开关电源电磁干扰抑制分析

开关电源的电磁干扰对电子设备影响很大。本文针对开关电源工作的不稳定性,分析了开关电源电磁干扰产生的原因,提出了抑制电磁干扰的措施,最后列举了几种最新的抑制电磁干扰电路,并对其工作原理做了分析。     

开关电源抗电磁干扰的研究与分析

电磁干扰对电子设备的性能有很大的影响,首先分析了开关电源电磁干扰产生的机理,提出了几种有效的抑制开关电源电磁干扰的措施。重点阐述了滤波技术在抑制开关电源电磁干扰方面的作用,设计了具体的滤波电路并通过实验测量对结论加以验证。     

开关电源电磁干扰分析及抑制

开关电源由于本身工作特性使得电磁干扰问题相当突出。从开关电源电磁干扰的模型入手论述了开关电源电磁兼容问题产生的原因及种类，并给出了常用的抑制开关电源电磁干扰的措施、滤波器设计及参数选择。     

开关电源抗电磁干扰的研究与分析

开关电源在各个领域都得到了广泛应用,但其电磁干扰对电子设备的性能有很大影响,因而在一定程度上限制了它的应用。本文首先介绍开关电源产生电磁干扰的机理,然后分析开关电源电磁干扰的几种有效抑制措施。     

频率扰动法降低开关电源电磁干扰的试验研究

采用一种开关电源控制方法——开关频率扰动方法来降低开关电源电磁干扰进行了试验研究。试验结果表明,采用该方法后,开关电源电磁干扰幅值得到明显降低,最大降幅超过8dBμV,平均降幅5dBμV。试验研究结果证实,开关频率扰动方法能够有效降低开关电源的电磁干扰水平。     

无源滤波器在开关电源中的应用分析

高频开关电源的传导性电磁干扰是电力电子装置的主要干扰源之一．国际电磁兼容法规定的电源产品的EMC指标已成为开关电源的一个极为重要的性能参数．正确分析开关电源的电磁干扰和采用适当的滤波措施是开关电源设计的前提。运用开关电源传导性电磁干扰模型，对开关电源的传导性电磁干扰机理做了全面的分析．提出一种采用无源滤波器技术来减小开关电源电磁干扰的方法。同时，引入无源滤波器插入损耗的概念．推导出高性能无源滤波电路的差模干扰与共模干扰模型．并依据无源滤波器对干扰信号的插入损耗最大原则设计开关电源输入端无源滤波器。应用结果表明．所提出的无源滤波器对开关电源高频段的电磁干扰有很好的消除效果。     

浅析开关电源的电磁干扰(EMI)及其抑制措施

对开关电源产生电磁干扰的机理进行了简要介绍,总结了几种主要的抑制开关电源电磁干扰的方法。     

开关电源的电磁干扰及抑制技术

开关电源是常见的电磁干扰源,其干扰信号经传导和辐射对电子设备、通信系统等产生电磁污染。通过对电磁干扰产生的机理描述,着重分析了开关电源电磁干扰产生的原因,并有针对地总结了几种抑制电磁干扰的技术方法。     

开关电源的干扰及其抑制

开关电源本身产生的干扰直接危害着电子设备的正常工作。抑制开关电源本身的电磁噪声，是开发和设计开关电源的一个重要课题。简要地对开关电源电磁干扰产生、传播的机理进行了介绍，总结了几种主要的抑制开关电源电磁干扰产生及传播的方法。     

开关电源的电磁干扰及抑制技术

由于开关电源本身的工作原理,使得电磁干扰问题相当突出,其干扰信号经传导和辐射对电子设备、通信系统等产生电磁污染。本文从电磁干扰产生的机理入手,着重分析了开关电源电磁干扰产生的原因,总结了抑制电磁干扰的措施,比如滤波、屏蔽、接地等。     

高速异步电动机转轴的疲劳特性分析

基于Ansys多物理场仿真软件平台,对高速异步电动机的转轴进行疲劳特性分析,校核高速异步电动机转轴的疲劳强度和高速运行的可靠性,预测电机转轴的寿命;分析电磁力对转轴疲劳寿命的影响,判断疲劳特性的类型。对比分析作用于电机结构的电磁力波频率、幅值和电机转轴各阶模态的固有频率,校核电机转轴的强度。在转轴不会因电磁振动发生断裂的前提下,将电磁力等效为静应力分析转轴的疲劳特性,校核电机轴在电机寿命周期内是否会发生短周疲劳损坏;并采用凹圆角设计进一步提高转轴的结构可靠性,提高电机的转轴寿命。     

交联聚乙烯交联度对材料击穿强度的影响

为了研究XLPE材料交联度对其电气性能的影响,制备不同交联度的XLPE样本并对其进行电气击穿实验,分析在不同的交联度区间范围内样本击穿场强变化。利用温度-时间控制法制备六组不同交联度的XLPE样本;利用差式扫描量热仪测量得到样本结晶度;利用交流变压器测量得到样本的击穿强度。实验结果表明,随着交联度上升,样本击穿场强呈先上升后下降趋势。在交联度为0%～75%区间范围内,样本击穿场强增加2%。在交联度为75%～88%范围内,样本击穿场强增加21.2%。而在交联度为88%～92%范围内,样本击穿场强下降5.3%。分析认为,样本的击穿强度与样本交联度和材料均匀程度有关。当交联度较低时,样本的击穿强度主要由样本交联度决定,随着交联度上升,样本击穿强度增加。但由于此时局部材料结构较为不均匀,因此击穿强度增加幅度不大。而当交联度上升至75%时,材料形成较为密集、均匀的三维网状结构,导致样本击穿场强大幅上升。而当交联度继续增加时,此时样本结晶度下降幅度较大,局部材料结构变得不均匀,导致样本击穿强度下降。     

特高压电晕笼防护段的设计

为了克服特高压电晕笼设计中电晕笼两端部的电场畸变,确保电晕特性测试准确有效,需要增设一定长度的防护段。采用三维有限元方法精细计算了电晕笼内导线表面电场分布,分析了导线弧垂对防护段长度的影响并提出了新颖的电晕笼防护段设计方法。计算说明新型结构的防护段能有效平滑和抑制电晕笼端部附近导线表面电场的畸变,使电晕笼内导线表面电场更趋于一致,提高了电晕特性试验的准确性。     

最小曲率法与峰值检测相结合的纸张计数算法

为解决叠层纸张计数的难题,提出了一种最小曲率法与峰值检测相结合的叠层纸张计数算法。首先,从叠层纸张图像中沿垂直纸张方向依此逐行提取灰度剖面,经高斯滤波后计算其曲率值。接着寻找叠层纸张的中心点,由于纸张的灰度剖面图呈高斯形状,所以局部极小曲率点是纸张的中心位置点,并且曲率连续0的宽度为一张纸张的厚度。然后,利用相邻中心位置点之间的距离以及相应点的灰度信息对纸张中心点位置进行校正。最后,利用峰值检测对脊线结果进行计数。本文算法通过融合纸张灰度特征与相邻纸张距离能准确检测异常纸张。实验证明,对于厚度在0.05~0.2 mm的叠层纸张的计数误差都小于0.01%。     

A Study of the Absorption of Nitrogen Oxides from the Boiler Flue Gases

In the past decade, the number of unsolved ecological problems has been steadily increasing. Among the numerous causes of this situation, the exposure of the environment to industrial waste should be mentioned. For example, enterprises of the fuel and energy industry emit a significant amount of hazardous substances into the atmosphere. Flue gases formed in boiler-houses and at thermal power stations get through flue gas stacks into the upper atmosphere and pollute it. In this work, a method is proposed for adsorption treatment of the flue gases from boilers fired with associated petroleum gas. The chemical composition of the associated petroleum gas of Romashkino oil field, the Republic of Tatarstan, is presented and the practicality of its use is demonstrated. Nitrogen oxides contained in the boiler flue gases result from oxidation of molecular air nitrogen during combustion of the fuel. In order to reduce the adverse effect of hazardous substances on the environment, the flue gases are to be compulsorily cleansed of nitrogen oxides. The use of the sludge resulting from coagulation and liming of natural water during the chemical water treatment at Kazan CHPP-1 as a sorption material is proposed. The chemical composition and technical characteristics of the sludge are presented. The properties of the sludge were studied using a laboratory fixed-sorbent-bed setup. The sorption capacity and water-absorption of the sludge were determined and curves of the kinetic and isothermal dependences of the nitrogen oxide adsorption by the sludge were constructed. The change in the nitrogen- oxide sorption capacity of the sludge depending on the sludge particle size was established. The optimal characteristics of a batch-type fixed-bed absorber were calculated. The results of calculating the economic and ecological effects of introducing the adsorption treatment of flue gases to remove nitrogen oxides for the boiler-house of AO Karpov Chemical Plant are provided.     

Considering the summation of the effect of harmful substances during the calculation of the environmentally safe waste water discharge

This article presents the technique of assessing the maximum allowable (standard) discharge of waste waters with several harmful substances into a water reservoir. The technique makes it possible to take into account the summation of their effect provided that the limiting harmful indices are the same. The expressions for the determination of the discharge limit of waste waters have been derived from the conditions of admissibility of the effect of several harmful substances on the waters of a reservoir. Mathematical conditions of admissibility of the effect of wastewaters on a reservoir are given for the characteristic combinations of limiting harmful indices and hazard classes of several substances. The conditions of admissibility of effects are presented in the form of logical products of the sums of relative concentrations that should not exceed the value of 1. It is shown that the calculation of the process of wastewater dilution in a flowing water reservoir is possible only on the basis of a numerical method to assess the wastewater discharge limit. An example of the numerical calculation of the standard limit of industrial enterprise wastewater discharges that contain polysulfide oil, flocculant VPK-101, and fungicide captan is given to test this method. In addition to these three harmful substances, the water reservoir also contained a fourth substance, namely, Zellek-Super herbicide, above the waste discharge point. The summation of the harmful effect was taken into account for VPK-101, captan, and Zellek-Super. The reliability of the technique was tested by the calculation of concentrations of the four substances in the control point of the flowing reservoir during the estimated maximum allowable wastewater discharge. It is shown that the value of the maximum allowable discharge limit was almost two times higher for the example under consideration, taking into account that the effect of harmful substances was unidirectional, which provides a higher level of environmental safety for them.     

基于复杂网络的产品竞争网的特性研究

专业镇经济是珠三角经济的重要特征之一,本文对以同类和关联产品为纽带的专业镇经济,从复杂网络的角度进行了分析.在专业镇企业集群的产品竞争网构建方面,提出了一个新颖的竞争选择度模型.通过基于竞争选择度模型的专业镇产品竞争网的建模分析,可以发现珠三角专业镇的产品竞争网具有比较典型的无标度和小世界特征.经过对广东顺德地区2个国内比较著名的专业镇产品竞争网的实证分析,可以大致得出与产品竞争网理论推导相符合的结论.     

220kV GIS隔离开关触头烧坏故障分析与对策

探讨220kV振林变电站GIS隔离开关动触头对外壳内壁放电导致绝缘击穿的原因。对20546隔离开关故障相气室进行解体检查,并采用X光透射技术对站内其它同批次的220k V隔离开关动触头分闸位置进行检测。根据检测结果分析,20546隔离开关气室故障原因为隔离开关动触头分闸不到位,造成电场畸变,从而导致动触头绝缘击穿。对20546隔离开关驱动轴进行调整后,故障相动触头分闸不到位问题得到解决。针对该变电站隔离开关动触头分闸不到位问题提出了控制措施。     

Electrostatic Current Generator Having a Disk Electret as an Active Element

An electrostatic current generator having a disk electret as the active element is described. The electret consists of two oppositely polarized half-disks producing an electric field normal to the plane of the electret. The electret constitutes the rotor of the generator and is located between two pairs of conducting half-disks which constitute the stator of the generator. The field of the electret induces charges on each half-disk of the stator. The magnitude and polarity of these charges at any given time are determined by the angle formed at this particular time between the plane separating the two halves of the electret and the plane separating the half-disks of the stator. When the half-disks of the stator are appropriately connected through an external circuit, an ac current is produced. The order of magnitude of the peak value of the current is given by I ? ?e?S where ae is the effective surface charge density of the electret, S is the total area of the flat surfaces of the electret, and w is the angular velocity of rotation of the electret.     

避雷针迎面先导发展物理过程仿真研究

开展避雷针迎面先导起始及发展过程的仿真研究对建立正确的雷电屏蔽分析模型具有重要意义。基于长间隙放电的物理机制,建立了包括正极性电晕起始与流注发展、先导起始、先导–流注体系发展等物理过程的迎面先导发展物理过程仿真模型,并使用实验室和自然雷电条件下的迎面先导发展过程观测结果对其进行了验证,最后采用该模型对避雷针迎面先导特性进行了分析讨论。结果表明:该模型的计算结果与实验室条件下和一次自然雷电条件下获得的正极性迎面先导发展过程观测结果相吻合;迎面先导起始时刻随着雷电流幅值和避雷针高度的增加而提前;避雷针迎面先导的发展过程主要受雷电流幅值、避雷针高度影响,其发展速度随着下行先导的趋近而逐渐增加;由实验室条件下的正极性棒–板间隙放电获得的先导起始特性直接用于自然雷电中正极性迎面先导起始的计算,以及在迎面先导发展过程的计算中假设迎面先导发展速度与下行先导发展速度成一固定比例是不合适的。