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Applied Superconductivity, IEEE Transactions on

Issue 5 • Date Oct. 2011

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Displaying Results 1 - 18 of 18
  • [Front cover]

    Page(s): C1
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  • IEEE Transactions on Applied Superconductivity publication information

    Page(s): C2
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  • Table of contents

    Page(s): 3493
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  • Optimization of the Stress Distribution of Helical Coils With a Cable-in-Conduit Configuration

    Page(s): 3494 - 3500
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (641 KB) |  | HTML iconHTML  

    Virial-limit coils for application to magnetic confinement nuclear fusion devices are hybrid helical coils that level electromagnetic stresses. In past research, a possibility that a large bending stress is caused in helical coils made of a cable-in-conduit configuration (CICC) was pointed out. In this paper, we analytically evaluated the stresses of helical coils made of CICC by modeling them as springs and calculated a detailed stress distribution by finite-element method (FEM) analysis. FEM results show that the bending and torsional stresses, which are ten times or more as large as the membrane stress, are caused. These stresses are caused by the moment of electromagnetic forces, which can be explained by modeling helical coils as coil springs. We propose a helical coil that lessens the moment and confirms the effect of the reduced moment, and the coil under this optimal condition of moment reduction is termed a moment-free coil. View full abstract»

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  • Numerical Study of Quench Protection Schemes for a  \hbox {MgB}_{2} Superconducting Magnet

    Page(s): 3501 - 3508
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    Thermal stability and protection in the event of quench are key issues in the design of superconducting magnets. Quench development and propagation strongly depend on the conductor characteristics and the magnet configuration. An adequate quench protection method must maintain both the peak temperature and the peak voltage during the event within acceptable limits. This paper presents quench modeling and evaluation of candidate protection schemes for a superconducting coil based on a magnesium diboride (MgB2) wire, designed for use in a new cryogen-free magnetic resonance imaging scanner. The wire properties are different, and the current density is significantly higher from those previously reported. In contrast to previous studies, it is concluded that the coil cannot be considered self-protecting and that protection using external resistance provides a practically acceptable solution. View full abstract»

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  • Numerical Field Calculation in Support of the Hardware Commissioning of the LHC

    Page(s): 3509 - 3513
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (391 KB) |  | HTML iconHTML  

    The hardware commissioning of the Large Hadron Collider required the testing and the qualification of the cryogenic and vacuum system, as well as the electrical systems for the powering of more than 10 000 superconducting magnets. Non-conformities had to be resolved within a tight schedule. In this paper, we focus on the role that electromagnetic-field computation has played during hardware commissioning in terms of the analysis of a magnet quench and electromagnetic-force calculations in busbars and splices, as well as field-quality prediction for the optimization of powering cycles. View full abstract»

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  • Viable Inductive Superconducting Fault-Current Limiters Using Autotransformer-Based Hybrid Schemes

    Page(s): 3514 - 3522
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    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. View full abstract»

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  • A Homopolar HTSG Topology for Large Direct-Drive Wind Turbines

    Page(s): 3523 - 3531
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    For offshore wind energy, there is a trend toward larger wind turbines. The increased mass of a power-takeoff system increases the installation cost of the turbine. Direct-drive superconducting generators have the potential to reduce the installation cost of wind turbines. For a successful entry to the offshore-wind-energy market, a high-temperature superconducting generator should be as reliable as conventional generators. It is proposed that a stationary superconducting direct-current-field winding may increase the reliability of the generator. An axial-flux homopolar generator topology is proposed to be used in low-speed high-torque applications. The topology is modified by using two superconducting field windings to obtain a bipolar flux-density distribution for higher power density. Different core types and dimensions were examined to find the most suitable design, and a conceptual design of a 6-MW 12-r/min generator is presented. View full abstract»

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  • Experimental and Theoretical Levitation Forces in a Superconducting Bearing for a Real-Scale Maglev System

    Page(s): 3532 - 3540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1242 KB) |  | HTML iconHTML  

    A numerical model based on the critical-state approximation and on a magnetic-energy minimization procedure is presented to simulate the levitation of a system composed of two isolated infinitely long superconductors levitating over permanent-magnet guideways. Three different sets of magnetic guideways are simulated and compared with experimental tests of a linear superconducting magnetic bearing for a prototype of a real magnetic levitation vehicle. In spite of the complexity of the permanent-magnet guideway design, the model serves as a first approach to calculate the vertical levitation force of these superconducting bearings. The measured and calculated force results validate the model applied to study these systems, in addition to some limitations caused by simplifications considered in the theoretical model. View full abstract»

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  • Numerical Study of Josephson Junction Qubits With an Unharmonic Current–Phase Relation

    Page(s): 3541 - 3547
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    This paper numerically analyzes the influence of second harmonics on the characteristics of Josephson junction quantum bits (qubits). It is shown that the splitting of energy states of phase qubits is sensitive to energy scale and unharmonicity parameters. On the other hand, for charge qubits, the expectation value of the Cooper-pair number is not affected by the inclusion of unharmonicity parameters, whereas the expectation value of the superconducting current is strongly influenced by energy scale and unharmonicity parameters. The numerical results seem to present the importance of second harmonics in the realization of superconducting qubits. View full abstract»

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  • Optimization of a Linear Superconducting Levitation System

    Page(s): 3548 - 3554
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    The Laboratory for Applied Superconductivity of the Federal University of Rio de Janeiro (LASUP) has been developing a superconducting magnetic levitation urban train named MagLev-Cobra. It is a kind of light rail vehicle where the conventional wheel-rail track is substituted by a rail of Ne-Fe-B magnets and carbon steel interacting with superconductor bulks installed in the vehicle to promote levitation. The main cost of this levitation system is the magnetic rail. Therefore, any improvement in the shape and configuration of magnets and iron has a significant budgetary impact. In this paper, the optimizations carried out with the feasible direction interior point algorithm, extensive search, and genetic algorithm of magnetic rails are presented. The objective is to find the geometry that minimizes the total cost, for a given levitation force, considering some practical restrictions. The levitation force restriction is calculated using a finite-element method. During the optimization process, the superconductor null permeability model is used. Finally, the results are checked with the Bean model and verified experimentally. Measurements of the levitation force and the field mapped over the magnetic rails are presented. Significant reduction of soft and hard ferromagnetic materials was reached. View full abstract»

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  • Slip–Stick Mechanism in Training the Superconducting Magnets in the Large Hadron Collider

    Page(s): 3555 - 3560
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    Superconducting magnets can exhibit training quenches during successive powering to reaching nominal performance. The slip-stick motion of the conductors is considered to be one of the mechanisms of training. In this paper, we present a simple quantitative model where the training is described as a discrete dynamical system matching the equilibrium between the energy margin of the superconducting cable and the frictional energy released during the conductor motion. The model can be explicitly solved in the linearized case, showing that the short sample limit is reached via a power law. Training phenomena have a large random component. A large set of data of the large hadron collider magnet tests is postprocessed according to previously defined methods to extract an average training curve for dipoles and quadrupoles. These curves show the asymptotic power law predicted by the model. The curves are then fit through the model, which has two free parameters. The model shows good agreement over a large range, but it fails to describe the very initial part of the training. View full abstract»

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  • Reliability Evaluation of Distribution Network With DG Considering the Reliability of Protective Devices Affected by SFCL

    Page(s): 3561 - 3569
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (710 KB) |  | HTML iconHTML  

    This paper proposes a reliability model for a superconducting fault current limiter (SFCL), which is a new alternative in limiting the fault current recently increasing in a network. An evaluation technique for distribution reliability that uses the improved failure rate of all protective devices in a network, depending on the location of the SFCL, is also proposed. As a result, it is expected that the SFCL makes the reliability of adjacent equipment on an existing network improve, and these changes are analyzed. In addition, in order to apply the effect of the intermittent output of renewable-energy sources, distribution reliability indices were redefined in this paper. Case studies verify that the SFCL is effective in reducing fault currents and improving distribution reliability. These effects are analyzed with respect to the location of the SFCL in a case study system. View full abstract»

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    Page(s): 3570
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    Page(s): 3571
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    Page(s): 3572
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  • IEEE Transactions on Applied Superconductivity upcoming special conference issues

    Page(s): C3
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  • IEEE Transactions on Applied Superconductivity Information for authors

    Page(s): C4
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Aims & Scope

IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

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Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde