电力变压器短路承受能力试验相电流精确测量方法

介绍了变压器短路试验的基本情况和标准对短路试验相电流测量的规定要求。针对目前三角形联结绕组的变压器相电流无法直接测量的问题,提出了一种等效线路测量方法。通过公式推导和理论计算,搭建电路图,实现动态系统建模、仿真和分析,并对此测量方法进行了应用验证。所提测量方法符合标准要求,且提高了检验效率和测量精度,保证了检测的公正性和故障定位的有效性,具有一定的推广和借鉴意义。

电力变压器短路承受能力试验相电流精确测量方法浅析

变压器的短路承受能力是指变压器在短路冲击下能承受的最大短路电流的能力,也就是在一定时间内,在额定短路电流作用下,变压器绕组和铁芯所能承受的最大短路电动力。目前,我国变压器制造厂对电力变压器进行短路试验时,通常采用测量绕组电流来进行,但由于绕组电流是以其本身的负载电流为参考而制定的,受绕组三相电流不平衡、相序不正确等因素影响,往往使测量结果偏离实际值。因此,准确测量变压器绕组相电流是保证变压器运行安全的重要环节。本文从理论上分析了在正常运行和检修时测量绕组电流时误差产生的原因及其影响因素,并提出了解决方案,以保证试验结果的准确性。同时提出了一种新的测量方法全周期法。

三相电机驱动系统相电流检测技术的现状以及未来发展趋势

三相电机驱动系统中相电流测量方法是影响伺服电机驱动系统成本和性能的一个重要因素。如何能够在不过多失去精度的要求下,尽可能的减少成本是目前工业界的追求目标。因此在三相驱动器低成本要求的驱动下,学者们提出了多种针对不同需求,不同场合各具特色的相电流测量方法。将这些方法根据其相似特性划分为两大类,分别从最低成本的使用单个采样电阻/传感器的相电流测量方法和3个采样电阻的相电流测量方法出发。首先总结了这些方法的实现原理,然后分析它们各自的特点以及相应存在的局限性,并针对这些局限性提出可能改进的方向,最后通过对系统自身的分析,对未来的三相电机驱动系统内的低成本相电流测量技术的发展趋势进行了讨论和展望。

一种集成CAN总线的步进电机驱动装置

采用dsPIC30F6010A高性能数字信号控制器,提出并实现了一种新型的集成CAN总线接口的步进电机驱动装置。根据dsPIC30F6010A芯片外设模块的参数特点,设计了PWM驱动电路、电机相电流测量电路和CAN总线收发器电路,开发了基于C语言的模块化应用程序。实际测试表明,该集成CAN总线的步进电机驱动装置可以直接接入CAN总线网络,实现了对电机运行参数和运行状态的远程控制功能。

Characteristics of a Flow Transducer Based on Polarized Charge

In this paper we analyze the characteristics of a flow transducer based on polarized charge. The effects of the charged particles in pneumatic pipeline on the measurement pipe potential are discussed in detail and the equivalent circuits of the potential measurement are presented. On this bases, the relationships between mass flowrate and the electrical potential are obtained for different time constants of the measurement circuit. A satisfactory model is presented based on the characteristics of gas solid two phase flow. The linearity of the model is verified by the experiment results. The transducer, which is coaxially connected with the transport pipeline, does not disturb the flow state and has the features of ruggedness and durability, it is especially suitable for industry process control.

Design of Parallel Electrical Resistance Tomography System for Measuring Multiphase Flow

ERT(electrical resistance tomography) is effective method for visualization of multiphase flows,offering some advantages of rapid response and low cost,so as to explore the transient hydrodynamics.Aiming at this target,a fully programmable and reconfigurable FPGA(field programmable gate array)-based Compact PCI(peripheral component interconnect) bus linked sixteen-channel ERT system has been presented.The data acquisition system is carefully designed with function modules of signal generator module;Compact PCI transmission module and data processing module(including data sampling,filtering and demodulating).The processing module incorporates a powerful FPGA with Compact PCI bus for communication,and the measurement process management is conducted in FPGA.Image reconstruction algorithms with different speed and accuracy are also coded for this system.The system has been demonstrated in real time(1400 frames per second for 50 kHz excitation) with signal-noise-ratio above 62 dB and repeatability error below 0.7%.Static experiments have been conducted and the images manifested good resolution relative to the actual object distribution.The parallel ERT system has provided alternative experimental platform for the multiphase flow measurements by the dynamic experiments in terms of concentration and velocity.

Liquid holdup measurement with double helix capacitance sensor in horizontal oil-water two-phase flow pipes

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.

The Velocity Measurement of Two-phase Flow Based on Particle Swarm Optimization Algorithm and Nonlinear Blind Source Separation

In order to overcome the disturbance of noise,this paper presented a method to measure two-phase flow velocity using particle swarm optimization algorithm,nonlinear blind source separation and cross correlation method.Because of the nonlinear relationship between the output signals of capacitance sensors and fluid in pipeline,nonlinear blind source separation is applied.In nonlinear blind source separation,the odd polynomials of higher order are used to fit the nonlinear transformation function,and the mutual information of separation signals is used as the evaluation function.Then the parameters of polynomial and linear separation matrix can be estimated by mutual information of separation signals and particle swarm optimization algorithm,thus the source signals can be separated from the mixed signals.The two-phase flow signals with noise which are obtained from upstream and downstream sensors are respectively processed by nonlinear blind source separation method so that the noise can be effectively removed.Therefore,based on these noise-suppressed signals,the distinct curves of cross correlation function and the transit times are obtained,and then the velocities of two-phase flow can be accurately calculated.Finally,the simulation experimental results are given.The results have proved that this method can meet the measurement requirements of two-phase flow velocity.