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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Aug. 2010

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Displaying Results 1 - 17 of 17
  • [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): 2213
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  • Study of High-Tc Superconducting Bulk Moving With Different Speeds in Applied Magnetic Fields

    Page(s): 2214 - 2218
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB) |  | HTML iconHTML  

    The force-speed relationship of a bulk YBCO moving above a permanent magnetic guideway was studied. The experiments show that the levitation forces at the lowest position Fmax increase with the increment of descending speed and tend to approach a certain levitation force FS.max. Calculations based on a simplified superconducting ring and flux flow model show that the force variations can be ascribed to the resistive electric field produced by flux motion. Further calculation reveals that, by increasing the descending speed, the thermo-dissipation inside the superconducting ring immediately after the descending process exponentially declines, approaching zero while the speed approaches infinity, and Fmax reaches FS.max. Therefore, the thermo-dissipation inside the bulk YBCO can be defined as a parameter for evaluating levitation force losses. Those results might be useful in pragmatic design of high-Tc superconducting levitation devices and magnetization of type-II superconductors. View full abstract»

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  • 3-D Modeling of High- T_{c} Superconductor for Magnetic Levitation/Suspension Application—Part I: Introduction to the Method

    Page(s): 2219 - 2227
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    A magnetic levitation technique with high-Tc superconductor (HTS) has received significant interest for a wide range of applications after its discovery due to its unique inherent stability, which gives a fundamental significance to evaluate the HTS magnetic levitation in both experiment and calculation. To numerically investigate the HTS magnetic levitation, a 3-D model describing the electromagnetic property of the HTS, including its anisotropic behavior, was established by incorporating the current vector potential and Helmholtz's theorem. In addition to the commonly considered nonlinear E-J characteristic in the reported calculation, we introduce an elliptical model to formulate the angular dependence of the critical current density Jc resulting from the anisotropic behavior of the HTS. To numerically resolve the governing equations of the 3-D model, Galerkin's finite-element method and the Crank-Nicolson-θ method were employed to discretize the governing equations in space and time domains, respectively. The obtained algebraic equations were firstly linearized by the Newton-Raphson method, and then an extended format of the incomplete Cholesky-conjugate gradient method was applied to solve the linear algebraic equations. The 3-D model was implemented by a self-written numerical program based on a VC++ platform to calculate the magnetic force of a bulk HTS exposed to applied field generated by a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. In this paper, we present the numerical results of the levitation force of a moving bulk HTS above the PMG with different mesh densities and number of time steps. This presents a preliminary validation of the 3-D model proposed in this paper. View full abstract»

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  • 3-D Modeling of High- T_{c} Superconductor for Magnetic Levitation/Suspension Application—Part II: Validation With Experiment

    Page(s): 2228 - 2234
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (954 KB) |  | HTML iconHTML  

    In this paper, the 3-D model proposed in Part I of this study is verified in detail on the basis of a levitation/suspension system composed of a rectangular single-domain Y-Ba-Cu-O and a cylindrical Nd-Fe-B magnet or a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. The magnetic forces along the vertical direction perpendicular or the transverse direction parallel to the surface of the PMG (or magnet) were calculated and compared well with the measured data under vertical and transverse displacements. The computed results of the induced current distribution within the Y-Ba-Cu-O domain, as well as the magnetic field profiles in the Y-Ba-Cu-O and its vicinal region, were also presented and discussed. View full abstract»

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  • Design and Optimization of Superconducting Magnet System for 42.0-GHz Gyrotron

    Page(s): 2235 - 2242
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB) |  | HTML iconHTML  

    In the framework of the Department of Science and Technology (DST), Government of India, a 42.2-GHz 200-kW continuous-wave/long-pulse gyrotron is envisaged to be indigenously developed. This gyrotron shall employ superconducting magnets at the interaction region and warm coils for the gun and collector region. The Institute for Plasma Research is responsible for the overall design and fabrication of the magnet system along with the required housing cryostat and auxiliary support system. The design of the appropriate magnet system is currently under progress in accordance with gyrotron physics and engineering considerations. This requires a highly homogeneous spatial field profile as well as a very steep gradient as per the compression and velocity ratios between the emission and resonator regions. These aspects demand a very precise winding of the magnets as well as the collinearity of the magnetic axis with that of the beam axis. Several technological aspects, such as accurately designing and positioning of the magnet system in space, to optimize the required field profile have been taken up in the run up to realize a highly homogeneous and stable magnet system. Different design criteria for the theoretical optimization of magnet parameters and their spatial arrangement such that the required axial magnetic field profile can be achieved have been taken up. In addition, finite-element analysis (FEA) of the optimized magnet parameter is done, and the magnetic field profile is compared with the theory. The detailed design of the guiding magnet system, the optimization of coil parameters, and the FEA simulation for the validation of the optimized parameters are presented in this paper. View full abstract»

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  • Magnetization of Bulk Superconductors Using Thermally Actuated Magnetic Waves

    Page(s): 2243 - 2247
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (988 KB) |  | HTML iconHTML  

    A novel technique is proposed to magnetize bulk superconductors, which has the potential to build up strong superconducting magnets. Instead of conventionally using strong magnetic pulses, periodical magnetic waves with strength as low as that of rare-earth magnets are applied. These magnetic waves travel from the periphery to the center of a bulk superconductor and become trapped little by little. In this way, bulk superconductors can gradually be magnetized. To generate these magnetic waves, a thermally actuated magnet was developed, which is constructed by a heating/cooling switch system, a rare-earth bulk magnet, and a Gadolinium (Gd) bulk. The heating/cooling switch system controls the temperature of the Gd bulk, which, along with the rare-earth magnet underneath, can transform thermal signals into magnetic waves. The modeling results of the thermally actuated magnet show that periodical magnetic waves can effectively be generated by applying heating and cooling pulses in turn. A YBCO bulk was tested in liquid nitrogen under the magnetic waves, and a notable accumulation of magnetic flux density was observed. View full abstract»

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  • Scaling Solution and n Dependence of the Eddy-Current Distribution in a Flat Superconductor

    Page(s): 2248 - 2254
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    In this paper, we propose an approximate analytical solution of the problem of nonlinear diffusion of the current density in a high-temperature superconducting plate with current transport. It is obtained by the technique of self-similar solution. The construction of this solution highlights a characteristic time of penetration Tp whose limit for large n is the model of Bean. We compare our solution to the ones obtained using COMSOL multiphysics. We study the influence of variation of the magnetic induction on time penetration and the influence of the n factor on time penetration. View full abstract»

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  • Superconducting Fault Current Limiter Application for Reduction of the Transformer Inrush Current: A Decision Scheme of the Optimal Insertion Resistance

    Page(s): 2255 - 2264
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1095 KB) |  | HTML iconHTML  

    A conventional superconducting fault current limiter (SFCL) is usually only connected to a power system for fault current limitation. The study described in this paper, however, attempts to use the hybrid SFCL application to reduce the transformer inrush current. To accomplish this, this paper first suggests the concepts to expand the scope of the SFCL application in the power system. The power system operator should first determine the proper amount of current-limiting resistance (CLR) of the hybrid SFCL. Therefore, this paper suggests a decision scheme of the optimal insertion resistance in an SFCL application to reduce the transformer inrush current. This scheme and the SFCL model are implemented using the electromagnetic transient program (EMTP). We determine the optimal CLR by EMTP simulation, and this value is applied to model the SFCL by the EMTP. The simulation results show the validity and effectiveness of the suggested scheme and the ability of the SFCL to reduce the inrush current. View full abstract»

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  • The Design of Miniaturized Superconducting Filters With the Reflected Group Delay Method

    Page(s): 2265 - 2271
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    The reflected group delay method can be used to design higher-order superconducting filters. A correction factor is introduced to ensure that the reflected group delay response is symmetric about the center frequency. The method is demonstrated through the design of an eight-pole lumped-element filter using a circuit simulator. A miniaturized high-temperature superconducting eight-pole filter and a highly miniaturized lumped-element low-temperature superconducting eight-pole filter are designed using this method, and their measured results are reported. View full abstract»

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  • Towards High-Capacity HTS Flywheel Systems

    Page(s): 2272 - 2275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    Adelwitz Technologiezentrum (ATZ) and L-3 Communications Magnet Motor (L-3 MM) are currently mounting a compact-designed flywheel energy storage system (FESS) with total magnetic bearing support. Final assembly and test operation were performed during 2008-2009. After calculations and experiments, we decided to improve rotor stabilization by stiffer geometry. In addition, two dynamical emergency bearings contribute to robust and safe flywheel operation in critical revolution-per-minute situations. A planned energy capacity of 5 kWh is now obtained at about 8000 r/min, whereas an increased capacity of 10 kWh will be stored at a speed of 10 000 r/min. The total weight of the flywheel unit is about 1200 kg plus power electronics and cooling system. The heavier 600-kg rotor causes new design and construction work in mechanical elements, magnetic support bearings, cooling, and power electronics. Due to the here reported construction changes and increased rotor speed, scaling to even larger energy storage performance of 15-20 kWh seems achievable. ATZ and L-3 MM obtained a corresponding order to develop and deliver a 15-kWh/400-kW high-temperature-superconducting FESS for a Korean local grid UPS application. View full abstract»

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  • Mechanical Force Analysis in Heavy-Current HTS Transformers Based on Field and Current Nonuniformity Coupled Analysis

    Page(s): 2276 - 2282
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB) |  | HTML iconHTML  

    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. View full abstract»

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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