变压器设计的图解法

对广大电子爱好者说来,经常为无法购得适当的变压器而大伤脑筋。许多优秀的电子设计套件由于不配适当的变压器,而使电子爱好者一筹莫展。 这里讨论的变压器设计法是以诺模图(nomogram)为基础的,设计过程快速、简便。通常设计一个变压器要不了五分钟。 第一个诺模图有四个轴,即左、右、上和下,分别代表参数为圈/伏、二个绕组的窗口面积、变压器的瓦数     

10KV配电变压器的运行维护

本文从新安装或大修后的配电变压器投运前的检查验收、配电变压器的正常巡视检查、配电变压器的特殊巡视检查项目、干式配电变压器的运行检查四个方面阐述了10KV配电变压器的运行维护。     

变电站多主变并列运行经济性探讨

本文通过分析变压器的技术参数，如变压器的损耗原理和经济运行系数对变压器的经济运行方式做出选择，最后通过实例分析论证了变电站多个变压器并列运行的经济性。     

《电机与变压器》课程教学方法探讨

《电机与变压器》这门课程是技校学生的一门专业课,非常重要,但是在教学过程中,学生基础差,学习的热情不够,教师教学存在许多不足,教学有待反思。现从教学安排、教学方法、教学手段、实验实践、学习方法五个方面进行探讨分析,以提高教师教学效率和学生学习的能力。     

浅析非晶合金变压器在通信局房的应用

随着通信技术的迅猛发展,节能减排已成为通信业务发展的一个重要方面。非晶合金作为铁心的非晶合金干式变压器属于新型节能变压器,文章介绍了非晶合金铁心变压器及其铁心材料的特点和性能,通过对通信局房的各应用场景的数据分析,反映出非晶合金干式变压器在节能减排方面的显著效果。     

变压器耦合固态刚管调制器的窄脉冲应用

当前研制固态刚管调制器已经是雷达发射机技术的重要发展方向,不论是直接耦合还是变压器耦合的固态刚管调制器,在许多新型雷达发射机中都得到了应用。文中从开关器件的选择和变压器分布参数两个方面,对变压器耦合固态刚管调制器在窄脉冲应用时的输出波形进行了分析,通过分析和一些验证试验,得到了控制脉冲前沿和过冲的方法。     

浅析电力变压器高压试验研究

通过对电力变压器的简述和高压试验的简述，说明电力变压器高压试验的重要性，并具体从温度和湿度、电压极性与泄漏电流关系、升压速度等几个因素分析对电力变压器高压试验影响，并对高压试验采取的安全措施和使用变压器的注意事项等进行具体的阐述。     

变压器电阻接地技术的优势分析

在整个电力系统中,变压器中性点电阻接地方式涉及到经济和技术方面的问题。为了能够对变压器的电压安全,必须要通过变压器电阻接地技术的运用,以来对电压进行有效的控制。下面本文就对变压器中性点电压接地技术的优势进行分析。     

关于地下变压器冷却系统的分析

文中通过分析当前地下变压器冷却方式存在的不足和问题,按照变压器安全运行生产要求,结合设施环境噪声限制,综合当前各类冷却方式的优点,提出了地下变压器分步式冷却方式。通过两个相互独立的油流冷却系统散热,从而克服当前地下变压器冷却方式的缺点,有效地解决当前地下变压器的冷却问题。     

电力变压器温控器校准辅助系统的优化方案研究

文章通过对电力变压器温控器校准辅助系统在电力变压器温控器实际校准工作中的实践应用分析,从实用性、高效性、可操作性等几方面反复验证和推敲,进一步提出电力变压器温控器校准辅助系统的优化方案,为设计出更加智能、高效、完善、操作方便的温控器校准检测系统提供参考。     

Compensation of errors in a voltage transformer by an electronic circuit

An automatic self-compensating technique for instrument (voltage) transformers has been presented. With the introduction of such an electronic compensator, even ordinary voltage transformers may behave with high accuracy and precision. Analytical and experimental results show that the compensator brings down the ratio and phase angle errors significantly. The arrangement presented is simple, but constitutes a definite modification of existing methods used for error compensation.     

阻抗匹配器级数对铁电体移相器性能的影响

针对铁电体透镜式移相器的阻抗失配问题,分别采用3级、4级和5级的1/4波长阻抗匹配器结构,对铁电体移相器进行阻抗匹配调试仿真。通过对比不同匹配级数的匹配效果,最终确定了4级的匹配方案,并通过进一步优化器件结构,设计出的铁电体移相器在X频段内可实现360°相移,驻波比在主带宽内小于1.2,反射系数大于20 dB,中心频率处反射系数达到40 dB,信号传输系数在低频处小于1.1 dB,在高频处为1.5 dB,实现了铁电体移相器较好的阻抗匹配。     

一种基于LEACH路由协议的改进算法

无线传感器网络的生存时间受传感器节点软硬件条件的限制,改进传感器网络路由协议是延长网络生存时间的有效途径。LEACH协议是最早提出的经典分层路由协议,文中基于LEACH协议提出改进,应用K-medoids算法改进LEACH协议的簇首分簇机制,并通过Matlab仿真实验,证实了改进后的LEACH算法在均衡化网络能耗,延长网络的生命周期方面具有优越性。     

Useful time-variable circuit-element equivalences

Because time-variable circuit elements have properties not possessed by time-invariant ones, such as the ability to modulate or amplify with low noise, it is useful to have different ways of looking at them. Here we present general equivalences for time-variable inductors, capacitors, resistors and gyrators, using time-invariant elements and time-variable transformers, which allow various properties to be determined and interpreted on physical grounds.     

Multicell Interleaved Flyback Using Intercell Transformers

An original converter composed of interleaved flyback is presented. The cells are interconnected through intercell transformers replacing the standard multi-winding inductors used as insulation and storage magnetic device in the flyback. The combination of the interleaving effects and of the intercell transformer characteristics allows eliminating the mains limitations of the standard flyback due to the low performances of multiwindings inductors. In a first part, the different ways to interleave galvanic insulated converters as forward or flyback are briefly recalled. The second part presents the intercell transformers and shows that they can be used to interconnect interleaved converters cells. In the third and last part, this particular magnetic interconnection is applied to interleaved flyback cells and leads to create an ldquointercell transformer flybackrdquo. Its specific properties and advantages are described. Experimental results, obtained on a 2-kW test bench are finally presented.     

Thermal Simulation of Underground Power Distribution Transformers

This paper presents the differential equations that model the heat flow of power transformers located in underground vaults. The solution procedure results in the hot spot winding temperature and its time variation through the daily load cycle. A set of simulations is carried out to evaluate the transformer's thermal behavior during overload and contingency conditions. In such simulations the loss of life is estimated to objectively evaluate the technical and economical performance of the power transformer. The air flow in the ventilation system is considered, to search the optimal conditions of heat transfer to the external environment. The paper also considers the conditions in which the forced ventilation system can be switched off.     

Reducing code wastage in orthogonal variable spreading factor‐based wideband code division multiple access networks

Most third‐generation and beyond wideband code division multiple access networks use the orthogonal variable spreading factor code tree for channelization codes. The codes in this code tree are limited and the performance of a wireless network depends upon the code assignment for new calls. In this paper, we introduce a term called ‘wastage capacity’, which gives us the amount of wastage caused when a code (single or multiple) with a data rate higher than the rate of the incoming call is assigned to it. We suggest two methods to keep wastage capacity below an arbitrary threshold value or zero. In the first method, we devised an algorithm in which wastage up to a certain threshold would be tolerated and the minimum rakes to get this wastage capacity were identified. In the second approach, we reduced the wastage capacity to zero irrespective of the number of rakes at the expense of higher cost and complexity. Copyright © 2011 John Wiley & Sons, Ltd.     

A new passive 28-step current shaper for three-phase rectification

A new passive 28-step current shaper for three-phase rectification is proposed in this paper. With a phase-shifting transformer on the AC side and six interphase transformers on the DC side, per-phase input current can be shaped into a 28-step sinusoidal waveform. The total harmonic distortion of AC input currents obtained is 6.53%, lower than one-half of that in a conventional 12-pulse converter. The transformer voltampere rating is also lowered down to one-fifth of that in a 12-pulse converter. A 2 kW experiment is performed to verify the proposed circuit.     

Novel soft-switching DC-DC converter with full ZVS-range andreduced filter requirement. I. Regulated-output applications

A novel soft-switching topology for DC-DC converters is proposed. It is well suited for applications in the range of a few hundred watts to a few kilowatts. It is essentially a hybrid combination of an uncontrolled half-bridge section and a phase-shift controlled full-bridge section, realized with just four switches. The main features of the proposed topology are zero-voltage-switching down to no-load without serious conduction loss penalty, constant frequency operation and, near-ideal filter waveforms. The improved filter waveforms result in significant savings in the input and output filter requirement, resulting in high power-density. The new topology requires two transformers and two DC-bypass capacitors. The combined VA rating of the two transformers is more than that of the single transformer of conventional full-bridge converters, for variable-input applications. In Part I of the paper, the converter operation is analyzed for typical switch-mode power supply applications, where the input voltage varies widely but the output voltage is fixed and is well regulated. Experimental results obtained from a 100 W/200 kHz proof-of-concept prototype confirm the superior features of the proposed hybrid configuration     

光纤干度测量技术在注汽式油井参数测量中的应用

阐述了光纤干度传感技术用于注汽式油井干度测量的原理与方法,设计了一种新型的能够井下实时测量的油井参数采集和处理系统。该系统充分利用C8051F410功耗低、速度快、体积小和功能强大的特点,使得系统小巧、轻便并能在高温高压环境中安全正常工作。多次试验结果表明该系统性能稳定,测量准确。给出软件的设计思想和方法。