大型汽轮发电机转子绕组匝间短路故障的诊断研究

通过对24 MW汽轮发电机内部转子绕组匝间运作时出现的短路故障的分析和讨论,并结合积累的运行经验,对其故障诊断技术所存在的问题及其特点进行深入性的探讨.据此提出了转子绕组匝间发生短路故障的几种常见形态,同时,在各种状态模式下,对所选用的检测方法的适用性进行了有效评价,为未来一段时间内进一步提高匝间短路故障的检测以及诊断水平提出了一些建议.     

匝间冲击试验在发电机磁极线圈绝缘缺陷检测中的运用

介绍了某水电站水轮发电机磁极线圈匝间绝缘试验方法,利用交流阻抗试验、匝间冲击试验等手段,检测线圈的匝间有无短路故障。通过不同试验手段对比,表明匝间冲击试验比常规试验更能准确检测出线圈匝间短路点及绝缘薄弱点。     

基于FEPG的电动机匝间短路温度场分析

基于电动机匝间短路故障与定子电阻、电流、槽内导体损耗之间的定量关系。提出了电动机匝间短路温度分析有限元计算模型,研究了匝间短路位置和故障程度与电机温升之间的关系．并运用有限元分析软件FEPG对电动机空载、满载及匝间短路故障后的温度场进行了仿真计算．证明该模型是正确的。     

发电机振动故障原因分析及解决方法

介绍了三钢集团公司2#汽轮发电机组振动故障情况,经过全面检测、分析、排查,诊断为发电机转子匝间短路引起的振动。发电机解体检查发现转子绕组匝间短路严重,通过发电机转子大修等检修手段消除发电机组振动故障,保证了2#发电机组安全运行。     

基于虚拟仪器技术的异步电机定子匝间短路故障在线监测系统

为实现对异步电机定子匝间短路故障进行在线监测,提出了一种基于虚拟仪器技术的故障监测系统设计方法.以高性能ARM微处理器S3C2410X作为电机物理量采集的核心,利用LabVIEW7.0虚拟仪器开发平台计算电机定子负序电流,并考虑电机绕组先天不平衡因素,定义了故障灵敏度因子反映匝间短路故障程度.实验结果表明:该系统有较好的可靠性和实时性,并具备较强的匝间短路故障辨识能力,方法可行.     

晶闸管整流弧焊机故障检修一例

我厂购买的一台ZX5-500型弧焊机,在工作一个月后,出现了焊接电弧燃烧不稳定的故障,影响了生产任务的完成。 经查焊机使用说明书与此故障现象相应的原因有:(1)线路中某处接触不良。(2)滤波电抗器匝间短路。(3)分流器到控制箱的两根引线断开。对照上述原因进行检测,均没有发现问题。     

电气设备故障检测技术讲座 第二讲 电机故障检测技术（下）

三、电机绕组故障检测 电机绕组的故障主要有以下四种：匝间、相间短路,三相阻抗失配,断路,绝缘损坏。这些故障往往始于电机内部绕组品质的变化。由于长期运行或过载,特别是频繁地起动及反向,过电流产生的热量使绕线绝缘层发生质变,造成初期局部的匝间短路或对地短路,短路严重时,将导致电机烧损。 匝间短路与对地短路是电机最常见的故障。这两种故障虽然机理相同,但相互独立：有时候出现匝间短路的电机,其对地绝缘是好的;而有些电机对地绝缘性能下降,甚至绝缘阻值只有几千欧,但匝间是完好的。有些情况下,这两种故障也会相互影…     

大型汽轮发电机转子绕组短路故障的检测技术研究

针对大型汽轮发电机转子绕组短路故障的检测与保护,存在很多问题有待解决。本文首先就转子绕组匝间短路和接地短路的故障特点与其相关继电保护存在的问题进行了深入分析,接下来介绍了目前应用比较成功的两种典型现代故障检测技术,基于静态检测的RSO脉冲法与基于动态检测的气隙探测线圈法。随后重点就基于气隙探测线圈法所采集的暂态微弱故障信号的数学模型,研究了小波变换的多分辨分解技术在其提取故障特征环节中的应用,分析了其有效性和可行性。本文最后进行了相关的总结和展望。     

采用像素编码技术的感应电机定子故障诊断

分析了三相定子电流Park矢量轨迹与电机故障特征之间的内在联系,确定可以将Park矢量轨迹像素作为定子线圈故障诊断的依据.在此基础上,从模式识别的角度,提出了一种基于Park矢量轨迹的极坐标系"像素"编码的定子线圈匝问短路故障诊断方法.该方法采用像素矩阵编码提取匝间短路故障特征矢量,运用RBF神经网络实现对故障的自动识别.试验结果表明,该方法诊断定子线圈短路故障,具有较高的准确性.     

水泵电机匝间短路的分析

分析水泵电机匝间短路的书写模型,通过实例分析匝间短路的物理现象,从而说明加强电机匝间短路检测的重要性。     

GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

Rotor vibration characteristics are first analyzed,which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault,air-gap dynamic eccentricity fault,or imbalance fault,and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs.Next,the characteristics of the stator winding parallel branches circulating current are analyzed,which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs,and the fundamental circulating current will increase when the air-gap eccentricity fault occurs,neither being strongly affected by the imbalance fault.Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults,a method of generator vibration fault diagnosis,based on rotor vibration and circulating current characteristics,is developed.Finally,the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.     

Detection of stator winding faults in induction motors using three-phase current monitoring

The objective of this paper is to propose a new method for the detection of inter-turn short circuits in the stator windings of induction motors. In the previous reported methods, the supply voltage unbalance was the major difficulty, and this was solved mostly based on the sequence component impedance or current which are difficult to implement. Some other methods essentially are included in the offline methods. The proposed method is based on the motor current signature analysis and utilizes three phase current spectra to overcome the mentioned problem. Simulation results indicate that under healthy conditions, the rotor slot harmonics have the same magnitude in three phase currents, while under even 1 turn (0.3%) short circuit condition they differ from each other. Although the magnitude of these harmonics depends on the level of unbalanced voltage, they have the same magnitude in three phases in these conditions. Experiments performed under various load, fault, and supply voltage conditions validate the simulation results and demonstrate the effectiveness of the proposed technique. It is shown that the detection of resistive slight short circuits, without sensitivity to supply voltage unbalance is possible.     

转子绕组短路故障下不平衡电磁力计算方法

通过建立发电机有限元分析模型,得到故障下发电机内部磁力线走势、发电机气隙磁通密度的变化以及短路位置、短路匝数和励磁电流对转子不平衡电磁力的影响。对工程实际中常用的等效磁通法和磁势叠加法进行了分析比较,同时改进了现有的等效磁通计算方法。将两种方法不平衡电磁力的计算结果与有限元方法结果进行比较,指出了结果存在差异的原因。     

An accurate technique of measurement of a transducer output by using a modified two core saturable reactor

Saturable reactor or transductor used as a magnetic modulator or amplifier for the measurement of the small value DC output signal of a transducer may suffer from error due to the fact that a part of the current drawn from the transducer by the transductor unit is utilized to magnetize the core material. In this paper a modified two core saturable reactor circuit has been proposed to eliminate this error. This unit also minimizes some other errors like common mode error, material error, etc. Theory of operation and design of the circuit has been explained in this paper. The circuit has been tested by using a millivolt input signal as well as a thermocouple to measure temperature. The experimental results are presented in this paper. Linear static characteristic graphs have been observed.     

新能源汽车油泵电机电磁力建模及其匝间故障监测方法研究

新能源汽车油泵电机出现匝间故障,无法保证燃料供给、控制压力、提供润滑和冷却等,威胁行车安全。对此,本文提出了一种基于电流和振动信号相结合的匝间故障在线监测方法。首先,根据麦克斯韦张量法构建含有故障电流谐波的电磁力模型。其次,设计了一个多传感器的电机信号采集电路。最后,采用改进的自适应经验模态分解法对经降噪后的振动信号进行自适应分解,利用相关系数法对所得的一系列本征模式函数筛选和重构。综合评估峭度与均方根值之比以及包络谱特征因子,得到故障特征指标提升52.3%,表明重构信号具备更高的敏感性,并通过电流波形分析验证了重构信号与故障特征的一致性。该研究对油泵电机故障诊断和状态预测具有重要工程意义。     

锂离子电池外部短路电压行为预测模型评价

锂离子电池外部短路瞬间产生大电流引发安全事故频繁发生,精确的模型是风险预警的基础。围绕外部短路故障,从不同初始荷电状态(State of charge,SOC)、不同温度两方面开展了Thevenin等效电路模型与单粒子电化学模型的电压预测精度评价与复杂性对比。结果表明,Thevenin模型精度随初始SOC降低而下降,随环境温度升高上升;单粒子模型精度受初始SOC影响较小,随温度升高先上升后下降。针对Thevenin模型短路中精度下降等问题,提出了应用电感元件的模型优化方法。模型方均根误差小于60 mV,精度提升了76%;针对单粒子模型在外部短路大电流中精度变差的问题,提出了使用双电层放电和锂离子扩散限制进行建模的模型优化方法。模型方均根误差小于40 mV,精度提升了64%。优化后的模型分析结果表明：Thevenin模型实时性高,单粒子模型弥补了电池漏液时Thevenin模型的失效,但计算复杂;前者可用在外部短路的前期诊断和预警中,后者可用在外部短路发生后的热管理或热安全研究中。     

Simulative and experimental investigation on stator winding turn and unbalanced supply voltage fault diagnosis in induction motors using Artificial Neural Networks

The three-phase shift between line current and phase voltage of induction motors can be used as an efficient fault indicator to detect and locate inter-turn stator short-circuit (ITSC) fault. However, unbalanced supply voltage is one of the contributing factors that inevitably affect stator currents and therefore the three-phase shift. Thus, it is necessary to propose a method that is able to identify whether the unbalance of three currents is caused by ITSC or supply voltage fault. This paper presents a feedforward multilayer-perceptron Neural Network (NN) trained by back propagation, based on monitoring negative sequence voltage and the three-phase shift. The data which are required for training and test NN are generated using simulated model of stator. The experimental results are presented to verify the superior accuracy of the proposed method.     

大型汽轮发电机端部电磁场数值分析

为解决大型汽轮发电机在不同运行条件下端部绕组的动力响应问题,基于全变量法,首先建立了汽轮发电机动态性能计算机仿真的等效电路模型和计算方法,以及端部涡流场、电磁力数值分析的三维有限元模型和计算方法;然后应用前述的模型和计算方法,采用有限元分析软件ANSYS,对某台大型汽轮发电机不同运行工况下的端部动态涡流场、电动力进行了数值分析和计算.研究结果表明,该方法在大型汽轮发电机绕组工程设计方面具有一定的指导意义.     

Automatic optical inspection for detecting defects on printed circuit board inner layers

This paper studies automatic optical inspection for detecting defects on the printed circuit board inner layer. The development of this study can be divided into five stages, they are reference image rebuilding, inspection image normalization, image subtraction, defects separation and defect classification. In the image subtraction stage, the difference between the reference image from the printed circuit board design and the inspected image is checked for defects. Each defect region is separated using a defect outer boundary tracing method. A boundary state transition method is proposed to classify the defect types. This system can recognize eight defect types, open, mouse bite, pinhole, missing conductor, short, spur, excess copper and missing hole. In addition, a comparison with the methods described in the literature is made, proving that the proposed method produces better results .