external coupling. Furthermore, a cross-coupling line is added to the six-pole filter to improve the band-edge steepness. The filter is successfully designed and fabricated. The measured results demonstrate a 0.3-dB insertion loss, a -19.2 dB return loss, an 80-dB out-of-band rejection, and steep band edges, which are in good agreement with electromagnetic simulations. [ABSTRACT FROM AUTHOR]

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]

This paper presents the design process and test results of a high-temperature superconducting pulsed-power transformer (HTSPPT). The primary winding of the HTSPPT is constructed out of several double-pancake-type coils connected in series. Every double-pancake-type coil is made of Bi2223/Ag tapes. The secondary winding is constructed out of several single-pancake-type coils made of normal conductors. The configuration of the HTSPPT is designed such that the primary and secondary coils are arranged in interleaving. The testing experiments show that a high-current impulse could be achieved with a small current in the primary, which proves that the designed test circuit and the configuration of HTSPPT are feasible. [ABSTRACT FROM AUTHOR]

We propose a high-temperature superconducting fault-current-limiting cable (SFCLC), which is a hightemperature superconducting cable with a fault-current-limiting function. The SFCLC is expected to achieve fault-current limitation by flux-flow resistance of a long cable length. Particularly, in this paper, we focus on E–I –T characteristics of a YBCO-coated conductor at the flux-flow region. Based on the obtained E– I–T characteristics, we develop a numerical model and investigate current-limiting characteristics of the SFCLC for different cable lengths and fault conditions into a model power system. [ABSTRACT FROM AUTHOR]

After clarifying the essential characteristics of the multiseeded YBCO bulk in the previous work, that is, the existence of strongly connected or coupled grain boundaries between two grains by means of intergrain super current with a big flowing loop size, this paper proceeds to report its achievable performance in actual excitation conditions by working as trapped-field magnets or levitation devices. Besides evaluation of the trapped-flux characteristics by two most popular excitation methods, namely, static field-cooling magnetization (FCM) and pulsed-field magnetization in liquid nitrogen (LN2), the trapped-flux capability at lower temperatures up to 30 K, an interesting temperature for present superconducting machine applications, is also reported. From LN2 temperature to 30 K, the trapped flux with over six times improvement from 0.64 to 3.91 T was observed by FCM, at the same time along with a much decreased relaxation rate from 13.7% to 0.9% in 1-h measurements. In the aspect of levitation applications, the magnetic force density (both levitation force and guidance force, two most important performance parameters for maglev) above a permanent magnet guideway with Halbach style is measured and found to be able to promote the loading and stability performance of the first high-temperature superconducting maglev test vehicle simultaneously. As the multiseeding technique of the top-seeded melt-growth process has provided a promising way to fabricate bulk superconductors with large size, time saving and cost reduction, the presented trapped-flux and magnetic force results may help to comprehend, refer, and finally make better use of the multiseeded bulks in the large-scale superconducting magnetic devices. [ABSTRACT FROM AUTHOR]

Detectivity optimization of large-area freestanding-type YBCO superconducting bolometric detectors is theoretically and experimentally investigated. The effect of the device thermal parameters on the theoretical total noise-equivalent power based on background radiation, thermal fluctuation, and Johnson noise is considered. By analytical optimization of the total noise-equivalent power (NEP) of the device with respect to the thermal parameters and radiation modulation frequency, the maximum sensitivity and optimal thermal parameters of the bolometric detector are obtained. Relating device thermal parameters to the special case of the large substrate dimensions, the optimum device geometry is calculated. In addition, several devices with different geometries are fabricated to experimentally test the analysis. By performing experimental optical responsivity and detectivity measurements for these devices, the effect of the geometrical parameters on the maximum sensitivity of bolometric detectors is also empirically obtained. The analytical and experimental results are compared and presented in this paper. [ABSTRACT FROM AUTHOR]

Four coils made of YBCO-coated conductor wire were fabricated and connected in series to make up the excitation system of a linear synchronous motor system with a stator made of ordinary copper wire. The electromagnetic forces experienced by the superconducting coils with respect to the stator were studied in the static case. We began with the study of one single coil, followed by two coils connected in series, and finally, four coils in series from which the largest force obtained was of 53.9 N at a gap of 10 mm at 77 K. The critical current, n-value, and inductance were also measured for the coils so that the power dissipation of the field windings can be calculated. This paper also helps us understand whether linear motors with superconducting components are currently economically feasible with present commercially available superconducting wire. [ABSTRACT FROM AUTHOR]

In this paper, we simulate the effects of eddy currents induced by switched gradient coils in the cylindrical cryostat structures of a high-temperature superconducting (HTS) magnetic resonance imaging magnet. A novel network method was used with spectral decomposition of the current density in the \phi- and z-directions to simulate the effects of X-gradient coils. Two types of active magnetic shielding were simulated, and it was found that one type is able to reduce the power of the eddy currents in the cryostat to a greater extent than the other. These results will inform the design of gradient coils that protect the HTS magnet from eddy-current-induced heating and vibrations. [ABSTRACT FROM AUTHOR]

The origin of high current densities to very high magnetic fields (better than 10^3 \ \A\cdot\cm^-2 to 6.5 T at 77 K) in \YBa2\Cu3\O7 - \delta superconductor fabricated by the preform-optimized infiltration-growth process (POIGP) is investigated. The main techniques used in the paper are field-emission scanning electron microscopy and transmission electron microscopy (TEM). An electron-backscattered-diffraction study of the samples is also carried out. A comparison between the microstructures of the optimized sample with the nonoptimized ones show that extensive twinning on a nanometer scale with crossing twins occurring near the optimally separated \Y2 \BaCuO5 precipitates can be the origin of the observed high Jc(H) in the POIGP sample. The TEM study reveals the presence of very fine defects starting from the twin boundaries. The observed defect spacing and densities account for the uniformly high current densities observed to high fields. [ABSTRACT FROM AUTHOR]

We present the results of a bolometric transition-edge sensor made of a high-Tc superconductor YBCO thin film prepared by fluorine-free metal–organic deposition. The structure of the films was characterized by X-ray diffraction and scanning electron microscopy, and the superconducting properties were determined by R-T measurements. The applicability of the resulting film as an infrared sensor is reported here. The optical response in the range of near infrared and the noise characteristics of the patterned bolometer are measured and analyzed. The dependence of device sensitivity on the bias current and modulation frequency is also investigated. As it is presented in this paper, the results of the fabricated device are comparable to the devices made of high-quality pulsed laser deposition YBCO thin films. [ABSTRACT FROM AUTHOR]

Among superconducting fault-current limiters (FCLs), the inductive type has some distinctive merits such as large design flexibility due to the turn ratio, isolation between a current-limiting device and a power transmission line, and low heat losses. This paper highlights the future perspective for an inductive-type superconducting fault-current limiter (LSFCL) by using an autotransformer (AT) in closed- and open-core schemes. These are considered technically feasible and economically viable alternative for the LSFCL in terms of compactness, efficient limitation, and lower alternating-current losses, which prove to be a construction cost-effective means of fault-current management. In the hybrid scheme, a diode-bridge-type SFCL is integrated with an AT-based LSFCL. The above is accomplished by advanced numerical techniques and, hence, simulation studies in a sample distribution system to realize the significant efficiency improvement of the superconductor-based technology. [ABSTRACT FROM AUTHOR]

Distributed power generation and the ever-growing load demand have caused fault current levels to exceed the nominal rating of the power system devices, and fault current limiters are more needed. Superconducting fault current limiter (SFCL) forms an important category of current limiters. In this paper, a novel flux-based model for the inductive shield-type high-temperature SFCL is developed based on the Bean model. This model is employed to simulate the SFCL performance in a sample circuit. Utilizing the model, the signal characterization of the limited current is determined. A prototype laboratory scale SFCL has been fabricated with superconducting rings. Yttrium barium copper oxide powders have been used for superconducting ring production. The critical current density of fabricated rings has been measured with an innovative method based on application of a magnet device. The fabricated SFCL has been tested in a circuit by applying different types of faults. The related experimental results are recorded and compared with the model results. The results obtained based on the modeling shows full compatibility with the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, we numerically study the influence of the speed variation of a magnetic source on the distribution of current density, magnetization, and dissipated energy of a high-temperature superconducting cylinder described by a J^n power law. The results presented come from the resolution of a nonlinear diffusion problem of electric field by a mixed finite-element finite-volume discretization method. This method is robust, stable, and converges for large values of n. The calculations carried out for n, varying from 1 to 200, show that when the external magnetic field quickly varies from 0 to its maximal value, the maximum values of penetration, the magnetization, and the energy dissipation are obtained when the switching of magnetic field occurs. For a periodic magnetic field, we note that any change of the period results in variation of the magnetization and the dissipated energy. [ABSTRACT FROM AUTHOR]

It is expected that superconducting technologies will play an important role in the future smart grid, because the application of superconductor technologies in the power grid can decrease power losses, relieve overload, avoid higher levels of transmission voltage, increase power transmission capacity, and improve power quality and grid stability. In recent years, high temperature (high-Tc) superconducting power technologies have achieved remarkable progress. High temperature superconducting (HTS) power equipment, such as HTS power cables, HTS transformers, high-Tc superconducting fault current limiters (SFCL), and high-Tc superconducting magnetic energy storage devices (SMES) have been demonstrated in the power grids of many countries. With the development of HTS power equipment, the construction of a HTS power substation is ready. In China, a 10.5 kV HTS power substation is under construction in Baiyin city, Gansu province. The substation integrates a HTS power cable, a HTS transformer, a HTS fault current limiter, and a high-Tc SMES. All these HTS power devices, which were previously developed by the Institute of Electrical Engineering (IEE), Chinese Academy of Sciences (CAS), have been demonstrated to operate for a long time in the commercial power grid. In this paper, the design and constructing progress of the HTS substation are introduced in detail. [ABSTRACT FROM AUTHOR]

In order to design a High Temperature Superconducting (HTS) machine that is able to operate safely and reliably, studies on the characterization of Second Generation (2G) HTS tapes are of paramount importance. This paper presents an experimental setup to measure critical current of 2G HTS tapes in high DC magnetic fields (up to 5 Tesla) with an AC current ripple superimposed, as well as various temperatures ranging from 25 K to 77 K. The 2G tape measured is the SGS12050 coated conductor made by SuperPower. The critical current is measured by a flux vector with reference to the widest sample face from 0 to 90 degrees in 10 degree steps. Smaller steps are required close to 0^\circ. A Variable Temperature Insert (VTI) is utilized to control temperature change. [ABSTRACT FROM AUTHOR]

The seeded infiltration and growth (SIG) technique offers near-net shape processing of bulk superconductors with significant improvement in reduced Y2BaCuO5 (Y-211) inclusion size, reduced shrinkage, reduced porosity and improved current density compared to samples fabricated by top seeded melt growth (TSMG). Y2Ba4CuMOy phases where M=Nb, Mo, W, Ta, etc., have been shown to form nano-scale inclusions in the YBa2Cu3Oy (Y-123) phase matrix and to contribute to enhanced magnetic flux pinning in these materials. In this paper, we describe the introduction of Y2Ba4CuWOy nano-scale inclusions into bulk superconductors processed by the seeded infiltration growth process. Critical current density, Jc, in excess of 10^5\ A/cm^2 at 77 K in self-field is observed for samples containing Y2Ba4CuWOy. [ABSTRACT FROM AUTHOR]

By applying high-rate copper electroplating technique the reliable fabrication of a copper stabilizer on coated conductor with an 1 \mum Ag cap is investigated. The obtained mechanical, electrical and encapsulation properties due to a 20 \mum thick Cu stabilizer on the surface improve the practical and technical performance. A copper sulphate CuSO4 based pulse plating technique is capable to deposit a 20 micrometer thick copper layer in a fast and continuous non-vacuum process. A surround Cu layer protects the HTS conductor surface against salt aqueous solutions, humidity, and against cryogenic liquids LN2 and liquid helium. With the copper stabilizer conductor solder joining with a contact resistance of 200 n\Omegacm^2 becomes possible. Further effort is being made to develop and construct a high-rate and high throughput continuous reel-to-reel modular plating unit for deposition of long length ( >400 m). The paper describes the practical achievements within the conductor fabrication. [ABSTRACT FROM AUTHOR]

Trapped magnetic fluxes in HTS bulks are decayed when the bulks are subjected to perturbation of external magnetic fields. In HTS bulk apparatuses such as HTS bulk motors and magnetic levitation bearings, there is a possibility that the trapped magnetic fluxes in the bulks disappear because the bulks are inevitably subjected to perturbations of the external magnetic fields. For those apparatuses to work stably and reliably, it is necessary to develop methods to suppress the decay. It was shown in our previous experiments that the decay is caused by temperature rises of the bulks due to AC losses in the bulks. The authors proposed a method to put a shorted shielding coil wound of HTS wire around the bulk aiming at reduction of the AC losses in the bulk. It was experimentally shown by use of a shielding coil wound of Bi/Ag sheathed wire that the decay of the trapped magnetic flux was effectively suppressed. In this paper, shielding performance of the coil wound of GdBCO wire was experimentally investigated comparing with that of the coil wound of Bi/Ag sheathed wire. AC losses in the bulks and shielding coils are calculated for various arrangements of the shielding coil to find a preferable shielding coil arrangement from stand points of shielding performance and reduction of AC losses. [ABSTRACT FROM AUTHOR]

High temperature superconductor (HTS) is a promising material as current leads for large current applications, because it has zero resistance. However, a single HTS tape has limitation on the capacity of current rating due to the critical current of the HTS tape. Therefore, stacking or parallel structure of the HTS tapes is inevitable in high temperature superconducting current leads (HTSCLs) for large current application. In this paper, several stacking methods with respect to the shape of the current terminal and the structure of the HTS tape are studied and the characteristics of the stacked samples are investigated by experimental analysis. The critical currents of the HTS modules were measured and the conductive heat leakage of a stabilizer layer was calculated. From this analysis, the characteristics of the current distribution and decrease in the critical current of HTS modules with respect to the shape of the current terminal were obtained. Based on the results, the required stacking number of the HTS tapes for certain operating current HTSCLs can be calculated. [ABSTRACT FROM AUTHOR]

The applications of high-temperature superconductors (HTS) in electric power components have been widely reported and various studies have been made to define their alternating current (AC) losses-a key design parameter for many practical high power electrical engineering applications. However, very few studies over the range 25 to 45 K have been conducted even though this is one of the favored temperature ranges for cost-effective applications of HTS. Methods and techniques used to characterize and measure these losses have been so far grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present an approach using the calorimetric method to accurately determine losses in the superimposed AC and DC fields likely to be experienced in practical devices such as Fault Current Limiters. This technique provides great simplification compared to pick-up coil and lock-in amplifier methods and is applied to a lower temperature range. The preliminary loss data at 40 K will be presented in applied AC magnetic fields with DC fields up to 1T. The data of losses obtained on this sample will allow the estimation and minimization of losses in practical high power HTS coils and will be used in the verification of numerical coil models. [ABSTRACT FROM AUTHOR]

The use of high temperature superconducting (HTS) tapes in a flexible cryostat has been shown to provide great opportunities for the US Navy. The HTS tapes need to be fixed at the ends to provide an electrical connection. Since the ends are rigid but the tapes are contained in a changing environment there is a possibility that the tapes may become twisted and therefore damaged. Twisting is defined in this paper as the rotation of the tape along the length of the tape while the end has no attack-angle. The twisting length and angle of first generation (1G) BSCCO tapes is studied by measuring the voltage drop across the tapes in a liquid nitrogen bath when current is applied. [ABSTRACT FROM AUTHOR]