In application of Superconducting magnetic energy storage device (SMES), current lead represents a key development component. This paper will focus on parameters and structure design of hybrid high-temperature superco...
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In application of Superconducting magnetic energy storage device (SMES), current lead represents a key development component. This paper will focus on parameters and structure design of hybrid high-temperature superconductor (HTS) current lead in a SMES with 100 kJ/100 kW class. Based on the theoretical analysis, finite element simulation (FEA) has been used. It studies the thermal influence of variable cross-sectional area, HTS material and the connection between current lead and cryocooler. Some improvements have been proposed to reduce heat losses. At the end of this paper, a whole procedure about hybrid current lead design is given.
A stator earth fault protection scheme based on fault current is presented in this paper. It trips out the faulted generator only if the fault current following the breakdown channel exceeds the tolerance capacity of ...
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ISBN:
(纸本)9781479932559
A stator earth fault protection scheme based on fault current is presented in this paper. It trips out the faulted generator only if the fault current following the breakdown channel exceeds the tolerance capacity of the generator. Otherwise, it will just emit alarm signals. This protection scheme can avoid unnecessary trip-out of large generator, which influences the safe operation of power system, while ensuring the generator security. To achieve the scheme, methods of calculating fault current in real time are provided for three common generator neutral earthing methods basing on the zero-sequence equivalent circuits. An implementation scheme is given on the basis of the sub-harmonic injection protection device. The protection algorithm flow and protection criterion are discussed as well. Simulation results show the accuracy of the fault current calculation method and the validity of the protection scheme.
In this paper, first, the fundamental principle of operation of Brushless Doubly-Fed Machine(BDFM) has been introduced, and then the steady-state equivalent circuit of BDFM was utilised to propose the basic idea of de...
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In this paper, first, the fundamental principle of operation of Brushless Doubly-Fed Machine(BDFM) has been introduced, and then the steady-state equivalent circuit of BDFM was utilised to propose the basic idea of design and give the arithmetic flow chart of BDFM as generator. As calculation of parameters for a variety of different machines is required, the approach of calculating leakage inductance due to slot and harmonic presented here for wound rotor is motivated by versatility. At last, the paper takes a 4/8 poles BDFM as generator for instance and utilizes Vc++6.0 to compile an electromagnetic calculation program to calculate correlative performance data. The paper also analyzes and compares the data with the measurement in experiment.
A double-layer grating structure is proposed, which can show nonreciprocal transmission in near-IR frequency range. The structure is composed of metallic grating with magneto-optical substrate. The nonreciprocity depe...
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Traditionally, based on the pseudo rigid body model method, the ideal stiffness of double parallel four-bar mechanism is obtained by virtual work principle while support arm bar is regard as a rigid rod. However, a te...
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ISBN:
(纸本)9781479910267
Traditionally, based on the pseudo rigid body model method, the ideal stiffness of double parallel four-bar mechanism is obtained by virtual work principle while support arm bar is regard as a rigid rod. However, a terrible error between ideal and real stiffness will be caused in practice as a result of the bending deformation of support arm bar. Therefore, it is urgent to analyze the error of stiffness in double parallel four-bar mechanism and to explore the condition in which the support arm bar could be equivalent to rigid rod. In the paper, an accurate expression of stiffness in the double parallel four-bar mechanism is derived by integral method while the support arm bar is studied as a variable cross section beam through force analysis and deformation analysis. The error between stiffness derived from virtual work principle and integral method is obtained, and whose changing trend with the structural parameters of the right-angle flexure hinge and the support arm bar is analyzed. The result demonstrates that the error is less than 1% when the thickness ratio is larger than 6 and the length ratio is between 6 and 25, that is, the support arm bar can be equivalent to rigid rod, and whose bend deformation can be neglected.
In the application of megawatt(MW) rated railway traction drives, as switching frequency is only several hundred hertz, the bandwidth of current loop is usually limited. Instead of instantaneous current feedback contr...
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The spatial uncertainties of atom force microscopy (AFM) tip position hinder the AFM based nano-manipulation. Although the landmark based tip localization can be applied to improve the tip position accuracy in the tas...
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A class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N‐containing metal–organi...
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A class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N‐containing metal–organic complexes (for example, metal–porphyrin complexes) by a nickel‐catalyzed Yamamoto reaction. Subsequent carbonization of the metal‐incorporated COPs led to the formation of COP‐derived graphene analogues, which acted as efficient electrocatalysts for oxygen reduction in both alkaline and acid media with a good stability and free from any methanol‐crossover/CO‐poisoning effects.
In this work, the conductive network, probability, and percolation threshold of nanorod/polymer composites under tensile strain are investigated using the molecular dynamics simulation. The internal interactions, incl...
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