Real-Time Implementation of Wavelet Packet Transform-Based Diagnosis and Protection of Three-Phase Induction Motors

This paper presents a real-time implementation of an online protection technique for induction motor fault detection and diagnosis. The protection system utilizes a wavelet packet transform (WPT)-based algorithm for detecting and diagnosing various disturbances occurring in three-phase induction motors. The criterion for the detection is the comparison of the coefficients of the WPT of line currents using a mother wavelet at the second level of resolution with a threshold determined experimentally during the healthy condition of the motor. The algorithm is implemented in real-time using the Texas Instrument TMS320C31 32-b floating-point digital signal processor with the help of object-oriented programming. The proposed technique is tested on two three-phase induction motors. The online test results give a response signal at the instant or within one cycle of disturbance in all cases of investigated faults. In addition, the algorithm is also tested during no load and full load operating conditions of the motor.     

汽轮发电机组转子复合故障的研究

研究了一种综合应用神经网络的分类功能和D—S推理融合诊断的故障决策新方法。针对大型汽轮发电机组多重故障复合发生的实际情况，首先应用神经网络技术对复杂故障进行了初步诊断，然后应用D—S证据理论对诊断结果进行融合决策。解决了汽轮发电机组多重复合故障的诊断问题，并给出了诊断实例。     

A New Longitudinal End Effect Factor for Linear Induction Motors

The longitudinal end effect in a linear induction motor (LIM) is analysed assuming two travelling magnetic flux density waves in the airgap: the wave travelling with synchronous velocity and the wave representing end effect [1]. A simple equation for the end effect factor which modifies the airgap EMF is obtained, and a simple equivalent circuit incorporating the end effect factor is established. Analysis is compared with measurements from two largescale single-sided LIM's. The equation for the end effect factor is sufficiently accurate to be used for design studies of LIMs. Since end effects are negligible at low speeds, the end effect factor has application for medium and high-speed LIMs.     

Effect of Coils on Natural Frequencies of Stator Cores in Small Induction Motors

The electromagnetic noise of a motor is offensive to the ear. Most electromagnetic acoustic noises are generated when natural frequencies of a stator core coincide with or closely parallel frequencies of the magnetomotive forces. Therefore, to minimize such noise, an accurate estimate on natural frequencies of the stator is necessary. In this paper, the stator of a small induction motor is studied as to various factors such as the stator core shape, including a circumferential cut, and stiffness of varnished random winding in stator slots. Furthermore, the effect of coil ends on natural frequencies of the stator core is newly clarified. As a result, in the 2.2kW motor, an equivalent Young's modulus as stiffness of windings in the slots is obtained as being about 1/100th that of copper. Also, study clarifies that coupling vibration arises from the coil end and the stator core. It is found that this coupling vibration can be estimated briefly from a two free degree system.     

A Reconfigurable Motor for Experimental Emulation of Stator Winding Interturn and Broken Bar Faults in Polyphase Induction Machines

The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished.      

Characterization of Flux Rotation and of the Ensuing Core Losses in the Stator of Induction Motors

A literature survey reveals that the study of rotational power losses in stator cores has been conventionally performed by means of finite-element analysis. This paper proposes an alternative characterization of rotational power losses in the tooth roots - a region that has been long known as a seat of flux rotation - relating some geometric dimensions to the values of flux density of interest to compute the rotational losses over the region. A simplified computation of maximum and minimum flux densities is proposed based on the trajectories of flux at singular time intervals. This enables the calculation using analytical expressions. For that reason, the proposed approach improves the power losses analysis in early design stages, showing the impact of projected geometries on the total loss estimate. Moreover, it consequently provides a tool to include the rotational losses estimate within optimization-oriented iterative searches.     

Interturn Fault Diagnosis in Induction Motors Using the Pendulous Oscillation Phenomenon

A robust interturn fault diagnostic approach based on the concept of magnetic field pendulous oscillation, which occurs in induction motors under faulty conditions, is introduced in this paper. This approach enables one to distinguish and classify an unbalanced voltage power supply and machine manufacturing/construction imperfections from an interturn fault. The experimental results for the two case studies of a set of 5-hp and 2-hp induction motors verify the validity of the proposed approach. Moreover, it can be concluded from the experimental results that if the circulating current level in the shorted loop increases beyond the phase current level, an interturn fault can be easily detected using the proposed approach even in the presence of the existence of motor manufacturing imperfection effects     

Application of an Additional Excitation in Inverter-Fed Induction Motors for Air-Gap Eccentricity Diagnosis

In this paper, the application of an additional excitation in induction motor (IM) drives for static, dynamic, and mixed eccentricity diagnosis is proposed. The additional excitation consists in a predefined inverter-switching pattern that is applied on the motor for a short time, while the fundamental excitation is canceled. This excitation was used previously to implement a position estimation strategy. The strategy obtains information about the rotor position from the motor saliencies effects over the zero-sequence voltage. The air-gap eccentricity is a kind of saliency that affects the zero-sequence voltage and allows the use of the additional excitation for eccentricity diagnosis. For the evaluation of the feasibility of this proposal, a multiple-coupled circuit model of the IM is used. The effects of series and series-parallel stator winding connections on the diagnosis signals are shown. Experimental results to validate the proposal are also given. These results show that it is possible to use the diagnosis strategy in a self-commissioning scheme     

A New Rapid Nonlinear Simulation Method for Switched Reluctance Motors

This paper presents a new rapid nonlinear simulation method for switched reluctance motors (SRMs). An exact mathematical relationship among the magnetization curves of an SRM is obtained by curve fitting the variable parameters in the Torrey model. Only geometry-based requirements are taken as input needed. Since complete magnetic characteristics are not necessary, a lot of preliminary measurements and calculations are eliminated. The dynamic performances under two operating conditions are predicted using the proposed method, and the measured results are obtained by an experimental laboratory setup. Furthermore, predictions using other two traditional models are presented for the purpose of comparison. Experimental and simulation results verify the accuracy and rapidity of the proposed method.      

含分布式电源配电网故障的Petri网诊断方法

现有含DG配电网的Petri网故障诊断方法需要多次假定正方向,造成故障诊断过程复杂、计算量大。通过分析故障后功率方向和初始托肯赋值的特点,提出一种基于功率方向的初始托肯判据,并基于该判据只需要假定一次正方向和一次定位,就能定位出故障区段;同时对FTU遥信数据和遥测数据设置不同置信度,使得区段定位的容错能力得到了提高。通过配电网算例分析,验证了所提方法在含DG配电网故障诊断中的优势。     

柴油机故障的灰色优劣度诊断法

本在灰色理论基础上提出了诊断柴油机故障折灰色优劣关联度法，并用于６Ｅ３９０柴同的工况评价和故障诊断，收到了良好的效果。     

基于过程的旋转机械振动故障定量诊断方法

基于状态的故障诊断方法,由于缺少对振动过程规律的描述,因而存在一定的不足,以信息熵方法为基础,通过多通道多转速下的信息熵矩阵来描述振动过程的变化规律,从而提出一种基于过程的信息融合故障诊断的新方法.并通过实例计算以及对振动信号的分析,验证了该方法在故障诊断方面的准确性.     

Fault Detection and Diagnosis in an Induction Machine Drive: A Pattern Recognition Approach Based on Concordia Stator Mean Current Vector

The aim of this paper is to study the feasibility of fault detection and diagnosis in a three-phase inverter feeding an induction motor. The proposed approach is a sensor-based technique using the mains current measurement. A localization domain made with seven patterns is built with the stator Concordia mean current vector. One is dedicated to the healthy domain and the last six are to each inverter switch. A probabilistic approach for the definition of the boundaries increases the robustness of the method against the uncertainties due to measurements and to the PWM. In high-power equipment where it is crucial to detect and diagnose the inverter faulty switch, a simple algorithm compares the patterns and generates a Boolean indicating the faulty device. In low-power applications (less than 1 kW) where only fault detection is required, a radial basis function (RBF) evolving architecture neural network is used to build the healthy operation area. Simulated experimental results on 0.3- and 1.5-kW induction motor drives show the feasibility of the proposed approach.     

局域波法在转子系统多故障监测中的应用研究

局域波法是基于信号局部特征,通过该方法可得到信号的瞬时频率和构成能量－时间－频率三维分布的Hilbert时频谱。用局域波法分析了转子系统出现裂纹和磁摩故障耦合时的振动特征,结果表明局域波特别适合分析非线性非平稳信号,能清晰地描述振动信号的时频特征,为工程实际中转子系统的故障监测和诊断提供依据。     

基于随机矩阵理论的配网故障可观的PMU优化配置方法

定义故障在全网最不灵敏节点发生时可检测为随机矩阵理论下的全网可观。相同故障发生在不同节点时对配网影响程度不同,对应的随机矩阵理论指标MSR的跌落程度不同。提出了配网故障时全网可观的PMU优化配置方法。分别在所有节点设置单相和两相接地故障,得到2种情况下全网的电压数据并计算相应的MSR;对2种MSR进行加权,计算出各节点灵敏系数;以灵敏度最低的节点发生故障时全网可观为目标,按灵敏程度逐次减去不灵敏节点的PMU并计算相应的MSR,直到故障不可检测,得到的PMU配置即为最后配置。以IEEE36节点和IEEE39节点模型进行仿真,验证了在该PMU优化配置方案下,可用随机矩阵理论对配网进实时监测,在故障发生时能准确检测到故障并确定故障发生的时刻。     

混合SVM-HMM方法在旋转机械启动过程故障诊断中的应用研究

提出了旋转机械启动过程故障诊断的一种新框架一混合SVM—HMM方法。该方法把SVM的输出信息通过sigmoid函数和高斯模型转化为后验概率的形式,并把它引入到HMM模型隐状态的观测概率。根据模拟实验数据计算表明,该方法是十分有效的。     

Optimization of Three-Phase Induction Motor Design Part I: Formulation of the Optimization Technique

This two-part paper deals with the optimization of the induction motor designs with respect to cost and efficiency. Most studies on the design of an induction motor using optimization techniques are concerned with the minimization of the motor cost and describe the optimization technique that was employed, giving the results of a single (or several) optimal design(s). In the present paper, a more comprehensive study on the optimization of a three-phase induction motor design was performed. This includes the relationship between motor cost, efficiency, and power factor; the effect of the properties of the electrical steel; and other effects as they occur in an optimal design. In addition, the optimization procedure that was used in this paper includes a design program, where some of the secondary parameters (which are called here variable constants), are modified according to the optimal results, in contrast to other studies where these parameters remain constant for the entire optimization. In this part, a new mathematical formulation of the optimization problem of the induction motor is presented.