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Lan Z.,State Grid Electric Power Research Institute of China | Wen W.,Wuhan University | Ruan J.,Wuhan University | Zhu J.,Wuhan University | Zhu J.,712th Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2015

Temperature is an important index to measure operation state of a power transformer. In this paper, the coupled-field finite-element method is used to calculate the temperature distribution of a ventilated dry-type transformer. Firstly, power loss of each component of the transformer is obtained by three-dimensional (3D) magnetic field calculation. Then the losses are input to the two-dimensional (2D) steady-state fluid-thermal field model as a load to calculate the temperature distribution of the transformer. Temperature measurement experiment shows that the computed temperature rise is in good agreement with the measured value. Moreover, the 2D transient fluid-thermal field is calculated by using the power losses in overcurrent condition. Finally, the maximum allowable temperature value of the transformer is taken as the reference to get the transformer's maximum permissible working time for different overload conditions. The results show that the dry-type transformer can work normally at 10% overload, while the maximum permissible working time is 127, 68, 26, and 8 minutes as the overload is 20%, 30%, 40% and 50%, respectively. This study may provide a reference for understanding overload capability of this kind of ventilated dry-type transformers. ©, 2015, Xi'an High Voltage Apparatus Research Institute. All right reserved. Source


Hu S.-L.,Hubei Normal University | Le Y.-C.,712th Research Institute | Huang L.,Hubei Normal University
Acta Crystallographica Section E: Structure Reports Online | Year: 2010

In the title compound, C 22H 20O 5, the substituted benzene rings are twisted away from the furan ring, making dihedral angles of 54.91 (14) and 20.96 (15)° with the furan ring. The dihedral angle between the two benzene rings is 46.89 (13)°. One ethyl group of one eth-oxy-carbonyl unit is disordered over two sets of sites with occupancies of 0.56 (12) and 0.44 (12). In the crystal, weak intra-molecular C - H⋯O hydrogen bonds link the molecules into chains along the c axis. Source


Wu J.,Wuhan University of Science and Technology | Zhang L.,Wuhan University of Science and Technology | Gong T.,Wuhan University of Science and Technology | Zhu J.,712th Research Institute | And 5 more authors.
Vacuum | Year: 2015

Abstract A high silicon gradient electrical steel sheet with Goss texture has been successfully prepared by a novel and simple process in this work. The FeSi alloy coating with high silicon concentration was firstly deposited on the surface of a common grain oriented electrical steel sheet substrate by cathodic arc plasma deposition technique and the coated sheet was then post-annealed at 850 °C for 6 h in a 70 % N2 - 30 % H2 mixed atmosphere. The results show that after annealing, an excellent Goss texture forms in the FeSi alloy coating with an average silicon concentration of about 6.5 wt. %. The high silicon FeSi alloy coating strongly influences the overall magnetic characteristics of the gradient electrical steel, and the saturation magnetizations of the grain oriented high silicon gradient electrical steel sheet along rolling direction and transverse directions of the substrate are at 251.5 and 233.0 emu/g, respectively. © 2015 Elsevier Ltd. Source


Peng Q.Z.,Central South University | Zhou H.T.,Central South University | Zhong F.H.,Central South University | Ding H.B.,Central South University | And 4 more authors.
Materials and Design | Year: 2015

The effects of homogenization treatment of Mg-8Li-3Al-Y alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and universal testing machine. The experiment results indicated that there existed five phases in the as-cast alloy: α, β, Al2Y, AlLi and MgAlLi2. The spheroidized α phase grew gradually and its microstructure and composition became homogeneous when it was treated at 300°C for 12h. Meanwhile, the alloy has a good comprehensive mechanical property compared with other homogenization schedules. So, a homogenization treatment at 300°C for 12h was determined to be the optimal homogenization treatment for Mg-8Li-3Al-Y alloy. © 2014 Elsevier Ltd. Source


Yu B.,712th Research Institute
Wuli Xuebao/Acta Physica Sinica | Year: 2012

A series of Ag-doped p-type Ag x(Pb 0.5Sn 0.5) 1-xTe compounds is prepared by melting followed by slow-cooling process, and the phase compositions, microstructures and thermoelectric properties are also systematically investigated. The introduction of Ag in Pb/Sn site effectively increases the hole density which is much lower than the theoretically predicated value in the approximation of complete substitution and single acceptor of Ag, in spite of the fact that all samples show finely single phase for the 5% Ag-doped sample. This implies that part of Ag atoms enter into the interstitial sites acting as electron donor to reduce the hole density. With the increase of Ag content, the electrical conductivity increases gradually and the Seebeck coefficient shows an opposite variation tendency, mainly owing to the variation of hole density. Interestingly, the anomalous "crossover" of Seebeck coefficient at about 450 K indicates the transition of dominating valence valley from light-band to heavy-band while temperature is higher than 450 K. Consequently, due to the optimization of hole density and the domination of heavy band with large effective mass, 1% Ag-doped sample obtains a highest power factor of 2.1 mW · m -1 · K -2 at 750 K, which results in a highest ZT of 1.05 combined with the suppressed lattice thermal conductivity via intensifying point defect phonon scattering. This high ZT is ~50% higher than that of Ag-free sample and also higher than commercial p-type PbTe material. Further, the 50% substitution of toxic and heavy Pb by Sn is beneficial for the practical application and environmental sustainability of PbTe-based materials. © 2012 Chinese Physical Society. Source

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