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This paper presents our new experimental facility and techniques to measure ac loss and current distribution between the layers for High Temperature Superconducting (HTS) cables. The facility is powered with a 45 kVA three-phase power supply which can provide three-phase currents up to 5 kA per phase via high current transformers. The system is suitable for measurements at any frequency between 20 and 500 Hz to better understand the ac loss mechanisms in HTS cables. In this paper, we will report techniques and results for ac loss measurements carried out on several HTS cables with and without an HTS shielding layer. For cables without a shielding layer, care must be taken to control the effect of the magnetic fields from return currents on loss measurements. The waveform of the axial magnetic field was also measured by a small pick-up coil placed inside a two-layer cable. The temporal current distribution between the layers can be calculated from the waveform of the axial field. [ABSTRACT FROM AUTHOR]

Mechanical stresses of magnetically induced origins are becoming more serious with the trend of high-temperature superconductor (HTS) heavy-current transformer (HCT) applications. Mechanical forces in HTS HCTs that act on the transformer windings are generated by the interaction between the current density and the leakage flux density. This paper presents the calculation of leakage flux and mechanical force distribution in high-current HTS transformer windings. This requires the need for advanced numerical techniques for simulation studies using finite-element method by adapting two auxiliary windings for the leakage flux mitigation and, thereby, mechanical forces within the main windings. A model is developed for the calculation of mechanical force considering nonuniformity of both field and current distributions in the windings, which is the main motivation for initiating this paper. [ABSTRACT FROM AUTHOR]

A 68 kA trial-high temperature superconducting current lead for the ITER magnet coil had been developed and tested in parallel with a 52 kA HTS trial lead at ASIPP in Dec. 2008. In order to verify the safety and reliability of HTS section of HTS trial lead, three sub size samples cooled with a GM cooler have been fabricated and tested. Based on the successful sub size HTS module's test results, a novel binary shunt comprising bronze and stainless steel cylinders is applied to HTS trial lead to reduce the conductional heat load to the 5 K cryogenic system and increase the burnout time after quench. This paper gives the numerical calculation of loss of flow accident (LOFA) of HTS trial lead and HTS temperature margin analysis. The measured results of the LOFA and burnout time for the 68 kA trial-HTS current lead are briefly discussed in the paper. The test results indicate the LOFA time is more than 300 s and the burnout time of 21 s is reached more than the requirement of the toroidal field coil fast discharge time of 13 s. [ABSTRACT FROM AUTHOR]

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]

The SMES system with superconducting magnet cooled by SRDK-408 crycooler has been described in this paper. The superconducting magnet consist of 7 double-pancake coils made of Bi-2223 HTS tape with the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is about 1 H. The superconducting magnet is fabricated and tested. In the paper the design and the performance results of the SMES magnet were reported. [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 presents an improved simulated annealing (SA) algorithm for multi-objective optimization, which is a positive approach in the design of high-temperature superconducting (HIS) fault-current limiters (SFCLs). The main goal of this paper is to achieve an effective and feasible approach in the structural design of HTS FCLs by means of multiobjective decision-making techniques, based on normalized SA. The combination of electrical and thermal models of a purpose-designed resistive-type HTS FCL is defined as a component in PSCADIEMTDC simulations from which the proposed method will be used to optimize the selective parameters of the SFCL. The above requires the need of advanced numerical techniques for simulation studies by PSCAD on a sample distribution system for determining a global optimum HIS FCL, by considering individual parameters and accounting for the constraints, which is the main motivation for initiating this paper. [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 presents an idea for a thermosiphon that uniquely implements two integrated evaporators to cool two HTS (High Temperature Superconductor) bulk sets in different locations, simultaneously. A so-called double-evaporator thermosiphon was designed, fabricated and tested using nitrogen as the working fluid under sub-atmospheric pressure conditions. The operating target temperature was approximately 65 K. To confirm the feasibility of the double-evaporator thermosiphon, experiments during the cool down process and steady state operation were extensively conducted on the double-evaporator thermosiphon (Ltot = 1075 mm, d0 = 160 mm). The double-evaporator thermosiphon worked successfully at steady state operation. The results showed that it had a maximum total temperature difference between the condenser and the evaporator of 1.3 K and a temperature difference between the two evaporators of 0.6 K at a heat flow of 87W. This thermosiphon was designed for actual application to a 100 kWh SFES (Superconducting Flywheel Energy Storage) system. The potential impact of superior heat transfer characteristics of the double-evaporator thermosiphon is discussed in the paper. [ABSTRACT FROM AUTHOR]

The magnet for superconducting magnetic energy storage system (SMES) cooled by SRDK-408 cryocooler has been described in this paper. The superconducting magnet consists of 7 double-pancake coils made of Bi-2223 HTS tape with the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is about 1 H. In the paper we report the design and the first measurements results of the magnet. [ABSTRACT FROM AUTHOR]

This paper deals with design and operating test of a novel hybrid FCL. The FCL system consists of a coil, a fast switch and a resistor for bypassing the fault current. The switch is driven by novel non-inductive coil suggested in this paper but an extra driving coil is required for fast switch in existing hybrid FCL. We used two kinds of HTS wire for the coil. The impedance of the coil was negligible in normal operation. But different quench characteristics of HTS wires caused asymmetric current distribution which induced effective magnetic flux in the coil during faults. The switch was opened by repulsive force from this magnetic flux in fast response to the fault. Then, all current were flew through the normal conductive bypass resistor connected in parallel to both the coil and the switch. Electromagnetic analysis of the coil based on finite element method was performed. Also, a small-scale asymmetric non-inductive coil was designed, fabricated and tested. The proposed hybrid FCL system showed fast and efficient current limiting characteristic. [ABSTRACT FROM AUTHOR]

In this paper, we present a simulation process of the melt-texture YBCO high-temperature superconductor (HTS) bulk levitated over the permanent-magnet (PM) guideway, and further experiment also been built to analyze the dynamic behavior of HTS. The relation between suspension force and amplitude of the levitation system under single-degree of freedom vibration environment was investigated, and stiffness was acquired based on the experiment. Besides, equation of motion of the suspension system was presented in this paper, and with an attempt to analyze and predict damping properties of HTS in given dynamic conditions. The obtained simulation results of the suspending motion behavior also prove that high damper on the levitation body could strengthen the levitation system's capacity of resisting the vibration impact. [ABSTRACT FROM AUTHOR]

This paper presents the design and performance results of a pair of conduction-cooled brass current leads for a resistive superconducting fault current limiter (SFCL) system. The 24 kV class SFCL, which has been recently developed by the KEPRILSIS collaboration group in Korea, requires three pairs of conduction-cooled brass current leads operated continuously at 630 A. When the SFCL system is in the fault-mode, the current leads have experienced a 60-Hz fault current of ∼10 kA at 24 kV for 3–5 cycles. In this paper, we present the performance results of the conduction-cooled brass (commercial brass, 10% Zn) leads having a rated current of 667 A operated in a bath of liquid nitrogen. [ABSTRACT FROM AUTHOR]

A 154 kV class high-temperature superconducting (HTS) power cable system is developing in Korea. For insulation design of this cable, the grading method of insulating paper is proposed. The electrical insulation material has been used two kind of laminated polypropylene paper (LPP) that has different thickness. The use of graded insulation gives improved mechanical bending properties of the cable. Also, within a HTS cable technology the terminations are important components. A HTS cable termination is energized with the line-to-ground voltage between the coaxial center and outer surrounding conductors, in the axial direction there is a temperature difference from ambient to about 77 K. For insulation design of this termination, the insulation material of the termination body used glass fiber reinforced plastic (GFRP) and the capacitance-graded method is proposed. Therefore, in order to insulating design of a 154 kV class HTS power cable and termination, this paper will report on the experimental investigations in impulse breakdown and surface flashover characteristics of the insulation materials. Based on these experimental data, the electrical insulation design of a 154 kV class HTS power cable and termination were calculated. [ABSTRACT FROM AUTHOR]

Synchronous reactance is an important parameter of synchronous rotating machine because it affects on the machine output capacity, voltage variation and steady-state stability. The superconducting synchronous rotating machine has very small synchronous reactance about 1/5 of the conventional synchronous machine. This reason comes from the fact that the superconducting rotating machine is air-cored structure. In this paper, it is estimated how much this synchronous reactance has influences on many design parameters of superconducting synchronous machine such as machine volume and weight, efficiency, voltage variation and so on. In the case of a synchronous motor, the power factor can be adjusted according to the excitation voltage. This paper also deals with the effects of power factor on the design parameters and the performance of a HTS (High-temperature Superconducting) synchronous motor. This kind of analysis was used to design 1 MW class HTS motor. [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]

A superconducting motor consisting of high temperature superconducting (HTS) rotor and air-core stator is under development in Korea Electrotechnology Research Institute. HTS motor was designed for having the rated power of 100 HP at 1800 rpm. HTS field winding is composed of sixteen HTS race track shaped coils wound with stainless steel-reinforced Bi-2223 tape conductor by react and wind fabrication method. Nomex paper was used for electrical insulation. Each of four field coil assemblies was constructed with four double pancake sub-coils, mechanically stacked and electrically connected in series. Four field coil assemblies were fixed on an aluminum support structure to make effective heat transfer. Voltage terminals were attached to both ends of joints to measure joint resistances. HTS field winding was tested at 77 K, and the Joule heats generated at all the joints was calculated. In this paper, design, construction and testing of HTS field winding, Joule heat generated by the joints, and operating current were discussed. [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]

This paper describes an effective method to calculate hysteresis loss of high-temperature superconducting (HTS) bulk material under time varying magnetic field. In the proposed method, the inner product of current and electric field in a HTS bulk is integrated to calculate hysteresis loss. To consider the nonlinear relation between the current and the electric field of HTS bulk material, critical state model and iteration method are adopted. According to the critical state model, if different types of time varying magnetic field are applied, the current distribution in a HTS bulk is affected not by applied field types but by peak-to-peak field values on the assumption of same critical current density regardless of different field types. This is the basic idea to compute hysteresis loss more effectively. This paper shows how to reduce total calculation time using the suggested method. To verify the validity of the suggested method, numerical results are compared with experimentally measured ones. [ABSTRACT FROM AUTHOR]

Electrical motors need a spatial variation of the flux density created by their inductors to make torque. We propose to achieve this angular repartition of the induction with bulk high temperature superconducting plates and two low temperature superconducting solenoids. These solenoids have the same axis and are fed with opposite currents in order to create a radial magnetic induction. Four superconducting plates placed on the cylindrical surface, situated on the same axis and having the same radius as the solenoids, concentrate the magnetic field. This device provides a spatial variation of the flux density, and can be considered as an inductor for a synchronous motor with eight poles. This paper presents the experimental study of our prototype at 4.2 K. We compare the experimental results with calculation. Ten hall probes permit us to reconstitute the angular variation of the flux density. The paper shows the feasibility of this new kind of superconducting inductor. [ABSTRACT FROM AUTHOR]

A further development of the high temperature superconducting (HTS) mini power plant (MPP) concept designed earlier by one of the authors is presented in the paper. HTS fault current limiters (FCL) will be inserted at the terminals of the synchronous generator. Joint operation of HTS generators (including fully superconducting generators) and HTS FCL's provide additional benefits viz. a significant increase of the generator's unit power rating as well as of its dynamic stability, shown in the paper. A three-phase inductive HTS FCL designed and built for the protection of a generator is made up of three one-phase units, each containing YBCO rings as secondary "windings." A new design idea was applied for the primary winding to further reduce the leakage reactance of the FCL resulting in low reactive power consumption. Simulations of the electromagnetic processes in the HTS FCL are shown. Theoretical studies on the joint operation of a fully superconducting generator and an HTS FCL are presented. [ABSTRACT FROM AUTHOR]

Superconducting magnet systems operated at cryogenic temperature require high temperature superconducting (HTS) current leads to reduce the heat intrusion from the power supply at room temperature. However, some kinds of accidents, such as cryogenic failure, can cause a quench in the HTS current lead. Since the current conducting through the HTS current lead is very large, the quench in a HTS part can lead to a severe device failure. Therefore a study of a protection method for the HTS current lead is important. Generally, the HTS part of current lead used in large scale magnet systems has multiple separated HTS tape strands. They are electrically not connected or poorly connected. Therefore the quench in one strand affects other strands in current lead by applying additional loads for the other parts of the HTS current lead. In this paper, a strand-to-strand bridging method with HTS tapes is proposed as a quench protection method. Small scale HTS current leads with 2G HTS tapes and the suggested bridging method have been fabricated and tested. [ABSTRACT FROM PUBLISHER]

A series of pancake coils using several kilometers of second generation (2G) (RE)BCO conductor has been fabricated as a part of a R&D program to build a large aperture high field solenoid for energy storage application. This paper discusses the preparation of double pancake coils and the test results at 77 K before assembling the final magnet. These tests played an important role in assuring: the quality of conductors, coil winding and assembly, and integrity of splices within the coils. [ABSTRACT FROM PUBLISHER]

In this paper, the high temperature superconductor (HTS) winding and multitoothed structure are newly incorporated into the doubly salient (DS) and flux-switching (FS) machines, leading to create two new magnetless machines, namely the HTS-based multitoothed switched reluctance (HTS-MSR) and HTS-based multitoothed flux-switching (HTS-MFS) machines. Consequently, the design equations of the three machines, namely the MSR, HTS-MSR, and HTS-MFS, are formulated. The corresponding performances are analyzed by using the time-stepping finite element method (TS-FEM). By utilizing both torque-producing zones, the two HTS-based machines can achieve better performances than the MSR one. Moreover, the HTS-MFS can offer higher torque density than the HTS-MSR, but associated with larger torque ripple. [ABSTRACT FROM PUBLISHER]

ASIPP will supply for ITER all the current leads. There are three types of high temperature superconducting (HTS) current leads designed to carry 68 kA, 55 kA, or 10 kA to the ITER magnets. Different from the trial leads manufactured and tested in Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP), some critical technologies were qualified before the manufacturing of the ITER leads could commence, including: 1) welding, brazing, and soldering qualification; 2) fin type heat exchanger (HEX) with tight assembly tolerance; 3) low temperature superconducting (LTS) linker with cables soldered to the 5 K copper terminal; 4) instrumentation mock-up for the temperature and voltage test. In this paper, the outcome of these qualification activities will be reported together with the plans for the series production planning and development. [ABSTRACT FROM PUBLISHER]

A heat-shrink tube insulation for second-generation high-temperature superconducting (2G HTS) coils is studied experimentally in this paper. The insulation can be used to prevent the delamination of 2G HTS due to epoxy impregnation. According to the experiment results, the insulated coil shows no degradation before and after the epoxy impregnation. To validate the performance of 2G HTS coils with the heat-shrink insulation, we measured the transport loss, magnetization loss and total loss of a 2G HTS coil. The study demonstrates the feasibility of the heat-shrink tube insulation method for electrical applications. [ABSTRACT FROM PUBLISHER]

This paper deals with the latest design of an all High Temperature Superconductor (HTS) insert for our 1.3 GHz NMR program. Due to a loss of our original 600 MHz HTS insert, the entire program was revised, and upon further examination of the options available for the HTS insert, which included not only conductor material properties, but also new winding technologies recently developed here at the FBML, it has finally been decided to build an 800 MHz (H800) insert purely based in SuperPower YBCO conductor. The new H800 will still be comprised of nested stacks of double-pancake coils and will run in the background of a 500 MHz LTS NMR magnet already available at FBML. We present here electromagnetic and mechanical details of the H800 design, winding technique employed, and testing of individual coils. [ABSTRACT FROM PUBLISHER]

The Procurement of Feeder system in Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) for The International Thermonuclear Experimental Reactor (ITER) Tokamak device has been carrying out after the signature of Procurement Arrangement in October 2011. The relevant main tasks in 2012 and 2013 are the qualification of some key subcomponents, including high temperature superconducting current leads (HTS-CL), superconducting joints, 80-K thermal shield (TS), vacuum barrier, in-cryostat feeder, cold mass support, etc. The production of manufacturing drawings, preparation of manufacturing plan, manufacture and qualification of tooling, and qualification of subcomponents are all involved in this phase. This paper describes the progress made by ASIPP and some sub-contractors for the feeder's qualification work. [ABSTRACT FROM PUBLISHER]

A potential future muon collider requires high field solenoids (> 30 T) for the final cooling stage; the Magnet Division at Brookhaven National Laboratory is undertaking the task of demonstrating feasibility using high-temperature superconductors (HTS). The aim is to construct an all-HTS dual-coil system capable of delivering more than 20 T. Recently, a new record for an all-HTS solenoid has been established with a field of 15 T on-axis. In coil tests, it was noticed that during a fast energy extraction, the current in the solenoids decays faster in comparison to the expected exponential decay. This paper describes the effect and shows how it can be simulated using commercial finite element code. The faster current decay helps to lower the integral current density squared with time by about 10% and is therefore beneficial for quench protection. [ABSTRACT FROM PUBLISHER]

In this paper, the use of magnetic materials to divert flux in high-temperature superconductor superconducting coils and reduce transport ac loss is investigated. This particular technique is preferred over other techniques, such as striation, Roebel transposition, and twisted wires because it does not require modification to the conductor itself, which can be detrimental to the properties of the superconductor. The technique can also be implemented for existing coils. The analysis is carried out using a coil model based on the \bf H formulation and implemented in comsol multiphysics. Both weakly and strongly magnetic materials are investigated, and it is shown that the use of such materials can divert flux and achieve a reduction in transport ac loss, which, in some cases, is quite significant. This analysis acts to provide a foundation for further optimization and experimental work in the future. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a new high-temperature superconducting (HTS) coil with shorter HTS tape length. In general, the critical current and n-value of an HTS tape depend on the applied magnetic field magnitudes and angles. Therefore, we derived fitting equations for the critical current and n-value in terms of these parameters obtained from the measurements of a Bi-2223/Ag tape at 77 K. Relatively large electric fields were generated at the coil edges because of the large magnetic fields and angles. This phenomenon prevents improvement of transport-current performance of an HTS coil. To solve this problem, we created a new HTS coil with edge vacancies and central separation. Analysis results revealed that the coil critical current increased significantly. Furthermore, we found an optimum coil shape that results in the improvement of the central magnetic field and stored energy by 33% and 99.5%, respectively, compared with those of the normal coil, irrespective of the reduction in the total HTS tape length owing to edge vacancies. [ABSTRACT FROM PUBLISHER]

In this paper, we derive integral equations for radially and polygonally arranged high-temperature superconductor thin tapes, and we solve them by finite-element method. The superconductor is modeled with a nonlinear power law, which allows the possibility of considering the dependence of the parameters on the magnetic field or the position. The ac losses are computed for a variety of geometrical configurations and for various values of the transport current. Differences with respect to existing analytical models, which are developed in the framework of the critical state model and only for certain values of the transport current, are pointed out. [ABSTRACT FROM PUBLISHER]

This paper presents a high-temperature superconducting (HTS) planar balun. The balun exhibits an excellent amplitude and phase balance performance. The balun was fabricated using double-sided HTS YBCO films on a 0.5-mm-thick 3-in \LaAlO3 substrate. The balun demonstrates a wideband operation and a low insertion loss. The center frequency of the balun is 1.25 GHz. The return loss bandwidth of -18 dB is 1.02 GHz (the fractional bandwidth is 82%). The phase imbalance is less than 7^\circ. The amplitude imbalance is less than 0.7 dB, and the insertion loss is less than 0.31 dB over 0.69–1.77 GHz. [ABSTRACT FROM PUBLISHER]

We have developed a magnetic levitation system using a magnetic shielding effect of high temperature superconducting bulks. We have already succeeded to demonstrate principle of the levitation. In the paper, we tried to increase the levitation force. Firstly, when a ferromagnetic plate was put underside of a permanent magnet, the levitation force increased. And when the underside ferromagnetic plate was protruded from the magnet, the levitation force effectively increased furthermore. Lastly, the levitation force exceeded vehicle weight and the stable levitation became possible. [ABSTRACT FROM PUBLISHER]

This paper presents the design of an AC loss experiment using nitrogen boil-off method. This experiment is aimed at exploring the AC loss of HTS double race-track coils which will be installed on the rotor of a wind turbine generator. The operating environment is simulated by designing a cryostat with rotating magnetic field windings. Apart from the fact that the alternating magnetic field causes most of AC loss on the HTS coils, we also believe that the DC background field would be another important factor causing AC loss if the HTS coil is experiencing by both alternating magnetic field in the perpendicular direction and DC background field in the parallel direction. In order to perform the boil-off measurement, we present the method to estimate the heat leakage in the cryostat which might cause errors to the measurement . [ABSTRACT FROM PUBLISHER]

A 1-km, cold dielectric, high-Tc superconducting (HTS) power cable is being planned in China. The rated voltage and current are 110 kV and 2 kA, respectively. The termination, which connects the superconducting cable conductors at cryogenic temperature to a power transmission line at room temperature and an external cooling system at ground potential, is one of the crucial parts of the superconducting cable system. In this paper, such a termination is designed, including the current lead, the electrical insulation, the condenser cone and the SC-NC joint. [ABSTRACT FROM PUBLISHER]

The current margin of a jointed model cable of the 275 kV class high-temperature superconductor (HTS) power cable was measured under fault condition. The cable-to-cable joint is necessary to connect long continuous sections of the power cable. At the joint the superconductor is prone to degradation due to an excessive temperature rise caused by the current passing through normal conducting zones of the joint. The jointed, and for the comparison the joint-less cables were subjected to a short-circuited fault current of 63 kA rms for 0.6 s. In the results, the allowable current margins were about the same for both model cables. The jointed cable degraded at the joint area from the result of the magneto-optical (MO) image. The numerical simulations were performed to clarify current distribution and temperature rise at the cable joint area. The temperature rise as a function of the joint gap was also calculated. The experimental and simulation results were showed in this paper. [ABSTRACT FROM PUBLISHER]

The key to being able to operate the superconducting solenoids in the Muon Ionization Cooling Experiment (MICE) using cryocoolers running at around 4.2 K is the application of high temperature superconducting (HTS) leads. Because the MICE magnets are not shielded, all of them will have a stray magnetic field in the region where the coolers and the HTS leads are located. The behavior of the HTS leads depends strongly on the HTS material used for the leads, the magnetic field and their warm end temperature. A pair of binary leads consisting of copper leads and HTS leads made from oriented multiple strands of BSCCO wires will be used for electrical transfer of the MICE coupling magnet for the purpose of reducing the heat leak through the leads to 4.2 K region. This paper mainly discusses the detailed design of the HTS leads and their cooling. Protection for the HTS leads during a power failure is discussed as well. [ABSTRACT FROM PUBLISHER]

In this paper, a new linear stator permanent magnet (PM) vernier high-temperature superconductor (HTS) machine is proposed for wave energy conversion. The machine adopts a double-sided design and inner-translator arrangement where the stator consists of two plane iron cores with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of the stator teeth. While the translator is designed as an iron core with salient teeth on the two sides, the HTS bulks are inset between every two adjacent salient teeth to shield the flux leakage, thus improving the power density of the machine. Based on using the finite element analysis, the characteristics and performances of the proposed machine are assessed. Also, the proposed machine is quantitatively compared with the existing linear stator PM vernier machine. Hence, it validates that its performance, especially the power density, can be improved significantly. [ABSTRACT FROM PUBLISHER]

In this paper we extend the recently developed CtFD strategy for the analysis of the thermal-hydraulics of a meander flow type heat exchanger, validated against the Wendelstein7-X (W7-X) High Temperature Superconductor (HTS) current lead prototype experiment, to the case of a heat exchanger for a 68 kA HTS current lead. We aim to assess the optimized operative conditions and the influence of different geometrical configurations on the performance of the heat exchanger. [ABSTRACT FROM PUBLISHER]

This paper aims to study the feasibility of improving pulsed current output by using High temperature superconducting (HTS) air-core transformer. Based on the theoretical analysis, the simulations are done. Results of the simulations indicate that the HTS air-core pulse transformer can magnify the output current magnitude and accelerate the velocity of discharge. However, when a series of inductor modules use the same one HTS air-core transformer, the residual current may influence the discharging waveform. To eliminate residual current, self-coupling discharging model is proposed. The simulated and experimental results illustrate that a self-coupling model can eliminate the residual current effectively. The results of this analysis contribute to the research of superconducting inductor pulsed current output. [ABSTRACT FROM PUBLISHER]

Now that ITER is entering construction, many of its systems are in the final stages of design and analysis. Among them the 31 feeders, which will be supplied in-kind by the Chinese ITER partner. The feeders supply the electrical power and cryogens through the warm-cold barrier to the ITER superconducting magnet systems. They are complex systems with their independent cryostats and thermal shields, densely packed with many components, such as the current feeds, the cryogenic valves and High-Voltage (HV) instrumentation hardware. Some of the feeder components are particularly critical and have been designed with great care. Among them the High-Temperature Superconductor (HTS) current leads, designed for unprecedented currents, the 30 kV class, Paschen-hard HV insulation and the bus bar support system, designed to react the multi-ton Lorentz-forces from the bus bars at minimal heat load. This paper discusses the design challenges for these (and other) key components of the ITER magnet feeders. [ABSTRACT FROM PUBLISHER]

Korea Electric Power Corporation (KEPCO) has a great interest on the application of HTS cable to its network to relieve power congestion and enhance the reliability of the power system. Down through the years from 2005 to 2010, the 22.9 kV, 50 MVA HTS cable has been demonstrated by field test, showing affirmative results. With the financial support of Ministry of Knowledge and Economy (MKE), the new project to install and operate the HTS cable in electrical network of Korea was launched in 2008. An HTS cable with the 22.9 kV, 50 MVA, and 410 m length was installed in the KECPO grid in the end of 2010. After the integration of the HTS cable system, the commissioning items of the DC withstand voltage test, DC critical current test, and heat loss measurements were conducted in accordance with the Korean industrial standard, and self-defined specifications. The HTS cable was energized on the 154 kV Icheon substation of KEPCO on August 19th, 2011. The details of the project description, onsite installation, and commissioning tests are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents the optimization study of the field winding structure of the 20 MW-class HTS motor for the electric ship propulsion based on the minimization of the flux flow loss. The examples of the optimized shape of the HTS field pole coils obtained by the numerical analysis are presented. By optimizing the cross section of the field pole coil, it is found that the magnetic field perpendicular to the tape surface in the optimized shape coil significantly decreases compared with that in the rectangular shape base coil. As the results of the reduction of the perpendicular magnetic field, it is shown that the flux flow loss remarkably decreases. It is also pointed that the necessary length of the HTS tape for the optimized shape coil increases. [ABSTRACT FROM PUBLISHER]

This paper deals with design and operating tests of prototype hybrid superconducting fault current limiter (SFCL) which is series connected non-inductive solenoid resistive coil and asymmetric non-inductively wound coils. The role of resistive SFCL is for reducing the fault current in the first swing. Moreover, resistive SFCL can reduce a load of dielectric strength in hybrid SFCL. Two kinds of high temperature superconductor (HTS) wires were used to fabricate asymmetric HTS coil. These HTS wires had different quench characteristics such as different critical current and n-value. Unbalanced current distribution between two HTS wires in the asymmetric HTS coil during the fault should occur. Thus, the asymmetric HTS coil generates impedance and repulsive force from magnetic flux. The finite element method was performed to calculate maximum repulsive force. From experimental tests and FEM simulation results, proper combination of HTS wires and configuration of asymmetric HTS coil with fast switch were determined to increase maximum repulsive force. Also, the prototype hybrid SFCL with fast switch was fabricated and performed. [ABSTRACT FROM PUBLISHER]

In fabrication of a compact NMR (Nuclear Magnetic Resonance) magnet which consists of a stacked HTS (High Temperature Superconducting) bulk annuli, generally there are three key issues: spatial homogeneity, temporal stability, strength of trapped magnetic fields. This paper presents a study on the effects of axial gap length between stacked HTS bulks on the three key issues of a bulk HTS magnet for compact HTS NMR applications. The HTS bulk magnet of which the ID and OD are 20 and 60 mm respectively has a 50 and 80 mm heights depending on the axial gap lengths between HTS bulks. The gap length between each HTS bulk varied from 0 mm to 10 mm and were used as parameters to optimize, analytically as well as experimentally, the overall field homogeneity of the HTS bulk magnet. The optimized axial gap length was obtained by analytical results, and the better magnetic field homogeneity and temporal stability of trapped magnetic field were achieved by lower magnetization field. The improved spatial homogeneity and strength of generated magnetic field by a new compact NMR magnet will be presented. [ABSTRACT FROM PUBLISHER]

The Procurement of the feeder system for The International Thermonuclear Experimental Reactor (ITER) tokamak device started in ASIPP (China) in 2006. The relevant tasks of structural design and analysis have now come to an end, but the R&D activities started in 2009 for critical feeder components and key technology are still ongoing. Following the signature of the Procurement Arrangement between China and the ITER Organization (IO) in 2010, a great number of R&D tasks have been launched with the purpose of testing and verifying the original design, leading to design changes and optimizations. This paper mainly discusses the progress of the feeder design and R&D activities; it also presents some test results. [ABSTRACT FROM PUBLISHER]

This paper reports a study of two HTS racetrack coils wound with GdBCO coated conductors, one without turn-to-turn insulation and the other with Nomex insulation. The coils were characterized by charge-discharge, over-current, and sudden discharge tests. Thermal and electrical characteristics of the GdBCO racetrack coil without insulation outperformed the insulated one. The test results confirmed that although the coil without insulation has a slow charging/discharging time constant, the no-insulation winding technique may enable a compact and protection-free racetrack-typed coil with enhanced mechanical integrity as well as better thermal and electrical stabilities. [ABSTRACT FROM PUBLISHER]

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contact transportation device which moves freely in space. In our previous work, the unstable movement characteristics of HTS bulk were observed under DC operation, and the AC control system was proposed in order to solve these problems. In this paper, the horizontal movement and the field decay characteristics as a function of the gap length between electromagnet and HTS bulk and the frequency of driving current were investigated experimentally. [ABSTRACT FROM PUBLISHER]

This paper quantitatively compares three types of double-stator flux-modulation permanent-magnet (PM) machines, namely the vernier machine, vernier machine with HTS bulks, and magnetic-geared machine. Due to adopting the double-stator topology, these PM machines achieve the higher energy transmission and power conversion than the single-stator counterparts. Also, the design for the proposed machines are to respectively use the flux-modulation pole, HTS bulk and the flux-modulation ring for modulating the low speed rotating field of the PM rotor and the high speed rotating field of the armature windings, hence obtaining the gear effect for low speed operation. It should be noted that by using the HTS bulks can not only efficiently improve the flux modulation effect of the vernier machine, but also greatly reduce the machine flux leakage. By using the finite-element-method, their performances are compared, hence verifying the validity of the machine design. [ABSTRACT FROM PUBLISHER]