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.
Xiong F.,Huazhong University of Science and Technology |
Wang X.-F.,Huazhong University of Science and Technology |
Hua B.,712th Research Institute |
Yin C.-T.,712th Research Institute
Dianji yu Kongzhi Xuebao/Electric Machines and Control | Year: 2015
Based on the introduction of the stator winding, rotor winding structures and mathematical model under a-b-c axis stationary reference frame of wound-rotor brushless doubly-fed machine (BDFM), the mathematical model of the machine under d-q axis reference frame was proposed. This model was built under arbitrary d-q axis reference frame and convenient for use, time-varying coefficient of the mutual inductance matrices between stator winding and rotor winding was eliminated, computational cost was reduced, facilitates future research on the control strategies, and studying and analyzing the machine performance in both dynamic and steady-state conditions were applied. The machine parameters can be calculated from the design geometry and empirical formula of the machine. Simulation analysis results and experimental data were presented to show the validity of the mathematical model under arbitrary d-q axis reference frame. The establishment of the mathematical model under arbitrary d-q axis reference frame provides the foundation for the study of the performance analysis and control strategy of the machine. ©, 2015, Editorial Department of Electric Machines and Control. All right reserved.
Li J.,Hubei Automotive Industries Institute |
Yu X.,Shanghai FRP Research Institute |
Zhang K.,712th Research Institute
Advanced Materials Research | Year: 2011
The ring-opening reaction between bisphenol A and epichlorohydrin was calculated by Gaussian03. The Density Function Theory (DFT) method were employed to study the geometry structures of bisphenol A and epichlorohydrin and the product was obtained on the base of B3LYP/6-31G+ model in this paper. The transitional states (Ts1, Ts2) during the ring-opening process were found by TS method and the energy changing of the system was proved by IRC calculation. Results showed that the energy reduced by 64.37726kJ/mol during the ring-opening process. The product was confirmed to be thermodynamically stable.
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.
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.
Zhao J.-C.,Huazhong University of Science and Technology |
Du F.-P.,Huazhong University of Science and Technology |
Zhou X.-P.,Huazhong University of Science and Technology |
Cui W.,Huazhong University of Science and Technology |
And 4 more authors.
Composites Part B: Engineering | Year: 2011
Hyperbranched poly(urea-urethane)-grafted multi-walled carbon nanotubes (HPU-MWCNTs) were incorporated in a polyurethane (PU) matrix based on poly(ethylene oxide-tetrahydrofuran) and aliphatic polyisocyanate resin as curing agent. The 9-12 nm thick HPU shell formed on the MWCNTs improved the dispersion of MWCNTs and enhanced the interfacial adhesion between the PU matrix and MWCNTs, leading to improvements in storage modulus and T g of the composites and enhancement of the thermal stability of PU. Thus, composites with 0.5-1 wt% MWCNTs increased the thermal conductivity by about 60-70% when compared to, and retained the high electrical resistivity of, neat PU. © 2011 Elsevier Ltd. All rights reserved.
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.
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.
Liu H.,Harbin Engineering University |
Fan W.,Harbin Engineering University |
Long F.,712th Research Institute |
Shen N.,Harbin Engineering University
IEEE Transportation Electrification Conference and Expo, ITEC Asia-Pacific 2014 - Conference Proceedings | Year: 2014
Ship shaft power generation technology is a kind of effective energy saving way, which can reduce the operating cost in the vessel traffic. Not only bring economic benefits, but also will improve the comprehensive economic indicators of the shipping industry. Compared to the traditional ship shaft power generation system, the shaft power generation systems based on brushless doubly-fed generator (BDFG) has the advantages of smaller capacity of the inverter, lower capital operational costs and higher reliability. The paper analyses the ship operating mode, and presents the control strategy of BDFG. The system hardware environment is established based on the control strategy. The physical verification is developed. The results show that the control strategy has good dynamic performance when the speed and power are change. © 2014 IEEE.