一种新型绝缘监测系统的设计

直流系统的绝缘性能直接影响直流回路的可靠性。针对监测电网直流系统的绝缘问题，提出了一种主-从式绝缘监测系统的设计方案，即用一个绝缘主模块来测量主回路的绝缘电阻，而用专门的支路模块来判断出现绝缘降低的那条支路，并利用不平衡电桥法给出了一个较为精确的，用于电网直流系统计算正负母线绝缘值都出现降低的情况下的正、负绝缘电阻的公式，在实际应用中取得了很好的效果，测量精度可达到5％。     

UJ26型低电势直流电位差计的按元件检定

UJ26型低电势直流电位差计(以下简称UJ26)属于0.02级电位差计。其简化线路如图1所示。由图1可知,调定工作电流的回路为并联回路,因此工作电流不仅与温度补偿盘支路有关,还与它相并联的支路电阻有关。     

一种用于舰船电力网络绝缘监测的弱电流传感器的设计

结合舰船电力网络绝缘监测装置进行支路电阻测量与故障支路判断时的需要，设计了采集漏电流信号的大口径弱电流传感器，并给出了试验数据，调离同的传感器已用于实际装置，试验运行状况良好。     

UJ33a工作电源的改进

UJ33a是测量精度为0.05级的携带式直流电位差计。广泛应用于实验室、车间及现场测量直流电压,亦可经换算后测量直流电阻、电流、功率及温度等。还可作标准电压输出,对电子自动电位差计、毫伏计等以电压作为测量对象的工业仪表进行校验。由于该仪器精度高、便于携带、用途广而颇受欢迎。UJ33a的工作电源为三节1号电池并联为一组,再两组串联为3V,根据设计要求,工作电源的电压允许范围为2.8～3.2V,若电池电压超过这个范围,工作电流就不能调至标准值3mA,这相当于单节电池用到1.4V以下就不能用了。故电池的使用效率较低。另外,由于电池容量有…     

逆变式方波交流电源工作原理的研究

本文阐述了可控硅逆变式电源的组成及工作原理,这种电源是由一般的直流焊接电源和一个可控硅逆变器组成的。分析了线路的工作原理及一些工艺参数对设备正常运行的影响。这种电源的交流电流频率和正负半波电流比值均可以分别调节,电源的主要技术参数是: 输入电压 380伏交流电流频率 2～100HZ 输出电流 20～300A 正负半波电流比例 0.3～0.7 空载电压 70伏负载持续率 80％这种电源可以不用采取任何外加稳弧措施,进行铝合金交流TlG焊,焊接高强度铝合金接头强度可以比一般电源焊接的提高10％左右。改变输出端的接线,这种电源也可以做为直流断续器使用,满足直流TlG脉冲焊的要求。     

直流稳压电源现场检定装置设计

本文主要介绍了直流稳压电源现场检定装置的组成及设计方案.通过设计直流电子负载、智能电网调整器、稳压电源自动检定装置,实现了直流稳压电源的电源电压调整率、负载调整率、输出电压短期稳定性、纹波电压、电压表、电流表示值误差的自动检定,提高了计量检定工作效率,解决了大功率直流稳压电源的现场保障问题.     

自制的直流毫伏发生器

该直流毫伏发生器主要用来配合直流电位差计检测以热电偶作传感器的动圈式指示调节仪表、电子电位差计、电子平衡电桥等温度控制仪表等。下图为我们自制的直流毫伏发生电路原理图。工作原理是,开关 K 闭合后,4.5V 直流电源经粗调电位器 W_1形成回路,通过最小值为6mA 的工作电流,使电源电压稳定;从粗调电位器 W_1的可调端取出的工作电压,经细调电位器 W_2和微调电位器 W_3调节     

二次压降在线监测系统在变电站中的技术应用及研究发展方向

采用在变电所计量屏和电力大用户计量回路中加装“二次回路压降自动监测装置”,该装置不仅能够实时监测二次回路压降,且能够通过微机系统的计算分析得到数表及曲线方式进行存储。借助计算机网络和通信技术可以将处理过的数据在后台上可得到展示,为计量管理人员提供判断依据,通过电压降的变化情况判断电压互感器一次及二次回路是否断线,计量屏PT电压切换继电器触点是否氧化,二次电压回路端子接触是否良好,实现二次电压降值超标报警的功能。数据可以发布到公司MIS网,供管理人员和计量人员实时监测。     

KZC—磁控溅射镀膜机电源的研究

本文介绍KZC—磁控溅射镀膜机电源的组成，工作原理和具有自动起动功能及抑 制系统振荡的良好动态特性。文中详述了“自适应电流调节器”、“电流截止负反馈”、 “触发电路”、“给定积分器和电压调节器”。该电源为磁控溅射镀膜设备实现自动控制 提供了方便。     

电源波形对电镀质量的影响

1.前言电镀电源通常使用直流电源,也用市用交流电整流的直流电源。严格地说,这种电源供电的电流不叫直流,而叫作脉动直流。目前,具有可控整流特性的可控硅整流器不是调节输入电压来控制输出电压和电流(通常的整流器是控制输入的交流电压变化其输出电压),而是在整流的同时,将其输出波形     

敏感用户高品质交-直流级联供电方案研究

工业过程中大量使用的变频器(variable frequency drive,VFD)在采用传统交流供电时易受到电压暂降影响,传统治理方式存在检测延时、控制复杂等问题。为此,该文从敏感负荷变频器在电网扰动工况下的供电需求量化出发,围绕供电拓扑设计、DC/DC变换器的控制策略及储能单元容量配置等方面,构建一种实用化工业用交-直流级联供电方案。该文利用电压暂降过程中直流供电回路与敏感负荷间的压差自感应控制,实现交-直流供电回路无扰动切换,提高电压暂降治理响应的快速性;采用两相交错并联DC/DC变换器接入集中式储能,减少储能系统纹波系数,并给出两相均流控制方法。最后,通过Matlab/Simulink中的建模仿真与样机的实验测试,验证所提方案能够在交流系统发生不同严重程度电压暂降过程中为各类敏感负荷提供稳定的连续供电,为解决工业敏感用户高品质供电问题提供可实用的新思路。     

直流高压标准装置国际近况

简单介绍电磁计量领域关键比对数据库中直流高压参数标准装置-直流高压分压器的原理,分析了电阻发热、电晕放电以及绝缘支架漏电对直流高压分压器的影响,归纳总结目前国际上先进计量机构的直流高压标准装置的结构型式以及在校准时引入的不确定度来源。给出了直流分压器达到10-6量级的必要条件。     

Ultra low-noise current sources

The solid state DC current sources available on the market are not suitable for applications in low noise measurement systems because of the high level of low-frequency noise introduced in the measurement chain. The most important cause of low-frequency noise in such instruments is the solid state device used as a voltage reference (usually a Zener diode). This problem has been solved, in the instrument described in this paper, by using a new circuit topology in which the solid-state voltage reference has been substituted by a low-noise battery. The instrument, capable of supplying a current as high as 100 mA, is characterized by a low-frequency noise level some orders of magnitude lower than that of similar commercial instrumentation     

Integrated power management circuit for piezoelectronic generator in wireless monitoring system of orthopaedic implants

Piezoelectric (PZT) materials are capable of converting the mechanical energy of compression into electrical energy. With the recent advent of extremely low-power electrical devices, PZT generators have become attractive in many kinds of applications, especially for biomedical applications. Piezoelectronic generators are used in a wireless monitoring system of orthopaedic implants. Due to their poor source characteristics, the efficiency of PZT generator is low. A hybrid direct current (DC)?DC, comprising a switched capacitor (SC) DC?DC converter and a low dropout (LDO) linear voltage regulator, is presented to improve conversion efficiency. A bandgap reference (BGR) circuit which works in sub-threshold region is also presented. Because SC DC?DC converter works in the highest voltage region in this system, small power supply current, including supply current through BGR and other auxiliary modules, means low power consumption. BGR?s power supply voltage can be varied from 3 to 16 V. Its supply current is only 3.2 μA at 125 C and its temperature coefficient is 46 ppm. Stacked switches technique is proposed to reduce leakage current in switching process of SC converter. Simulation results show that the efficiency of SC?s converter can reach 88%, that of LDO can reach 80% and that of the overall system can reach 66%, including power consumption of all auxiliary components, which is far higher than previous work.     

直流高压电阻分压器泄漏电流测量研究

介绍了一种测量直流高压电阻分压器泄漏电流的装置。该装置采用ZigBee无线通信技术,通过独立电源供电的方式,避免了因高压电场导致测量仪器损坏的风险,解决了分压器在高电压工作状态下难以测量泄漏电流的问题。通过采用同步采样的方法,有效克服了高压电源纹波和漂移对测量精度的影响,泄漏电流测量不确定度优于9.8×10^-6 V,k=2。     

Novel zero voltage switching dual-switch forward converter with ripple current cancellation

A zero voltage switching (ZVS) dual-switch forward converter with ripple current cancellation is presented. In the proposed converter, active clamp circuit is used to clamp the voltage stresses and to realise ZVS of all switching devices. Active clamp boost converter with power factor correction is used in the front stage of the proposed converter to draw a sinusoidal line current from the AC source and to maintain a constant voltage at the DC bus. The second stage of the proposed converter is a dual-switch forward converter with current doubler rectifier to obtain the isolated low output voltage. Active clamp circuit used in the DC/DC converter can recycle the energy stored in the leakage inductor and magnetising inductor so that the voltage stresses on the switches are limited and the ZVS feature is realised. The current doubler rectifier offers the ripple current cancellation at the output capacitor and reduces the current stress of the transformer secondary winding. The circuit configuration and principle of operation are analysed and discussed in detail. Experimental results with a laboratory prototype based on a 90-260 V_rms input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter.     

太阳电池填充因子随日照强度变化的理论分析与计算

根据太阳电池直流模型和最大功率点数学条件,推出短路电流、开路电压、最大功率点电流和电压 以及填充因子随日照强度变化的数学关系式;并选取２个电池分别计算出在不同日照强度下上述电池参数随日 照强度的变化率。验证了短路电流和最大功率点电流是近似跟日照强度成正比,开路电压和最大功率点电压是 近似跟日照强度的自然对数成正比。并提出了填充因子随日照强度的变化关系不具有简单的函数形式,而对不 同的太阳电池其变化关系也迥异。最后用Multisim的模拟结果检验了理论分析计算的正确性。     

论电子式直流电能表实行强制检定的必要性

由直流电流(或代表直流电流的电压)和直流电压作用于固态(电子)元件而产生与被测电能成正比输出的仪表,称为电子式直流电能表。通过对电子式直流电能表的计量检定,加强了直流电能、直流功率测量技术和测量方法的研究,推动了整体质量的不断提升。     

脉冲调宽乘法器在交流应用下的误差及标准功率、电压、电流测量仪的研制

本文讨论了脉冲调宽乘法器用于交流测量时交直流变换误差与时分割频率的关系，提出了一种新的准确计算方法，并对相移误差等因素作了分析，给出了减小误差的措施。最后介绍了基于上述分析而设计研制的标准功率、电压、电流测量仪，其测量功率、电压、电流的误差均小于００１％     

Noncontacting low-cost instrument for film thickness measurement

A low-cost, noncontacting, nondestructive technique is presented for measuring the thickness of thin liquid or solid films and coatings in real time by utilizing the resonance properties of microstrip structures. A new measurement system in which all the microwave components are internal to the instrument, thereby eliminating the need for microwave test equipment, is described. Only a low-voltage DC source, such as a battery, is required to power the unit; the output is also a DC voltage or current. Using a linear model, sample coefficients of determination, r², greater than 0.98 have been obtained for film thickness measurements of water, enamel paint, and silicon rubber up to 0.8-1.5- and 2-mm thick, respectively. Copper sheet metal up to 0.9-mm thick has been measured with an r² greater than 0.99. The measurement range can be extended or improved even further if nonlinear circuit behavior is accounted for