Accelerated life-test experiments on low-power rectifier diodes

Low-power rectifier diodes were stressed by different forward currents I_F, reverse voltages U_R, and ambient temperatures _a for a time interval (0, t*) in order to analyse the resulting distributions. Owing to the limitations in the test time, t*, the gathering of comprehensive information about their performance requires high stress levels without exceeding either physical limits or the limits for initiating thermal runaway. First, the results of lifetime experiments related to the middle stress region were described by a Weibull distribution with constant shape parameter and stress-dependent scale parameter. This model, however, did not fit sufficiently the typical features of the real-life distribution. Therefore a non-parametric measure called the average initial reliability in (O,t*) was defined using the experimental results. Its stress dependence was estimated. The results are guiding figures of stress conditions both for accelerated tests and for circuits with high demands on reliability.     

Theoretical study of molecular rectification in porphyrin dimer

Carrying out theoretical calculations using the density functional method for nonequilibrium electron transport, we investigated the electric conductibility of a porphyrin dimer coupled to gold electrodes by thiolate bonds. A porphyrin with four electron-donating amino groups in the dimer is connected to a porphyrin with four electron-withdrawing cyano groups by a dimethylene bridge. The calculations demonstrated that this dimer allows more flow of electrons from the first porphyrin (donor) to the second porphyrin (acceptor) than in the opposite direction. This means that the porphyrin dimer has favorable rectifier characteristics that are accounted for by the mechanism of not Aviram and Ratner [Chem. Phys. Lett. 29 (1974) 277] but of Stokbro, et al. [J. Am. Chem. Soc. 125 (2003) 3674].     

基于微控制器的晶闸管相序自适应电路设计

为保证三相桥式相控整流器的正常运行,同步电压与主回路电压的相序、相位必须匹配。本文通过研究晶闸管数字触发器的工作原理提出了一种利用线电压与相电压之间的相位关系通过TPL-521光耦,由单片机程序实现对电源相序和缺相的判断进而实现相序的自适应的方法。本装置不使用变压器或电压互感器而是直接从电源线接入,采集到的线电压过零点正好是相电压的自然换相点,容易实现控制角度与时间之间对应关系的计算。     

一种低压谐波抑制的新方法

介绍一种新的谐波抑制装置—通用滤波器UHF(UniversalHarmonicFilter)或线性滤波器(Lineator),它是无源滤波器领域里新的进展。它采用带有小容量滤波电容器的T型电抗器反极性接入电源与负荷之间。使得经过绕组中的反串互感减少了供电系统与非线性负荷之间的电压降落,同时,在谐波条件下供电系统支路形成一个高阻抗。这样,就使大部分谐波电流流入滤波器支路,而流入系统的谐波电流大大减少。使用SIMULINK,对装有UHF的三相六脉波整流器装置的工作特性进行数字仿真并与单调谐滤波器相比较,分析结果表明采用UHF对谐波有更好的抑制效果。     

基于可调式稳压器LM317的直流稳压电源

该设计主要利用可调式稳压器LM317实现直流稳压电源的正负输出可调性。整个电源主要由变压器、整流电路、滤波电路,以及稳压电路几部分组成。其体积小,稳定性好且性价比较高。主要介绍其具体实现及原理,并分析具体硬件电路的工作原理及具体实现方法。结合单片机原理以及其他相关集成电路模块的相关原理实现了直流稳压电源的显示等具体功能。经反复实验,结果表明其具有灵活的可调性,控制效果良好。该电源可广泛运用于电力电子、仪表、控制等实验场合。     

采用单片微处理器的一种新型数字式摩托车CDI点火性能测试台

本文对一种采用单片微处理器技术的新型数字式摩托车CDI点火性能测试台的工作原理及设计进行了详细的介绍。该测试台的主要部件及控制单元均采用单片微处理器构成的数字式单元仪表和部件，能满足对摩托车电气系统较高精度的测量要求。     

干熄焦提升控制系统的设计及应用

本文介绍了以干熄焦提升系统为例,阐述了系统的构成、功能及WINCC6.0在系统中的应用。     

龚氏桥式可控整流电路的研究

单相和多相桥式相控整流电路是教科书可控整流电路中的一大类性能最好的电路,也是社会上应用最多的一类电路,它在应用中给电网制造了大量感性电流和谐波电流,严重污染电网,影响电网供电质量。如何减少感性电流和谐波电流,成为电力电子基础电路和电源研究的重点。笔者在中国电源学会第20届学术年会上宣读的“导通角控制与熄灭角控制的复式可控整流电路研究”一文中对单相全波与桥式相结合的“龚氏桥全电路”已做了论述,笔者还将在上述研究的基础上对“龚氏桥式电路”和“龚氏半波电路”进行阐述,这样就构成一个完整的绿色相控电路体系,为“传统相控电源”向“绿色相控电源”转变提供理论和技术支持。     

Time stepping finite element analysis of a variable speed synchronous generator with rectifier

Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator’s behaviour.     

车用永磁发电机的设计研究

单相半控桥式整流稳压永磁发电机主要为车用直流电源及给蓄电池充电,采用钕铁硼永磁材料和对发电机的优化设计,提高了低转速时的输出电压.设计的单相半控桥式整流电子稳压器,集稳压、整流于一体,电能消耗少,使车用永磁发电机在变转速变负载工况下的输出电压保持稳定.