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排序方式: 共有111条查询结果,搜索用时 187 毫秒
1.
本文介绍了SIMOVERT MV中压变频器在宣钢炼钢厂一次除尘风机中的应用情况。变频器现场运行表明,采用中压变频器对转炉除尘风机进行调速节能获得了成功,节能效果明显。 相似文献
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Effect of interactions between voltage and current harmonics on the net harmonic current produced by single phase non-linear loads 总被引:2,自引:0,他引:2
The effect of the interaction between both load voltage and current harmonics on the net harmonic current produced by different types of single phase non-linear loads is investigated. Two types of loads are considered: the fluorescent lamps' load and single phase diode bridge rectifiers' load. Studies are done on each load alone and then on the combination of both. The electromagnetic transient program has been used to model these loads. The computer simulations are supported by laboratory testing. The main conclusion of this work is that neglecting the interactions between both voltage and current harmonics will result in incorrect estimation of the harmonic current produced by these loads. Also it is concluded that using a combination of different types of loads can result in a reduction of the current and voltage distortions. 相似文献
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This paper analyzes the stability and switching controllability properties of a single-phase PWM rectifier and its relationship with parameter uncertainty. Based on this analysis, a switching control strategy is proposed that has as objectives (i) to achieve input current tracking and low current THD (total harmonic distortion) as well as (ii) to regulate the output voltage in spite of perturbations. The proposed control does not require a PWM generation step design. Numerical simulations and experimental tests in a 1 kW prototype demonstrate the effectiveness of the proposed controller and illustrate the limits of system's controllability. 相似文献
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本文采用单片微机在软件上对交流励磁机旋转整流器故障信号进行频域分析,从中检测出旋转整流器的各类故障. 相似文献
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The concept of molecular rectifiers introduced by Aviram and Ratner in 1974 has been the starting point of the field of molecular electronics and the possibility of unimolecular rectification has been widely debated ever since. Despite the large amount of publications on this topic over the years, the physical mechanisms leading to this phenomenon have not yet been clarified to the point where a systematic route for enhancing the rectification ratio (RR) of molecules could be suggested. We present here a theoretical study of RR for a range of molecules with a carboxylic group as a bridge between π‐conjugated chains substituted by nitro and amino groups to improve the rectification. We estimate the RR in two distinct ways, namely: i) as the ratio of the threshold electric fields required to transfer one electron between the donor and acceptor units of the molecule and vice versa, using quantum‐chemical calculations based on the semi‐empirical Hartree–Fock Austin Model 1 (AM1) method, ii) as the ratio of the currents in forward versus reverse bias, as obtained with a non‐equilibrium Green's function (NEGF) approach for charge transport through gold/molecule/gold junctions within the framework of density functional theory (DFT). The trends in RR as a function of the molecular structure agree very well when these two methods are compared and can be explained in terms of the relative position of the nitro group within the generated electrostatic potential. These findings allow us to derive some general conclusions about the physical mechanisms behind unimolecular rectification. 相似文献
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基于双Boost交联拓扑的三相功率因数校正器 总被引:1,自引:0,他引:1
研究了基于双Boost交联拓扑的三相功率因数校正器,其主支路三相不控整流器通过外加并联功率因数校正电路来改善网侧电流波形,提高功率因数。首先对主支路的拓扑结构以及工作方式进行分析,总结该拓扑的特点,并针对其特点提出相应的控制策略以及参数设计方案。理论分析和仿真、实验结果表明:这种新型三相功率因数校正器适用于恒功率负载场合,只需通过控制从整流器的选相开关以及双Boost交联变换器即可获得稳定的6脉波直流输出电压、理想的功率因数以及总谐波畸变率,而仅有约1/5的功率经过双Boost交联变换器。 相似文献
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A Study of the Commercial Frequency Component and Doubled Component on the dc Side of Three‐Phase Rectifiers and Their Influence on Electric Railways 下载免费PDF全文
This paper discusses nontheoretical harmonics on the dc‐side of a 12‐pulse rectifier in dc railway systems. These harmonics are the commercial frequency component and the doubled component. The causes of these harmonics are (a) diode forward voltage drop difference, (b) transformer secondary inductance difference, (c) voltage harmonics at the ac‐side of the rectifier, and (d) effects of the voltage induced by adjacent high‐voltage power transmission lines. We evaluated cases (a), (b), and (c), as case (d) has been previously studied 4 . The results of the evaluation were as follows: · The effects of both the transformer secondary inductance difference and the voltage harmonics inside the electric power system are not negligible in some cases in the discussion of the EMC problem among railway equipments. · If there are several traction circuits in parallel, each of which consists of an input filter, an inverter, and several traction motors, the harmonic reduction effect of the filters weakens significantly. 相似文献
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Wenhao Huang Feng Wang Lei Yin Ruiqing Cheng Zhenxing Wang Marshet Getaye Sendeku Junjun Wang Ningning Li Yuyu Yao Jun He 《Advanced materials (Deerfield Beach, Fla.)》2020,32(14):1908040
Ferroelectric field-effect transistors (FeFETs) are one of the most interesting ferroelectric devices; however, they, usually suffer from low interface quality. The recently discovered 2D layered ferroelectric materials, combining with the advantages of van der Waals heterostructures (vdWHs), may be promising to fabricate high-quality FeFETs with atomically thin thickness. Here, dual-gated 2D ferroelectric vdWHs are constructed using MoS2, hexagonal boron nitride (h-BN), and CuInP2S6 (CIPS), which act as a high-performance nonvolatile memory and programmable rectifier. It is first noted that the insertion of h-BN and dual-gated coupling device configuration can significantly stabilize and effectively polarize ferroelectric CIPS. Through this design, the device shows a record-high performance with a large memory window, large on/off ratio (107), ultralow programming state current (10−13 A), and long-time endurance (104 s) as nonvolatile memory. As for programmable rectifier, a wide range of gate-tunable rectification behavior is observed. Moreover, the device exhibits a large rectification ratio (3 × 105) with stable retention under the programming state. This demonstrates the promising potential of ferroelectric vdWHs for new multifunctional ferroelectric devices. 相似文献