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Qu T.,Tsinghua University | Song P.,Tsinghua University | Yu X.,Tsinghua University | Gu C.,Tsinghua University | And 7 more authors.
Superconductor Science and Technology | Year: 2014

High temperature superconducting (HTS) armature windings have the potential for increasing the electric loading of a synchronous generator due to their high current transport capacity, which could increase the power density of an HTS rotating machine. In this work, a novel synchronous generator prototype with an HTS stator and permanent magnet rotor has been developed. It has a basic structure of four poles and six slots. The armature winding was constructed from six double-pancake race-track coils with 44 turns each. It was designed to deliver 2.5 kW at 300 rpm. A concentrated winding configuration was proposed, to prevent interference at the ends of adjacent HTS coils. The HTS stator was pressure mounted into a hollow Dewar cooled with liquid nitrogen. The whole stator could be cooled down to around 82 K by conduction cooling. In the preliminary testing, the machine worked properly and could deliver 1.8 kW power when the armature current was 14.4 A. Ic for the HTS coils was found to be suppressed due to the influence of the temperature and the leakage field. © 2014 IOP Publishing Ltd.


Song P.,Tsinghua University | Qu T.,Tsinghua University | Yu X.,Tsinghua University | Li L.,Tsinghua University | And 6 more authors.
Physica C: Superconductivity and its Applications | Year: 2013

A prototype HTS synchronous generator with a permanent magnet rotor and HTS armature windings was developed. The rated armature frequency is 10 Hz. The cryogenic Dewar is tightly surrounded outside the iron core. Both HTS coils and the iron core were cooled by using conduction cooling method. During the process of no-load running, the no-load loss power data were obtained through the torque measurement. The temperature evolution characteristics of the stator was measured by PT-100 temperature sensors. These results show that the no-load loss power at around 77 K are much larger than that at room temperature. The possible reason for the no-load loss increment is discussed. The ac loss power of one individual HTS coil used in this generator was also tested. Compared with the iron loss power, the ac loss power is rather small and could be neglected. © 2013 Elsevier B.V. All rights reserved.


Deng S.,Tsinghua University | Qu T.,Tsinghua University | Bao R.,Innova Superconductor Technology Co. | Lin G.,Tsinghua University | And 3 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2015

Pure Bi2Sr2Ca2Cu3Ox (Bi-2223) phase is hard to be achieved in Bi-2223 thin films fabricated by using chemical solution deposition (CSD) due to the volatilization of specific elements. Two protected sintering methods were proposed in this work to enhance the phase purity of CSD Bi-2223 thin films. One method is two deposited thin films stacked "face-to-face" (FTF) and then sintered. A "substrate/precursor film/precursor film/substrate" architecture was used during sintering instead of common "precursor film/substrate" architecture. The other method was named "sealed face-to-face" (SFTF). The FTF structure was buried in Bi-2223 powders and then sealed in a silver envelope before sintering. Different sintering temperature and sintering time were investigated in an 8% O2 (N 2 balance) atmosphere. The volume fraction of Bi-2223 phase could be enhanced to 17% by using the FTF method, and 68% by using the SFTF method. © 2002-2011 IEEE.


Chen X.P.,Chongqing University | Yu X.W.,Chongqing University | Li M.Y.,Northeastern University China | Sun H.B.,Innova Superconductor Technology Co. | Liu Q.,Chongqing University
Journal of Superconductivity and Novel Magnetism | Year: 2013

The influence of green tape thickness on the Bi-2223 phase formation and texture evolution in Ag/Ni composite-sheathed tapes fabricated by the "powder-in-tube" technique has been studied. Microstructural observations by SEM as well as critical current density (Jc) measurements at 77 K, 0 T have been performed to analyze the performance of the tapes. The results show an important influence of the green tape thickness on the critical current depending on the content and texture of Bi-2223 phase. The Jc increases with decreasing thickness. Moreover, texture measured by omega scans shows that the texture of the Bi-2223 phase is significantly influenced by the thickness of the green tape after the first and final sintering processes. Alignment of Bi-2223 grains in the thin tapes is much better. Higher performance of Ag/Ni composite-sheathed Bi-2223 tapes can be obtained by controlling the thickness of the green tapes. © 2012 Springer Science+Business Media, LLC.


Chen X.,Chongqing University | Yu X.,Chongqing University | Zhang J.,Chongqing University | Li M.,Northeastern University China | And 2 more authors.
Solid State Sciences | Year: 2011

The growth kinetics of the (Bi,Pb)2Sr2Ca 2Cu3O10 (Bi-2223) grains in Ag/Ni sheathed tapes have been investigated by the means of XRD and SEM. Samples were sintered at 837 °C for various time under low oxygen partial pressure. Monofilament tape after sintered for 50 h has a critical current (Ic) of 3.6 A. An analysis of the Bi-2223 phase evolution using Avrami relation reveals a three-stage process with obvious changes of the n-exponent during the Bi-2223 formation after about 3 and 20 h sintering. Secondary electron images show that the Bi-2223 grains nucleate at the initial stage and grow within a-b plane until their edges impinge each other. The thicknesses of Bi-2223 grains are measured statistically after various sintering time. The data denote that the thickness increase with the extension of sintering time and become more rapidly after 10 h sintering. A detailed process describing the growth of Bi-2223 grains is presented basing on the n-exponent and microstructural observation. © 2011 Elsevier Masson SAS. All rights reserved.


Ye C.L.,Northeastern University China | Li M.Y.,Northeastern University China | Chen X.P.,Chongqing University | Sun H.B.,Innova Superconductor Technology Co. | And 2 more authors.
Physica C: Superconductivity and its Applications | Year: 2011

To reduce the cost of Bi-2223 superconducting tapes, we prepared Bi-2223 tapes by the powder-in-tube process using a bimetallic sheath consisting of Ag and Ni. Ag was in contact with the superconducting ceramic core and acted as a protective layer against reaction between the external Ni sheath and the internal superconducting core. We remove Ni on one edge of the tape in order to provide a path for oxygen diffusion. After two step heat treatments, the critical current density of sample is 9307 A cm-2. SEM photographs and XRD results show that there are some Bi-2212 phase in samples conducted two step heat treatments. It is suggested that the heat treatment process should be optimized in the future research in order to decrease the thickness of NiO layer, to reduce the fraction of Bi-2212 phase, and to improve superconducting performance of Bi-2223/Ag/Ni tape. © 2011 Elsevier B.V. All rights reserved.


Chen X.P.,Chongqing University | Yu X.W.,Chongqing University | Liu M.,Chongqing University | Li M.Y.,Northeastern University China | And 2 more authors.
Journal of Superconductivity and Novel Magnetism | Year: 2012

10-meter-long Ag-Ni bimetallic sheathed (Bi,Pb)- 2223 tapes with outer nickel sheath and inner silver sheath have been successfully fabricated by the "Powder in tube" technique. Microstructure and phase evolution studies by means of SEM and XRD, as well as critical current density (Jc) measurements have been performed. It is found that the nickel sheath and dwell time in the first sintering process have great influences on the texture evolution, phase transformation and Jc of the Bi-2223/Ag/Ni tapes. Monofilament (Bi,Pb)-2223 tape with a Jc of 6656 Acm-2 and 61-filament tape with a Jc of 12420 Acm-2 are obtained. Although using composite bimetallic sheaths can reduce production costs and improve mechanical properties of the Bi-2223 tapes, the Bi-2223 content and Jc of Bi-2223/Ag/Ni tapes are relatively lower than that of traditional Bi-2223/Ag tapes. Meanwhile, due to higher Bi-2223 content and better alignment of Bi-2223 grains, tapes with 61-filament have higher J c than mono-filament tapes. ©Springer Science+Business Media, LLC 2012.


Ji C.-H.,University of Science and Technology Beijing | Li J.-Q.,University of Science and Technology Beijing | Huang W.-J.,University of Science and Technology Beijing | Bao R.,Innova Superconductor Technology Co. | And 2 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2010

A method for the determination of trace gold by inductively coupled plasma atomic emission spectrometry (ICP-AES) in mine sample was proposed. The instrument parameters were optimized and the media of solution and interferences were studied systemically. The results showed that in less than 10%(φ) aqua regia medium, the acids had no influences on the determination, and after removing common cations in mineral samples by using 10% hydrochloric acid(φ), the residual matrix elements had no effect on the determination of Au with ICP-AES. The silicon in samples had serious spectral interference to Au 208.2 nm, and the spectral interference was corrected with interference coefficient using the 251.6 nm silicon line. With 10% HCl to remove the matrix and interference correction coefficient to eliminate the interference of silicon, trace gold in high-sulfur tailings samples was determined, the result was identical with the reference values by the method of enrichment with activated carbon-atomic absorption spectrometry. Under the experimental conditions, the detection limit for gold in mine sample was 0.10 g·t-1.


Fan L.-X.,University of Science and Technology Beijing | Li J.-Q.,University of Science and Technology Beijing | Fan H.-L.,University of Science and Technology Beijing | Sun J.-L.,University of Science and Technology Beijing | And 4 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2011

A new method for the determination of trace nickel in superconductor powder by ICP-AES was proposed. The instrument parameters were optimized, and the matrix effects as well as the method of eliminating interferences were also studied systemically. The results showed that matrix interference in the superconductor powder was serious when the amount of matrix increased, and the repeatability as well as the accuracy was poor, so it was necessary to used separation and preconcentration to improve the accuracy and precision. In this experiment, Ni-diacetyl dioxime complexes were enriched by toluene extraction in alkaline condition after eliminating the interference of major element Bi and partial Pb, Sr, Ca and Cu by eluting with anion exchange resin, then the Ni-complexes were back extracted by diluted hydrochloric acid. The enrichment conditions were investigated in detail and the recovery rate of Ni was higher than 95%. Under the optimal condition, an artificial sample was analysed, the result showed that the found values were identical with reference values, and the RSD and detection limit were 1.9% and 0.19 μg·g-1, respectively. The method has been applied to the determination of trace nickel in Bi-based superconductor powder samples with satisfactory results.


Chen Q.,Jiangsu University | Liu G.,Jiangsu University | Liu Z.,Jiangsu University | Li X.,Innova Superconductor Technology Co.
IEEE Transactions on Applied Superconductivity | Year: 2014

The fully high temperature superconductor (HTS) motor can offer high efficiency, small size, and high torque density. However, the available fully HTS motors suffer from the high cost cooling system. There should be two cooling systems for the HTS armature coils and the HTS field coils, particularly, the rotating HTS field coils. In this paper, a new fully stator-HTS motor is proposed. The key of the proposed motor is that both the HTS armature coils and HTS field coils are placed in the stator. Hence, only one cooling system is needed. Meanwhile, all these stationary HTS coils avoid the rotated cooling system. Then, the cost of the cooling system can be reduced greatly. Moreover, since the rotor structure is similar with the switch reluctance motor, the proposed motor provides the advantages of simple rotor configuration and high mechanical robustness. The electromagnetic performances of the newly designed stator-HTS motor are analyzed including the flux, back electromotive force as well as torque. The effectiveness of the theoretical analysis is verified by the finite-element analysis. © 2014 IEEE.

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