浅析调速变频器谐波的产生及抑制方法

调速变频器在工业生产中的应用十分普遍,但由于变频器也容易产生的谐波电流,对供电系统、负载及其他邻近电气设备产生干扰,因此,调速变频器谐波干扰问题引起人们的重视。本文主要介绍了变频器谐波的危害及产生的原因,并提出了抑制谐波干扰的技术方法,对提高变频器运行的可靠性和安全性提供参考。     

动态无功补偿滤波装置在污水厂的应用

对变频器的谐波产生机理、谐波干扰途径以及危害进行了分析,同时介绍了用动态无功补偿滤波装置来滤除谐波的方法,并在污水处理厂的应用中取得了满意效果。     

高压变频器的高次谐波分析与控制

现代电力电子技术的应用极大地推动了电力系统的发展,与此同时也给电力系统带来了非常严重的谐波污染问题。高压变频器的高次谐波干扰对电力系统造成了严重影响,必须采取有效的措施来加以抑制。本文分析了高压变频器高次谐波污染的原因及其造成的危害,并提出了抑制谐波的措施。     

双PWM变频器在电梯中的应用

针对传统变频器能量不可逆、谐波污染等缺点,介绍了在电梯中应用的一种新型变频器——双PWM变频器,通过它实现能量的双向流动,节约能源。     

双PWM变频器在电梯中的应用

本文针对传统变频器能量不可逆、谐波污染等缺点,主要介绍了在电梯中应用的一种新型变频器——双PWM变频器,实现了能量的双向流动,节约了能源。     

针对高次谐波引起的电磁干扰的解决方案

本文叙述了电磁兼容性和电力系统谐波的产生,变频器谐波及其电磁干扰问题,并通过一个电磁兼容实例来进行论述,最后提出对由高次谐波引起的电磁兼容问题的解决办法。由于电力系统中非线性负载的数量越来越多,而作为其中主要一大类的变频器的应用日益广泛,电子电气设备对电磁兼容性的要求越来越高,特别是高次谐波所带来的电磁兼容问题。     

浅谈变频器运行过程中存在的问题及其对策

针对大功率设备应用变频器运行过程中存在的谐波问题、负载匹配问题和发热问题,逐一进行了分析,并提出了相对应的解决方案,以推广变频器的应用,充分发挥变频器节约能源和投资少的优点。     

变频器对油田电动机性能影响的研究

随着油田产量逐年递减,设备负载率不断降低,变频调速作为电动机节能的主要方法得到广泛应用。以大庆油田为例,超过30%的电动机使用变频器来调节转速。变频器在使用过程中,输入、输出端都会产生大量的谐波,这些谐波会造成电动机效率的降低、运行温度的升高、振动和噪声的增加等影响。通过对相关影响因素进行研究,尤其是变频器对电动机损耗、温升、噪声振动及绝缘的影响提出了对应的整改措施。经过分析,变频器对电动机影响最大的是产生的谐波,有效的消减谐波就可以减小对电动机效率和寿命影响,合理匹配变频器可以减小对电动机温升及噪声振动的影响。     

电梯和电源高次谐波

介绍交流变频器的谐波特性和抑制电梯变频器谐波的措施，讨论电梯变频器的谐波与电网的关系。     

基于有源滤波器在烟草行业低压配电系统中应用的分析

本文介绍了有源滤波器在低压配电网络中的应用,通过实时监测供电线路中变频器、变速传动装置、各种直流电源等设备产生的高次谐波,动态抑制高次谐波,消除谐波电流对供电网络中设备的危害,降低能源的浪费,提高供电质量,保证供电设备及用电设备的安全运行。     

Renewable energy harvesting from water flow

The hydrokinetic energy of flowing water is plentiful, environment-friendly, renewable and can be harvested. This paper reports a new energy harvesting system using vortex-induced vibration (VIV). The proposed convertor harvests vibrations of a bluff body resulting from interaction of the alternating vortices created by the unsteady separation. These vortices are shed from the sides of the bluff body and form a pattern in the wake known as the von Kármán vortex street. The vortices create unsteady loading and induce vibrations with a predictable frequency and amplitude. Assisted by the bluff body with specific geometry and piezoelectric generators, the kinetic energy of the water flow can be converted into mechanical vibrations and electrical energy. In order to maximise the output energy of the harvester, the natural frequency of the mechanical system needs to lock into the frequency of the VIVs. Thus, the geometry of the bluff body has to be optimised to match the natural frequency of the convertor. This study examines the conceptual design of the physical model. The fluid–structure interaction model is applied to study the preliminary design. The maximum energy density that can be extracted by the proposed convertor from the water flow with velocities from 0.2 to 1 m/s is also estimated.Abbreviations: 1.CFD Computational Fluid Dynamics; 2.DC Direct Current (electricity); 3.FIM Fluid Induced Motion; 4.ODE Ordinary Differential Equation; 5.PTC Passive Turbulence Control; 6.VIV Vortex Induced Vibration; 7.VIVACE Vortex Induced Vibration Aquatic Clean Energy; 8.2D Two Dimensional     

电梯系统的节能与技术改造

电梯控制要求准确、安全,电梯运行中电动机有发电工况是客观存在.文章从电机学基础出发,分析了电梯的各种运行状态,指出在变频拖动中回馈制动的优越性,在现有变频器能耗制动的基础上,加装回馈单元是解决系统安全运行和节约电能的最佳途径.     

换流变压器阀侧用±204kV/2800A高压直流套管的研究

介绍了用于锦屏-苏南±800 kV特高直流输电工程同里换流站低端换流变压器阀侧±204 kV/2800 A高压直流套管的技术参数、主要尺寸、结构特点,研究的关键技术,型式试验及研究性试验的项目及试验结果。套管的额定直流电压为±204 kV,额定电流为2 800 A。主绝缘(电容芯体)为胶浸纸电容式,经内外绝缘优化设计、采用优质材料,通过工艺研究及试验验证,研制出产品并通过了型式试验及研究性试验的项目。产品的主要性能指标:工频耐受电压+局放测量289 kV(r.m.s),1 min工频耐受电压588 kV(r.m.s),雷电冲击耐受电压1 234 kV(peak),操作冲击耐受电压1 103 kV(peak),直流耐受电压+局放测量393 kVdc,极性反转+局放测量236 kVdc。     

自动扶梯节能运行改造方案浅析

在分析星三角驱动、全变频驱动、旁路变频驱动等自动扶梯节能运行改造方案优劣性的基础上,提出了采用一体化变频驱动进行自动扶梯节能改造的方案。对自动扶梯节能运行改造过程中相关国家标准的符合性问题也作了探讨。     

液力变矩器内部流场的三维数值模拟

液力变矩器内部的液体流动是一个非常复杂的三维流动问题.在液力变矩器设计和制造过程中,利用CFD(Computational Fluid Dynamics计算流体力学)从事设计和分析时,CFD数值模拟的精确程度与模型的建立和采取的数值方法、网格的划分以及边界条件的选择有关.为了考察这些影响因素,对典型的YB355-2型液...     

叉车液力变速器噪声源识别的试验研究

液力变速器的噪声水平是衡量内燃叉车质量的重要因素之一.对某型内燃叉车液力变速器进行分解试验,采集3种拆卸状况下液力变速器的振动、噪声信号,通过振动噪声频谱对比分析和噪声边频分析,验证了与液力变矩器同轴的齿轮的啮合激励是液力变速器的主要噪声源,为降低该系列内燃叉车液力变速器的表面辐射噪声提供有效的依据.     

Hierarchical modeling method and dynamic characteristics of cutter head driving system in tunneling boring machine

Traditional modeling method is difficult to establish the fully coupled model of the cutter head driving system in tunneling boring machine (TBM) owing to the structural complexity. In this paper, a generalized hierarchical modeling method is proposed to establish the entirely dynamic model of the TBM cutter head driving system. The components are equivalent to beam element with the same mass and stiffness characteristics, and the nonlinear coupling factors such as time-varying mesh stiffness, transmission error and gear backlash of both the multiple pinions driving and planetary gearbox are considered. The overall dynamic equation is formed by assembling the unit matrixes of basic finite elements according to the coupling relationships. Based on the proposed model, the vibration modes of driving system are classified into axial modes, rotational modes and lateral modes with distinct characteristics. The effects of coupling parameters on the natural frequency of driving system are investigated as well. The dynamic model is also simulated to analyze the dynamic response of driving system under two load conditions, cyclic external loads and simulated external loads. The main response frequency components and the effect of damping coefficients on vibration amplitudes are investigated. The proposed modeling method can be generalized to other complex driving system, and the obtained results provide data support for the dynamic design of driving system in TBM.     

时序方法在转炉模型谱分析中的应用

通过对转炉模型振动信号的测试,应用时间序列方法,建立了 ARMAV 模型.并由这一模型对所测数据进行了谱分析,从而得到了满意的结果.     

Quantitative driving rain exposure on a vertical wall at various Canadian cities

The quantitative driving rain exposure for 15 important Canadian cities is derived by making use of the climatological data recorded at local meteorological stations. The driving rain parameters, namely, precipitation, intensity, impact frequency and impact duration, provide both long term and short term characteristics of local driving rain exposure on a vertical surface. These driving rain parameters are useful to designers in designing tight building envelopes against rain penetration. A realistic driving rain exposure test environment can be simulated by making use of these quantitative results for evaluating the performance of the building envelope.     

Monitoring and Modelling

This reports interim results from monitoring a group of 15 low-energy houses in Manchester, UK, in order to assess the cost-effectiveness of different energy-conserving measures. It describes a system which provides economical monitoring with two levels of recording by mobile apparatus, and a simplified prediction technique which models the pattern of thermal behaviour, checked against field measurements. The method involves the use of a digital mini-computer connected to a passive electrical analogue circuit via digital-to-analogue convertors.