六相感应电机新颖控制策略下的转子电压研究

由于多相电机控制模式相对复杂,该文提出一种新颖的控制方式:即在六相感应电机定子侧通入梯形波相电流,使得其中三相为励磁绕组,另外三相为转矩绕组,从而实现励磁磁链和转矩磁链解耦模拟直流电机控制模式而省去复杂的派克变换。本文主要对磁势解耦时转子磁链和转子感应电压、电流进行了理论和有限元分析和计算,并实验测量了梯形波相电流驱动下六相感应电机转子感应电压、电流,结果表明有限元分析和实验结果是一致的。     

小型五相感应电机设计及槽数选取分析

针对某小型五相感应电机基于磁路法开展初步设计,利用Ansoft软件对电机槽型进行了优化设计,并介绍了通过绕组函数法计算其电感参数的方法;针对小型五相感应电机中定转子槽数进行了筛选,针对定子20槽、30槽、40槽、转子26槽的电机分别进行了仿真分析,验证了设计的合理性,从起动转速、定子电流、径向气隙磁密的仿真对比分析,得出定子40槽可以作为转子26槽的小型五相电机优选的结论。     

基于梯形波相电流控制的六相感应电机性能分析

六相感应电机通过使用梯形波相电流而把定子绕组分成励磁绕组和转矩绕组,这样可以实现励磁磁场和电磁转矩直接控制而不需要复杂的派克变换,本文主要对磁势解耦时磁链和转子感应电压进行了理论和有限元分析,并实验测量了梯形波相电流驱动下六相感应电机转子感应电压,结果表明转子感应电压的有限元分析和实验结果是一致的。     

H桥型五相感应电机SVPWM控制技术

多相感应电机较传统三相电机具有诸多的优势,但多相电机电压空间矢量多,控制复杂。针对该问题,建立了五相感应电机的数学模型,分析了H桥逆变器的结构与工作原理。对五相电机的电压空间矢量进行了分析与计算,综合考虑电压脉动与开关损耗等因素,给出了五相电机的电压空间矢量脉宽调制SVPWM（space vectors pulse width modulation）算法。该算法在MATLAB的仿真平台和基于双数字信号处理器DSP（digital signal processor）控制的变频调速系统上均予以实现,证明了方法的有效性。     

基于SVPWM五相感应电机直接转矩控制研究

针对感应电机直接转矩控制(DTC)采用开关表的滞环方法时,存在电流和转矩脉动等问题,提出在DTC中应用空间矢量脉宽调制(SVPWM)的方法。根据五相感应电机模型和DTC基本原理,推导出参考电压矢量。分析了五相逆变器的空间电压矢量,并从中选取出22个有效电压矢量,根据最近四矢量SVPWM算法,计算出第k扇区中工作电压矢量的作用时间。建立了基于双DSP控制的实验系统,实验结果表明,该方法减小了电流和转矩脉动,具有良好的稳态和动态性能。     

五相感应电机直接转矩控制研究

在对五相感应电机直接转矩控制中空间电压矢量进行详细分析的基础上,给出了一套系统调速整体控制方案。在该控制系统中,磁链和转矩均是闭环控制,其值在一个微小的滞环内波动,稳态情况下,其指令值与实际值可认为相等。此时,定子电流空间矢量幅值是一定值,该值变化可认为是由定子电阻变化引起的,由此给出了一套简单、易于实施的定子电阻在线辨识算法。仿真结果表明,提出的控制方案在理论上和实际上是可行的。     

基于转子磁链优化的五相感应电机电子变极策略

针对五相感应电机（FIM）指数响应转矩跟踪电子变极运行不平稳问题,分析得出转子磁链饱和是导致该问题的主要原因之一,计及磁链饱和提出一种转子磁链优化（RFO）电子变极控制策略。分析了FIM电子变极过程中两个控制平面转子磁链叠加是导致磁链饱和的原因,设计了转子磁链控制函数,并采用磁链幅值和电磁转矩约束函数使转子磁链逼近临界值,优化了转子磁链控制。基于FIM的Speedgoat半实物实验平台,对所提RFO方法进行了实验验证,对采用和未采用RFO的指数响应转矩跟踪电子变极控制策略进行对比实验研究。实验结果表明,所提策略使转速波动减小了50%,转矩波动减小了67%,有效改善了电子变极过程中电机运行平稳性。     

船用五相感应电机模型预测电流控制研究

传统五相感应电机矢量控制中包含多个PI参数需整定,且存在电压调制环节而造成控制系统结构复杂。引入模型预测电流控制代替矢量控制以解决该问题。获得预测模型后,在预测电流控制器中对五相逆变器输出的32个电压矢量进行遍历寻优,得到最优电压矢量的开关状态。为解决五相感应电机谐波空间电流影响,在代价函数中使用权重因子对谐波电流项进行调节,实现对谐波电流的抑制,并给出谐波含量与转速及权重因子之间关系。仿真结果表明,应用模型预测电流控制策略的五相感应电机动态响应速度快,在工况切换时依然具有良好的控制效果。     

基于电感参数补偿的五相感应电机容错控制

为抑制五相感应电机定子开路故障下的转矩脉动,本文提出一种基于不对称电机模型的电感参数补偿策略。从空间矢量解耦的角度,推导了定子绕组不同开路情形的坐标变换矩阵,建立了五相感应电机故障后的数学模型。通过修正故障后电机的电感参数和解耦矩阵的系数,实现了故障情况下五相感应电机的转子磁场定向控制,保证其在故障后平稳运行。以a相绕组开路故障为例,仿真和实验结果表明该策略能够有效地抑制转矩脉动,改善电机故障下运行的性能,此外这种分析方法可以推广到任意的多相电机。     

Cause and analysis of stator and rotor failures in three-phasesquirrel-cage induction motors

The squirrel cage induction motor has limitations, which, if exceeded, will result in premature failure of the stator or rotor. The authors identify the various causes of stator and rotor failures. A specific methodology is proposed to facilitate an accurate analysis of these failures. Failures of the bearings and lubrication systems are excluded     

Analysis of rotor failures in squirrel-cage induction motors

The authors describe a procedure for analyzing rotor failures in squirrel-cage induction motors. They attempt to identify the various kinds of failure classes and patterns and relate them back to the probable cause of failure. They discuss five key areas that must be considered and related to one another in order to accurately diagnose the cause of rotor failure: failure class, failure pattern, appearance, application, and maintenance history. Finally, a summary of typical failures and tell-tale rotor appearances is presented     

Modeling of induction machines including stator and rotor slot effects

Three-phase as well as single-phase induction machines form the backbone of a substantial portion of the adjustable-speed drives' applications. Among the current estimation techniques available for speed-sensorless induction motor drives, speed measurement based on rotor or principal slot harmonics (RSH or PSH) detection in machine line current happens to be a prominent one. In practice, two predominant RSH can be seen. The present paper attempts to investigate the effect of slot permeance on the production of RSH. Simulation studies on a small motor but with a popular stator, rotor slot, and pole combination suggest that their effect is less significant compared to rotor space harmonics effect. Also, out of the two aforementioned RSH, the cause of the less significant slot harmonic is shown to be the negative-sequence-current-induced reverse rotating field. Voltage unbalances and constructional imperfections can cause negative-sequence current even in a healthy machine. Thus, although the less significant RSH is absent in the simulated line current of an idealized machine running from a balanced supply, it can be detected in an actual machine.     

Characteristic analysis of an induction motor with an unequal slot pitch cage rotor

Recent developments in induction motors have been moving forward reducing the size and weight of motors. At the same time, there are demands for much quieter operating conditions. Various design methods have been applied to reduce the vibration and acoustic noise of induction motors. One method is to make the slot pitches of the cage rotor unequal, to avoid the resonance with the natural frequencies of the stator frame. In this paper, our purpose is to create guidelines for reducing noise. As the first step for this purpose, we developed a method to analyze the voltage and torque equations of an induction motor with an unequal slot pitch cage rotor and discussed the characteristics from the analyzed currents. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 44–52, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10032     

Transient and steady-state operation of induction motors with rotor asymmetries

Contents Steady-state analysis of induction motors with asymmetrical rotor impedances is presented by the application of the symmetrical-components method. New and general equivalent circuits are derived, and the analogy is pointed out between the equivalent circuits of this type of rotor asymmetries and other types. It is shown how the equivalent circuits can be extended for the case of transient operation when the rotor speed is constant.General state-variable equations are given for the calculation of transients. These can be easily solved by a digital computer using well known techniques.

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Übersicht Das stationäre Verhalten von Asynchronmaschinen mit Unsymmetrien im Rotorkreis wird mit Hilfe symmetrischer Komponenten behandelt. Neue und allgemeine Ersatzstromkreise werden abgeleitet und die Analogie zwischen den Ersatzbildern für diese Art von Rotorasymmetrie und anderen Arten aufgezeigt.Ferner wird gezeigt, wie die Ersatzschaltbilder für den nichtstationären Betrieb bei konstanter Drehzahl erweitert werden können. Für die Berechnung des nichtstationären Verhaltens werden allgemeine Zustandsgleichungen angegeben, die mit bekannten Verfahren einfach auf Digitalrechnern gelöst werden können.

     

Characteristics of three-phase induction motors under unbalanced rotor impedances

An analysis is developed for three-phase induction motors with balanced or unbalanced rotor impedances. The validity of this analysis is verified by comparing its results, under balanced conditions and in the steady state, with those obtained using conventional methods. The method is also verified experimentally for a 7.3 kW, 220 V, four-pole, 50-cycle slip-ring induction motor with balanced or unbalanced rotor impedances. The analysis is then used to study the characteristics of three-phase induction motors under unbalanced rotor impedances.