2008 Vol. 6, No. 2

Display Method:
Special Issue on High Temperature Superconductivity
Fabrication of HTS dc Bias Coil for 35kV/90MVA SFCL
Jing-Yin Zhang, Wei-Zhi Gong, Zheng-Jian Cao, Hui Hong, Bo Tian, Yang Wang, Jian-Zhong Wang, Xiao-Ye Niu, Ying Xin
2008, 6(2): 97-100.
Abstract:
For a saturated iron core fault current limiter, superconductor is the only suitable material to make the dc bias coil, especially when the device is used in a high voltage power grid. Commonly, superconducting wires are used to wind the dc bias coil. Since the performance of the wires changes greatly under magnetic fields, the calculation of the field spatial distraction is essential to the optimization of the superconducting magnet. A superconducting coil with 141000 ampere-turns magnetizing capacity made of 17600 meters of BSCCO 2223 HTS tapes was fabricated. This coil was built for a 35kV/90MVA saturated iron-core fault current limiter. Computer simulations on magnetic field distribution were carried out to optimize the structural design, and experiments were done to verify the performance of the coil. The configuration and the key parameters of the coil will be reported in this paper.
Influences of Resistor-Type Superconducting Fault Current Limiter on Power System Transient Stability with Asymmetrical Short-Circuit Faults
Xue-Ping Gu, Zhi-Long Yang
2008, 6(2): 101-107.
Abstract:
The transient stability of a single machine to infinite-busbar power system with resistortype superconducting fault current limiters (SFCL) is analyzed under asymmetrical short-circuit fault conditions. The SFCL is considered to introduce a resistance into the three-phase circuits when faults occur. Based on the power-angle curves for different short-circuit conditions of the single-line to ground, double-line to ground and line to line short-circuit faults, the influences of the SFCLs on transient stability are analyzed in detail. The time-domain simulation of transient stability is carried out to verify the analytical results.
Live-Grid Operation and Maintenance of the 35 kV/121MVA Superconducting Cable System
Huan-Huan Li, An-Lin Ren, Ying Xin, Hui Hong, Zhi-Li Chen, Lin-Na Shi
2008, 6(2): 108-111.
Abstract:
A 33.5 m, 35 kV/121 MVA, three-phase, warm dielectric HTS power cable system was successfully installed and activated in China Southern Power Grid at the Puji substation in Kunming on April 19th of 2004, supplying electricity to four industrial customers (including two metallurgical refineries) and a residential population of about 100000. In this paper, we give an update on the operation and maintenance status of the system and comments on reliability issues. We conclude that the superconducting cable system is currently quite robust and feasible for particular utility applications, and it will be improved by advancement in cryogenic equipment and system technology.
Structural Parameter Optimization of Multilayer Conductors in HTS Cable
Yan Mao, Jie Qiu, Xin-Ying Liu, Zhi-Xuan Wang, Shu-Hong Wang, Jian-Guo Zhu, You-Guang Guo, Zhi-Wei Lin, Jian-Xun Jin
2008, 6(2): 112-118.
Abstract:
In this paper, the design optimization of the structural parameters of multilayer conductors in high temperature superconducting (HTS) cable is reviewed. Various optimization methods, such as the particle swarm optimization (PSO), the genetic algorithm (GA), and a robust optimization method based on design for six sigma (DFSS), have been applied to realize uniform current distribution among the multilayer HTS conductors. The continuous and discrete variables, such as the winding angle, radius, and winding direction of each layer, are chosen as the design parameters. Under the constraints of the mechanical properties and critical current, PSO is proven to be a more powerful tool than GA for structural parameter optimization, and DFSS can not only achieve a uniform current distribution, but also improve significantly the reliability and robustness of the HTS cable quality.
Analysis of DC Power Transmission Using High Tc Superconducting Cables
Jun-Lian Zhang, Jian-Xun Jin
2008, 6(2): 119-124.
Abstract:
A conceptual superconducting DC cable model is designed and its magnetic fields distribution is analyzed with Ansoft/Maxwell soft. A DC Power transmission system is also studied by using the Matlab/Simulink. With the DC Line and AC Ground Fault, the system losses analysis is introduced.The analysis results mainly include the magnetic fields distribution of the HTS cable model with Ansoft/Maxwell, the system loss, the DC Line and AC Ground Fault with Matlab/Simulation.
A Permanent Magnet Linear Synchronous Motor Drive for HTS Maglev Transportation Systems
You-Guang Guo, Jian-Xun Jin, Lu-Hai Zheng, Jian-Guo Zhu, Hai-Yan Lu
2008, 6(2): 125-129.
Abstract:
A permanent magnet linear synchronous motor (PMLSM) for a high temperature superconducting (HTS) maglev system has been studied, including the motor structure, control strategy, and analysis techniques. Finite element analysis (FEA) of magnetic field is conducted to accurately calculate major motor parameters. Equivalent electrical circuit is used to predict the drive's steady-state characteristics, and a phase variable model is applied to predict the dynamic performance. Preliminary experiment with a prototype has been made to verify the theoretical analysis and the HTS-PM synchronous driving technology.
Development of HTS Transformers and a 10 kVA HTS Transformer Prototype Design
Xiao-Yuan Chen, Jian-Xun Jin
2008, 6(2): 130-136.
Abstract:
With the improvement of high temperature superconductor (HTS) practical performance, research and development concerning the applications of HTS transformers have been progressed actively worldwide. This paper provides a comprehensive summary on various HTS transformers, and studies the design of a single-phase 10 kVA (220V/24V) HTS transformer prototype to verify HTS for practical transformer applications.
High Temperature Superconducting Magnetic Energy Storage and Its Power Control Technology
Xiao-Yuan Chen, Jian-Xun Jin, Kai-Meng Ma, Ju Wen, Ying Xin, Wei-Zhi Gong, An-Lin Ren, Jing-Yin Zhang
2008, 6(2): 137-142.
Abstract:
High temperature superconducting (HTS) power inductor and its control technology have been studied and analyzed in the paper. Based on the results of simulations and practical experiments, a controlled release scheme has been proposed and verified for developing a practical HTS SMES prototype.
Fabrication of YBCO Coated Conductors on Biaxial Textured Metal Substrate by All-Sputtering
Xiao Han, Jing-Tan He, Jie Xiong, Bo-Wan Tao
2008, 6(2): 143-146.
Abstract:
CeO2/YSZ/CeO2 buffer layers were prepared on biaxial textured Ni-5at.%W substrate by direct-current magnetron reactive sputtering with the optimum process. YBCO thin films were deposited on CeO2/YSZ/CeO2 buffered Ni-5at.%W substrate at temperature ranging from 500℃ to 700℃ by diode dc sputtering. By optimizing substrate temperature, pure c-axis oriented YBCO films were obtained. The microstructures of CeO2/YSZ/CeO2 buffer layers were characterized by X-ray diffraction. A smooth, dense and crack-free surface morphology was observed with scanning electron microscopy. The critical current density Jc about 0.75 MA/cm2 at 77 K was obtained.
Phase Transformation and Optimized Growth of TFA-MOD REBa2Cu3O7-x Films for Coated Conductors
Zhi-Yong Liu, Bo Gao, Li-Liang Ying, Feng Fan, Yu-Ming Lu, Chuan-Bing Cai, T. Thersleff, B. Elke
2008, 6(2): 147-151.
Abstract:
Several types of REBa2Cu3O7-x (REBCO, RE=Y, Ho etc.) films are prepared on single crystal substrate LaAlO3 by TFA-MOD method. The phase transformation and optimized growth conditions in the crystallization are studied. Compared with SmBCO and GdBCO, high quality YBCO and HoBCO films are relatively easy to produce. It is revealed that the YBCO grains can form at low temperatures such as 730℃ during the initial heating ramp. With a high heating rate of 20 K/min and a low oxygen pressure of 100 ppm, the optimum growth temperature is around 780℃, at which the films show a Jc value of 2.88 MA/cm2. Further decrease of the heating rate may produce the highquality YBCO film with a higher Jc of 3.65 MA/cm2. The temperature dependence of resistances in various magnetic fields up to 9 T shows that the present TFAMOD YBCO and HoBCO films have similar superonducting transition temperature and magnetotransport properties.
Hg Substitution Effect on Superconductivity and Crystal Structure of MgB2
Ya-Jing Cui, Yong-Liang Chen, Ye Yang, Yong Zhang, Cui-Hua Cheng, Yong Zhao
2008, 6(2): 152-156.
Abstract:
Polycrystalline Mg1-xHgxB2 samples with x=0, 1%, 2.5%, 5%, 7.5%, and 10% have been synthesized by solid-state reaction. Different from the substitution effect of Al, C, Li, etc. on crystal structure of MgB2, Hg substitution for Mg results in an increase of the lattice constant in both a and c directions. The superconductivity of MgB2 is also suppressed by Hg substitution. The observed suppression of super-conductivity by Hg substitution is discussed in terms of the interband impurity scattering effect in two-band superconductors.
Improvement in Superconducting Properties of MgB2 Superconductors by Nanoscale Carbon-Based Compound Doping
Si-Hai Zhou
2008, 6(2): 157-161.
Abstract:
MgB2 is a relatively new superconductor; it has attracted great interest from superconductor researchers all over the world. Thorough investigations have been carried out to study the material fabrication, as well as to study the material and superconducting properties from a fundamental physics point of view. The University of Wollongong has played a very active role in this research and a leading role in the research on high critical current density and high critical magnetic fields. Our recent research on the improvement of critical current density and the upper critical magnetic field by carbon-based compound doping is reviewed in this paper.
Magnetic Properties of Al-Doped Na0.7Co1-xAlxO2
Yong Zhang, Zhi-Huan Wu, Cui-Hua Cheng, Yong Zhao
2008, 6(2): 162-165.
Abstract:
Single phase polycrystalline samples Na0.7Co1-xAlxO2 (x=0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30) were prepared by solid state reaction. The magnetic properties from 5 K to 300 K have been studied by dc and ac magnetic susceptibility measurements. Samples with lower doping quantity (x=0, 0.05, 0.10) showed paramagnetic behaviors, but those with higher doping quantity (x=0.20, 0.25, 0.30) showed spin-glass behaviors with a freezing temperature (Tf) of about 13 K.
Effects of Doping Mn on Nd1.85Ce0.15CuO4 System
Fa-She Wang, Yong-Liang Chen, Ye Yang, Yong Zhang, Cui-Hua Cheng, Yong Zhao
2008, 6(2): 166-170.
Abstract:
Nd1.85Ce0.15Cu1-xMnxO4 samples with doping level up to 20% have been synthesized by solid-state reaction method. The influence of Mn on their normal-state transport, crystal structure, superconductivity and magnetic properties has been investigated. For the samples with x0.03, magnetization under zero-field cooling indicates that the magnetic state changes from ferromagnetic to paramagnetic at T100 K, which can be explained with the interaction between Mn4+ and Mn3+. The electrical resistivity of samples increases with Mn doping. For the samples with doping level lower than 0.20, initially increases with the decrease of temperature, i.e., d/dt0, and then shows superconductivity transition at T20 K. The results suggest the coexistence of superconductivity and ferromagnetic ordering in Mn doped Nd1.85Ce0.15CuO4.
Superconductivity in Hg-Substituted BaPb0.75Bi0.25O3
Yong-Liang Chen, Ya-Jing Cui, Yong Zhang, Cui-Hua Cheng, Yong Zhao
2008, 6(2): 171-174.
Abstract:
A series of Hg-doped BaPb0.75Bi0.25O3 with a nominal composition of BaPb0.75-xHgxBi0.25O3 (x=0 to 0.40 with 0.05 intervals) have been synthesized by solid-state reaction. These compounds exhibit a cubic perovskite-related structure with the lattice parameter being expanded by Hg doping. Superconducting transition temperature Tc and superconducting volume fraction are suppressed by Hg doping in the low doping level region (0x0.25). However, further increasing Hg content makes the superconductivity recovered at x0.3. The superconductivity suppression in Hg-doped BaPb0.75Bi0.25O3 can be explained by the decrease of electron carrier concentration as well as the bandnarrowing-induced electron localization.
Temperature Dependence of Growth Mechanism for Nanoscale High Tc Superconductors
Wu-Ming Chen, Mustafa Yavuz, Jian-Xun Jin
2008, 6(2): 175-180.
Abstract:
The growth mechanisms of high temperature Yttrium-and Bismuth-based-superconductors were investigated at nanoscale. We started with studying the growth relationships among the three phases of Bi-2201, Bi-2212, and Bi-2233, and then extended to another growth mechanism of Bi-2223 and the growth of yttrium-based high-temperature nanosuperconductors (nano-YBCO). A time dependence of growth experiment was performed. In this experiment, the Bi-based superconductors grew within different sintering periods, and its three phases were determined by X-ray diffraction. And then, a time dependence of growth model was suggested to explain the experimental facts. With this model, governing equations were derived to quantitatively describe the growth and decomposition mechanisms during sintering period. The results calculated from the derived equations were well in agreement with the experimental data. We also suggested an alternative growth mechanism for the Bi-2223 phase, which was supported by an observation of transmission electron microscopy (TEM). The nano-YBCO also grew, and their orthorhombic crystal structures were determined by the TEM. The superconducting properties of Bi-2223 were investigated by the measurements of ac magnetic susceptibility. It is expected that the derived equations will fit the alternative experimental growth mechanism of the Bi-2223 phase and the nano-YBCO growth mechanism, too.
Analysis of Vertical Oscillations of a Permanent Magnet Freely Levitated above an YBCO Bulk in an AC External Magnetic Field
Yong Zhang, Ya-Li Zhang, Cui-Hua Cheng, Yong Zhao
2008, 6(2): 181-184.
Abstract:
The effect of the moving speed of permanent magnet (PM) on levitation force between PM and high temperature superconducting (HTS) bulk is analyzed and described in the PM-HTS levitation system. The PM vibration characteristic in the PM-HTS system is investigated. The PM may collide with the HTS in vibration if the amplitude and frequency of driving force satisfy the relationship Pmin=Afn. When the load of the system is below a threshold, the minimal collision amplitude of the driving force increases with the load increasing, however, it sharply drops to zero when the load exceeds the threshold. With the increase of the initial height of the PM, the threshold load increases, but the minimal driving force which causes a collision between PM and HTS decreases.
Physical Effects of Mechanical Processes on Bi-2223 Tapes
Wu-Ming Chen, Jian-Xun Jin, Mustafa Yavuz
2008, 6(2): 185-190.
Abstract:
The effects of intermediate mechanical deformation (IMD) and bending processing on Bi-2223 tapes were studied. Bi-2223 tapes were manufactured by powder-in-tube process with an IMD. Normal rolling (NR), pressing (P) and sandwich rolling (SR) with different reduction rate were used in the IMD. And there were an optimum reduction rate existing for the three MID techniques, at which critical current reached maximum. Critical current densities Jc of Bi-2223 crystals were measured with an applied magnetic field B respectively parallel to ab face and c axis. Relations of Jc dependences of reduction rate and superconducting materials density D were respectively studied and showed a Gaussian distribution law. Maximum pinning force density Fmax and irreversible magnetic field Birr were introduced to describe the effects of mechanical processing. Analysis of experimental results showed that Jc, Fmax and Birr were linear dependence on D. Obviously, increasing D was a vital way to enhance Jc. Bending experiments were performed for SR tapes sheathed by Ag and Ag/Sb and Ag/Mg alloy, respectively. Silver alloy sheathed tapes showed better bending properties than pure silver sheathed one. Therefore, silver alloy sheathed, optimum reduction rate of IMD, and increasing D for Bi-2223 tapes' applications were important technical strategies to enhance their mechanical, electrical, and magnetic properties.
SVPWM Techniques and Applications in HTS PMSM Machines Control
Zheng-Guang Wang, Jian-Xun Jin, You-Guang Guo, Jian-Guo Zhu
2008, 6(2): 191-197.
Abstract:
This paper introduces the principle of space vector pulse width modulation (SVPWM), and discusses a method for implementing the SVPWM based on MATLAB/SIMULINK, as well as modeling of AC servo system with permanent magnet synchronous motor (PMSM). Simulation results show that the model is effective, and the method provides a frame of reference for software and hardware designs which can be applied in high temperature superconducting (HTS) flywheel energy storage system (FESS) and linear motor (LM).
LabVIEW and PCI DAQ Card Based HTS Test and Control Platforms
Hui-Bin Zhao, Jian-Xun Jin, Pu-Chun Jiang, Wen-Hui Gao, Zi-Lu Liang
2008, 6(2): 198-204.
Abstract:
This paper introduces the relevant parameters and related characteristics of the LabVIEW and PCI6221 data acquisition (DAQ) card, describes in detail the approach of building the measure and control platform of virtual instrument (VI) using LabVIEW and PCI6221, specifically discusses the system's application in high temperature superconductor (HTS) research including the test of HTS volt-ampere characteristics and the HTS magnetic energy storage. The experiments prove that the VI test and control system is easy to build and convenient to use.
Investigation of Properties of Motion of Superconductive Electrons in Superconductors by Nonlinear Quantum Mechanical Theory
Xiao-Feng Pang
2008, 6(2): 205-211.
Abstract:
The properties and rules of motion of superconductive electrons in steady and time-dependent non-equilibrium states of superconductors are studied by using the Ginzberg-Landau (GL) equations and nonlinear quantum theory. In the absence of external fields, the superconductive electrons move in the solitons with certain energy and velocity in a uniform system, The superconductive electron is still a soliton under action of an electromagnetic field, but its amplitude, phase and shape are changed. Thus we conclude that super-conductivity is a result of motion of soliton of superconductive electrons. Since soliton has the feature of motion for retaining its energy and form, thus a permanent current occurs in superconductor. From these solutions of GL equations under action of an electromagnetic field, we gain the structure of vortex lines-magnetic flux lines observed experimentally in type-II superconductors. In the time-dependent nonequilibrium states of superconductor, the motions of superconductive electrons exhibit still the soliton features, but the shape and amplitude have changed. In an invariant electric-field, it moves in a constant acceleration. In the medium with dissipation, the superconductive electron behaves still like a soliton, although its form, amplitude, and velocity are altered. Thus we have to convince that the superconductive electron is essentially a soliton in both non-equilibrium and equilibrium superconductors.
Design of TE01Δ Test Probe for Measuring the Microwave Surface Resistance of HTS Thin Film
Cheng Zeng, Zheng-Xiang Luo, Qi-Shao Zhang, Kai Yang
2008, 6(2): 212-215.
Abstract:
A new TE01 test probe with proper transmission factor is fabricated for the measurement of surface resistance of high temperature superconductor (HTS) thin film. Coupling holes instead of coupling loops are used in the probe for its easier machining and relatively low loss. Two 6 mm3 mm8 mm dielectric waveguides, one side of them is coated by silver, are used for coupling. The measurement result of S21 agrees well with the simulation because the size of the probe can be rigidly controlled by machine. The microwave surface resistance of four YBCO/MgO films are measured at 77 K and 12 GHz and scaled to 10 GHz according to the f2 rule. The average surface resistance of four HTS thin films is 0.38 m, the standard deviation and relative standard deviation of one single HTS thin film are 0.009 m and 2.4%, respectively.
Superconducting Electronics Research at CSIRO Australia-20 Years after Discovery of HTS
Jia Du, Cathy P. Foley, Keith L. Leslie
2008, 6(2): 216-224.
Abstract:
CSIRO has had a long-term research effort in superconductivity, in particular, since the discovery of HTS which promised big prospects. Significant progress has been made in research and development of HTS electronic devices and systems for practical applications such as mineral and exploration as well as some niche applications in emerging science and technology areas. This article presents an overview of the CSIRO research activities in HTS superconducting electronics since 1987, outlining the HTS junction and device technology as well as various application systems develop by the group.
High Temperature Superconductivity in the Past Twenty Years Part 1-Discovery, Material, and Theory
Jian-Xun Jin
2008, 6(2): 225-236.
Abstract:
Twenty years after the discovery of hightemperature superconductors (HTSs), the HTS materials now have been well developed. Meanwhile the mechanism of superconductivity is still one of the topical interests in physics. The achievements made on HTS materials and theories during the last twenty years are reviewed comprehensively in this paper.
High Temperature Superconductivity in the Past Twenty Years Part 2-Towards to Practical Applications
Jian-Xun Jin
2008, 6(2): 237-254.
Abstract:
After discovering high temperature superconducting materials 20 years ago, the preparation of applicable HTS materials has been pursued along with HTS mechanism and characteristic study. At present, the focus on the applied HTS technology has been moving to the industrial preparations from the laboratory research stage, and the technology has been well verified for practical applications from small to large scales. The fabrication techniques of engineering HTS materials are being industrialized; and various HTS devices are also on the way towards practical applications. This paper provides a comprehensive summary on the applied high temperature superconductivity with regard to various applicable HTS materials, their preparation techniques and characterization, and applications in a wide range.