Forces acting on induction machine stator core due to winding faults

A newly developed model for direct calculation of the Fourier components of currents is presented. Any connection of stator coils including shortings, can be analysed. A formula giving forces acting on the stator has the form of a sum of various waves. The waves causing elliptical deformations of the stator yoke have been specially investigated. The calculation and measurement results given refer to a 7.5 kW machine.Ein neu entwickeltes Modell zur direkten Berechnung der Fourierkomponenten der Ströme wird vorgestellt. Beliebige Verknüpfungen der Ständerwindungen, darunter auch Kurzschlüsse, können analysiert werden. Der Ausdruck für die Kräfte hat die Form einer Summe von verschiedenen Wellen. Eingehender wurden jene Wellen untersucht, die zu elliptischen Verformungen des Ständers führen. Die Berechnungs- und Meßergebnisse betreffen eine 7,5 kW Maschine.     

PWM-VSI inverter-assisted stand-alone dual stator winding induction generator

This paper presents a novel usage of a dual stator winding three-phase induction machine as a stand-alone generator with both controlled output load voltage magnitude and frequency. This generator, with both three-phase power and control windings housed in the stator structure, has the load connected to the power winding and a three-phase pulsewidth modulation (PWM) voltage-source inverter sourcing the control winding. The input to the PWM inverter is either a battery source or a charged DC capacitor. The operational characteristics of these generator schemes with either of the two inverter sources are investigated and shown to have desirable performance. How the load voltage magnitude depends on the various control and design parameters such as rotor speed, compensating capacitance, and load impedance is determined using a detailed mathematical model of the system.     

Transient model for induction machines with stator winding turnfaults

A transient model for an induction machine with stator winding turn faults is derived using reference frame transformation theory. A state-space representation of the dynamic equations, suitable for digital simulation is provided. Steady-state equivalent circuits are derived, from which the sequence components of the line currents can be estimated as a function of fault severity. Experimental results are provided to validate the derived model     

A mathematical model of a single-phase induction motor with an asymmetric stator winding

A model of an induction motor with an asymmetric stator winding is developed; it may be represented as two phases connected in parallel or in series and displaced is space by some angle.     

带有电流控制电压型逆变器的新型双绕组异步发电机的电压控制

带有电流控制电压型逆变器的新型双绕组异步发电机不仅克服了传统异步发电机电压随负载变化的缺点,而且提高了系统的电磁兼容性。其控制系统由两个PI电压控制器和一个滞环电流控制器组成。为了对其电压控制性能和调节速度进行研究,本文建立了计及磁路饱和的双绕组异步发电机及其控制系统的数学模型。对负载、转速突然变化等动态过程中电压控制性能进行了仿真研究。结果表明,该系统具有较好的电压控制性能和响应速度。     

异步电动机定子绕组三维温度分布的测试与分析

为提高电动机运行温度保护的性能,本文针对全封闭外置风扇冷却电动机定子结构特点,设计了异步电动机温度测试方案,测量了定子绕组三维温度分布。测量结果表明,由于结构的不对称以及由此导致的散热条件不对称,电动机定子绕组的温度分布也是不对称的,最高温度区域位于接线盒区域的绕组端部。在电动机温度分布测试结果的基础上,分析了定子绕组温度分布特点及其原因,提出了电动机保护和优化设计的新思路,为实现电动机运行温度保护奠定基础。     

定子绕组匝间短路对无刷双馈电机电磁特性的影响

针对无刷双馈发电机定子绕组匝间短路的暂态电磁特性,采用多回路模型和有限元模型相结合的方法,建立了用于分析定子绕组短路故障的无刷双馈发电机场路耦合模型,充分考虑齿槽效应,铁磁材料饱和以及涡流效应等因素的影响.对发电机匝间故障前后暂态和稳态下的电磁转矩特征进行了频谱分析,在此基础上研究了不同频率电磁转矩分量随故障匝数及故障...     

交流电机变频调速系统人机界面通信

人机界面是用户和机器联系的中介。文中所设计的人机界面主要应用于中型交流电机变频调速系统，在采用I2C总线（Inter IC Bus)通信协议的前提下，建立了一套以带有液晶显示LCD（Liquid Crystal Dispay)模块和键盘的单片机为“主”，以数字信号处理器DSP（Digital Signal Processor)为“从”的界面通信系统，实验证明，该 系统有较好的实时性和正确的数据传输，能实现对电机运行状态的监测、控制及故障排除，是一种较为可行的方案。     

双馈异步风力发电机定子匝间短路故障诊断

提出利用零序电压对双馈异步风力发电机定子匝间短路故障进行诊断的方法。在对定子绕组匝间短路故障零序电压分量产生机理进行分析的基础上,提出以零序电压作为故障特征量进行故障诊断。建立双馈异步风力发电机仿真模型,通过改变模型中短路匝数和短路电阻实现了匝间短路故障模拟。对发电机在转速恒定条件下的不同状态发生定子绕组匝间短路故障进行了仿真研究。结果表明:定子发生匝间短路故障后,会在定子中产生零序电压,并随着故障严重程度的增加而增大;零序电压会受到电源不对称和负载情况的影响,且随着负载的增大有微弱减小,利用零序电压进行故障诊断时,需要补偿这些非电机故障因素的影响。     

Voltage distribution in the stator winding of an induction motor following a voltage surge

Contents  This paper presents results of voltage transient tests. The primary aim of these tests is to develop an experimental understanding of what happens after a voltage transient arrives at the stator winding of an electrical machine. The test was performed on the stator of a 6 kV induction motor. The present measurements are performed with a 42 V input voltage step transient. The results show that, among the stator coils, the highest voltage peak appears across the coil next to the input; thus, this first terminal-end coil is subjected to the highest voltage stress. It was found, additionally, that the surge voltage distribution within the first coil is independent of the terminating condition at the neutral end of the winding, i.e. either grounded or ungrounded. The direct measurement shows that the inter-turn voltage is non-linearly distributed and the amplitude of the inter-turn voltage of the first coil depends quite considerably on the features (e.g. length) of the cable feeding the winding. The present experimental findings should be of help to those concerned with the turn insulation in motors fed by a frequency converter and surge protection problems of large AC motors.

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übersicht  In diesem Artikel werden die Ergebnisse eines Testes pr?sentiert, welcher sich auf transiente Spannung bezieht. Das Hauptziel dieser Tests besteht in der Schaffung eines experimentellen Verst?ndnisses darüber, was passiert, wenn eine transiente Spannung an der Statorwindung einer elektrischen Maschine auftritt. Der Test wurde an einem Stator eines inodernen 6 kV Induktionsmotors ausgeführt. Bei den aktuellen Messungen betrug der Eingangswert der transienten Spannung 42 V. Diese war stufenf?rmig ausgebildet. Die Resultate zeigen, da? die h?chste Spannungsspitze in jener Statorspule auftritt, welche am n?chsten zum Spannungseingang angeordnet ist; daher ist diese Spule des Terminalendes der h?chsten Spannungsbelastung ausgesetzt. Weiter wurde herausgefunden, da? die Sto?spannungsverteilung in der ersten Spule unabh?ngig davon ist, welche Endbedingung am neutralen Ende der Wicklung vorliegt, d.h.ob Erdung vor liegt oder nicht. Die unmittelbare Messung zeigt, da? die Spannung zwischen den jeweiligen Windungen nichtlinear verteilt ist und die Spannung zwischen den jeweiligen Windungen der ersten Spule relativ stark davon abh?ngt, welche Eigenschaften der Draht der Wicklung aufweist (z.B. L?nge). Die erzielten experimentellen Erkenntnisse sollten all jenen von Hilfe sein, welche mit der Windungisolierung von Motoren mit Frequenzkonvertern und Problemen des Spannungsschutzes von gro?en AC-Motoren befa?t sind.

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Received: 6 December 1999     

基于空间矢量法的感应电机定子线圈故障检测方法研究

提出了一种基于空间矢量法的异步电机定子线圈短路故障检测方法，导出了与线圈短路故障相关的故障特征，定义了表征故障程度的灵敏因子λ。实验结果证实，该方法可准确检测出反映异步电机在定子线圈短路故障时的故障特征，其应用于异步电机定子线圈故障检测，准确可靠，方法切实可行。     

An online stator winding resistance estimation technique for temperature monitoring of line-connected induction machines

A new technique for stator-resistance (R/sub s/)-based thermal monitoring of small line-connected induction machines is proposed in this paper. A simple device is developed for injecting a small DC signal into line-connected induction machines for estimation of R/sub s/. The proposed DC injection device is capable of intermittently injecting a controllable DC bias into the motor with very low power dissipation. Experimental results under motor startup, load variation, and abnormal cooling conditions verify that the proposed technique provides an accurate estimate of R/sub s/ that is capable of responding to the changes in the motor thermal characteristics, resulting in reliable thermal protection. The proposed technique is a very practical method for thermal protection of small line-connected induction machines that can be implemented with low cost in a motor condition monitoring system.     

Speed- and current-sensorless field-oriented induction motor drive operating at low stator frequencies

This paper aims to demonstrate that, exploiting the sensorless zero-sequence (SZS) air-gap flux estimation technique, it is possible to realize field-oriented induction motor drives without speed and current sensors, able to operate down to zero speed. According to the SZS technique a zero-sequence stator voltage component is generated as a result of the injection of a suitable high-frequency signal on the stator voltage. By manipulation of such a zero-voltage component, that is unaffected by speed and load changes, it is possible to detect both the amplitude and the angular position of the air-gap flux. In the present paper, it is shown that such a technique allows for the estimation of the motor speed and the phase currents, enabling implementation of a field-oriented control as well as speed and current closed control loops using a simple hardware which, with minor modifications, resembles that of an inexpensive constant Volt/Hertz drive. Experimental tests are shown in order to practically confirm the expected features of the proposed approach.     

A frequency-domain detection of stator winding faults in induction machines using an external flux sensor

The aim of this paper is to present the advantage of stator fault detection using an external stray flux sensor in a working induction machine. In the past 20 years, stray flux sensors have been used for diagnostic purposes but rarely in the presence of a complex power supply such as a voltage static inverter. In this paper, it is proved that a simple external stray flux sensor is more efficient than the classical stator current signature analysis to detect inter-turn short circuit in three-phase induction machines. The new result is that, even in the presence of power supply harmonics, it is possible to easily detect the stator winding faults in the low-frequency range of the flux spectrum with low-frequency resolution.     

选择性发电机定子单相接地保护方法

在深入分析发电机对地泄漏电流(即3倍中性点侧零序电流与机端出线侧零序电流之差)的基础上,提出了一种通过比较发电机定子单相接地故障时各发电机泄漏电流的大小或方向进行保护的发电机定子接地保护新方法。该方法利用发电机对地泄漏电流的基波分量和3次谐波故障分量,分别判断单相接地点是否在本发电机定子绕组内部,实现100%定子接地保护。EMTP仿真分析表明该保护方法能有效检测定子单相接地故障和准确判断接地故障发电机,适用于各种中性点接地方式,具有鲁棒性强、准确度高等特点。     

模块组合式交流电机定子分块规则与不等跨距绕组研究

低速大功率交流电机是指转速低于500r/min、功率在兆瓦级以上的电机,主要应用在大型水轮发电机、永磁同步风力发电机以及大型矿井提升直驱和大型船舶主推进等场合,在国民经济中占有重要的位置。针对其传统制造过程中存在的加工、装配和维护困难等问题,提出了一种新型模块组合式定子结构。在研究定子分块规则的基础上,通过计算每极每相槽数q不同时定子独立模块所需最小槽数,以及对应情况下的绕组分布系数、短距系数和削弱谐波次数,从绕组利用率和削弱谐波能力方面总结出了对于该种电机而言每极每相槽数q的选取方法。最后搭建试验台,对样机进行了实验,实验结果表明了分块规律的正确性以及模块组合式定子结构的可行性,为进一步研究奠定了基础。     

感应电机定子温度场的数值计算

针对中小型感应电机结构复杂热模型难以建立的问题,以一台小型感应电机为例,采用有限元方法,建立了电机的二维温度场数值计算模型。给出了定子二维温度场计算的泛函以及相关热性能参数的计算方法;计算了不同负载运行时样机定子的稳态温度场。计算结果与实测值的比较,验证了所采用计算模型及方法的合理性。该电机温度场计算模型可以应用到其他同类电机定子温度场的计算与分析。在该温度场计算模型的基础上,分析比较了机壳散热翅高度的变化对电机定子温度场的影响,研究了气隙温度对定子温度场的影响。     

Neural network-based stator voltage compensator for low-frequency operation of a vector-controlled induction motor drive

The stator field-oriented sensorless vector control method is receiving wide attention from the standpoints of being sensorless and less dependent on the motor parameters. However, this method has a problem at low speeds because actual stator voltage does not coincide with the corresponding reference voltage owing to the quantization error in the controller, the discrete-time process, the forward voltage drop of switching devices, and the dead time of the inverter. In this study, an artificial neural network-based voltage compensator is proposed to reduce the voltage error between the reference and the actual voltages. The proposed method was performed on an experimental system and the results were found to be excellent.     

Problems with modern air-cooled generator stator winding insulation

Modern stator winding design and manufacturing methods have been successful in reducing the costs of turbine generators. Problems such as thermal cycling, coil abrasion in the slot and PDs in the endwinding have lead to failures after as little as five years of operation. To avoid premature failures, users of modern air-cooled machines should ensure they have a good purchase specification, are present at the factory for critical phases of machine manufacture, operate the machine within specification, keep the windings clean, and closely inspect the stator winding after about one year of operation. The latter is much more important than it was for hydrogen-cooled machines. Although some problems cannot be corrected, effective means are available to slow down the deterioration process, if the problems are discovered at an early enough stage     

多相电机定子绕组改进绕组函数的有限元分析

提出改进绕组函数的有限元算法,解决了改进绕组函数的准确计算问题。根据有限元算法和叠加原理,分析了线圈和多相电机相绕组的改进绕组函数的基本特征,并根据该基本特征研究了多相电机气隙磁动势分布和气隙电感。结果表明,多相电机相绕组的改进绕组函数与绕组函数之间的差别为与多相电机结构有关的函数,电机正常运行时,该函数通常只含偶次谐波,并会影响电机气隙磁动势分布的计算,进而影响交、直轴电感曲线的谐波,但对交、直轴电感曲线的直流分量影响较小,基本可以忽略。