Effects of symmetrical voltage sags on squirrel-cage induction motors

This paper analyzes the symmetrical voltage sag consequences on the induction motor behavior when single- and double-cage models are considered, namely current and torque peaks, and speed loss. These effects depend on several variables like sag type, duration and depth. Voltage sag effects are studied by using single- and double-cage models for three motors of different rated power. The double-cage model always predicts torque and current peaks higher than those of the single-cage model. The single-cage model predicts that voltage sags can produce motor instability, whereas the double-cage model is always stable. Therefore, the double-cage model must be used for the simulation of the squirrel-cage induction motor, because the single-cage model can give erroneous results in some situations.     

Nonlinear systems time-varying parameter estimation: Application to induction motors

In this paper, an algorithm for time-varying parameter estimation for a large class of nonlinear systems is presented. The proof of the convergence of the estimates to their true values is achieved using Lyapunov theories and does not require that the classical persistent excitation condition be satisfied by the input signal. Since the induction motor (IM) is widely used in several industrial sectors, the algorithm developed is potentially useful for adjusting the controller parameters of variable speed drives. The method proposed is simple and easily implementable in real-time. The application of this approach to on-line estimation of the rotor resistance of IM shows a rapidly converging estimate in spite of measurement noise, discretization effects, parameter uncertainties (e.g. inaccuracies on motor inductance values) and modeling inaccuracies. The robustness analysis for this IM application also revealed that the proposed scheme is insensitive to the stator resistance variations within a wide range. The merits of the proposed algorithm in the case of on-line time-varying rotor resistance estimation are demonstrated via experimental results in various operating conditions of the induction motor. The experimental results obtained demonstrate that the application of the proposed algorithm to update on-line the parameters of an adaptive controller (e.g. IM and synchronous machines adaptive control) can improve the efficiency of the industrial process. The other interesting features of the proposed method include fault detection/estimation and adaptive control of IM and synchronous machines.     

On a mathematical model of squirrel-cage induction motors

Contents This paper presents a mathematical model of 3-phase squirrel-cage induction motor accounting for a very high number of space harmonics in which, due to application of a special transformation of voltages and currents, a differential equation system with constant coefficients is obtained. The number of space harmonics is so high that it is possible to perform a direct computation of the alternating component of the electromagnetic torque which decides on the parasitic synchronous torque.An application example of this model for the analysis of steady and dynamic states of a concrete squirrel-cage motor is given.

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Über ein mathematisches Modell des Käfigläufermotors

Übersicht Im Artikel wird ein mathematisches Modell dreiphasiger Käfigläufermotoren mit Berücksichtigung einer großen Zahl räumlicher Harmonischer vorgestellt. Unter Anwendung einer speziellen Transformation der elektrischen Spannungen und Ströme erhält man ein Gleichungssystem mit konstanten Koeffizienten Die Zahl der räumlichen Harmonischen ist so groß, daß die Berechnung der Wechselkomponenten des elektromagnetischen Moments und damit des parasitären synchronen Moments möglich ist. Die Anwendung des mathematischen Modells wird anhand eines Beispiels für dynamischen und statischen Betrieb vorgestellt.

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List of symbols and abbreviations N number of bars of the rotor cage - L ₈ total self inductance of stator phase winding - M ₈ mutual inductance of stator windings - R _rg,L _rg resistance and leakage inductance of a rotor end ring segment-respectively - R _b,L _b resistance and leakage inductance of a rotor cage bar-respectively - k=0,1, ... N—1 number of the rotor currents symmetric component and theM _sr matrix column corresponding to it - l equivalent axial length of stator core - equivalent width of air-gap - p pole pair numer - z number of turns per phase - v order of harmonic - k _sv stator winding coefficient for thev-th harmonic - k _rv rotor winding coefficient for thev-th harmonic - k _skv skewness coefficient for thev-th harmonic - U _s stator voltage vector in symmetrical components - U _r rotor voltage vector in symmetrical components - i _s stator current vector in symmetrical components - O zero matrix - R _s stator resistance matrix - R _r rotor resistance matrix - LL _s stator inductance matrix - L _rr rotor inductance matrix - M _sr matrix of stator-rotor mutual inductances - T _e electromagnetic torque - T _m motor load torque - rotor position angle - ₀ initial rotor position angle - rotor angular velocity - (*) conjugation index of a complex number - Re {y} real part of a complex number - Im {y} imaginary part of a complex number - T transposition index - [X] ^x highest integer not greater thanX and of the same sign asX - U r.m.s. value of the phase voltage - _u pulsation of supply voltage     

Parameter identification of deep-bar induction motors using genetic algorithm

In recent years, the use of three-phase deep-bar induction motors in power systems has increased. Proper modeling and precise parameter identification of the model are essential for motors’ operating analysis. In this paper, among the proposed models of deep-bar induction motors, a model based on two-axis theory is discussed and developed to improve precision. A real coded genetic algorithm estimates the parameters of the model. The accuracy and validity of the model and its identified parameters are verified with the help of a 5.5 kW, 380 V, 50 Hz, 1,450 rpm deep-bar induction motor.     

Modeling of saturation in induction machines using EMTP, PSpice and a dedicated computer program

The effects of saturation in an induction motor's performance during a direct on-line start are studied using three different techniques. In the first method, the motor is modeled using the well-known Electromagnet Transients Program (EMTP) with saturation included in the magnetizing branch only. Secondly, the motor is modeled using PSpice, a popular circuit simulation software package, where magnetic-core saturation is modeled more accurately than in EMTP. In the final method, the motor is modeled by taking into account cross- as well as magnetic-core saturation and implemented in a dedicated computer program. A comparative evaluation of the results is presented.     

Adaptive non-linear speed control of induction motors

In this paper we present two adaptive non-linear speed control algorithms for induction motors. They employ input-output linearization techniques for the motor model in the stator fixed reference frame. The first control algorithm directly tracks speed and rotor flux. The second is designed using torque and rotor flux tracking and is extended for speed control. A key point is that this algorithm ensures exact current limitation in the known parameter case. The adaptation based on Lyapunov design can cope with rotor and stator resistance variations. Significant simulations using sampled controllers are presented emphasizing adaptation and current limitation effects.     

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     

Load torque identification in induction motor using neural networks technique

Induction motors are widely used in several industrial sectors. However, the dimensioning of induction motors is often inaccurate because, in most cases, the load behavior in the shaft is completely unknown. The proposal of this paper is to use artificial neural networks as a tool for dimensioning induction motors rather than conventional methods, which use classical identification techniques and mechanical load modeling. Simulation results are also presented to validate the proposed approach.     

基于神经网络的异步电动机定,转子电阻在线估计法

矢量控制是一种对电机参数依赖性很强的控制方法,本文采用了神经网络辨识非线性系 统的思路,提出一种电机定、转子电阻参数的在线估计方法,用于电压控制型矢量解耦控制系统 中,可以基本消除电机参数变化对系统控制性能的影响,并通过仿真验证了该方法的可行性和有 效性。     

Steady-state torque control system with secondary-current feedback for three-phase squirrel-cage induction motors

This paper presents a highly stable steady-state torque control system with a feedback of a secondary current signal. The torque control system is constructed with a feedback of the secondary current (I₂) signal using a quick response magnetic-field sensor constructed with an amorphous core multivibrator bridge, which can solve the secondary resistance change problem for temperature variation in the IM. Moreover, we added a state feedback to the system to improve the response speed for the unit step function of a torque order. The I₂ sensor method has advantages especially at a low-speed range, in which conventional method using an integrator shows control errors.     

无轴承异步电机数学模型与解耦控制

针对无轴承异步电机是一个强耦合的非线性复杂系统,实现其电磁转矩和径向悬浮力之间的成功解耦是电机稳定悬浮工作的关键问题.在给出了无轴承异步电机径向悬浮力产生原理的基础上,推导了径向悬浮力和电机旋转部分的数学模型,并采用转子磁场定向控制策略设计了无轴承异步电机矢量控制系统,利用Matlab/Simulink工具箱对该控制系统进行了仿真.仿真试验表明,该控制系统不仅可以实现转子稳定悬浮,而且实现了径向悬浮力和旋转力矩之间的解耦控制,电机具有良好的动、静态性能.     

一种改进的电动机静态聚合方法

电动机参数是电力系统电压稳定、暂态稳定的关键因素之一.在基于统计综合法的负荷建模中,如何提高电动机参数的聚合精度是重要课题.针对传统电动机聚合方法没有考虑聚合前每台电动机稳态滑差的不足,提出了一种改进的电动机的静态聚合方法.该方法首先根据聚合前各电动机的惯性时间常数、暂态电抗、转子回路时间常数、临界滑差定义了一个电动机的特性指标,并按照该指标对电动机进行分组.然后将每组中的电动机根据其稳态等值电路转化为3种阻抗并联的形式,在对3种阻抗分别聚合后再还原为一台电动机稳态等值电路.算例表明该方法能够有效提高仿真精度.     

Influence of skin effect on mutual inductance of double-cage induction motors

The influence of skin effect on mutual inductance is important to determine fundamental and harmonic currents in the double-cage. A numerical example shows that significant errors arise from existing methods when losses, torque, or power are evaluated. Several methods to analyze mutual inductance are presented. In spite of skin effect, the relation, M_2,3=M_3,2, holds. For the analysis of a double-cage, a direct method not requiring mutual inductance is described.     

基于SIMULINK的异步电机的建模与仿真

利用MATLAB软件中的动态仿真工具SIMULINK ,建立了异步电机的仿真模型 ,并通过实验验证了所建电机模型的可行性和实用性。     

Leakage flux saturation effects on the transient performance of wound-rotor induction motors

The prediction of induction machine performance has traditionally been based on the constant parameter models. This approach was later replaced by considering saturation in the main flux paths. However, such models have not been sufficiently accurate for certain transient conditions such as on-line starting and short-circuit. So, an accurate study of their performance should necessarily consider the magnetic saturation effect both in the main and leakage flux paths. In this paper, an experimental procedure to determine the machine parameters and saturation characteristics is adopted. The adopted experimental procedure facilitates the measurement of both stator and rotor leakage reactance saturation characteristics. Two models of saturated induction motors are developed to predict the transient performance of a laboratory wound-rotor induction motor. The results calculated by the proposed models considering and ignoring the leakage flux saturation are compared with the experimental results. The model that considers saturation in the leakage flux paths produces more accurate transient responses.     

笼型感应电机流体流动对温度场分布的影响

以一台Y802-2型笼型感应电机为例,对中小型感应电机三维流体流动与传热进行了研究。根据样机的通风结构及传热特点,建立外部近似无限大流场空间与电机三维有限元结构模型,并在电机内外流场空间中建立了转子表面旋转流体薄层和风扇旋转流体区域。给定流场空间中运动区域与静止区域边界条件及基本假设,采用有限体积法对流体运动方程和能量方程进行耦合求解,可以得到流场中流体介质的运动状态以及电机内外各个表面的散热系数,并以此为依据对电机三维全域温度场进行数值计算。将流体场耦合计算得到的温度场分布和传统温度场计算结果分别与实验测量值进行了比较,证明了中小型感应电机三维流体场与温度场存在着强烈的耦合关系,基于流体流动的温度场计算结果较传统方法得到的温度分布更具准确性与合理性。     

一种感应电机转子电阻在线识别新方法

基于感应电机在静止A、B、C和转子速a、b、c两种坐标系下的数学模型,推导出一种转子电阻在线识别的新方法。在MATLAB/SIMULINK环境下建立了系统的仿真模型,实例仿真验证了方法的准确性。该方法简单,且避免了奇异解的问题。     

永磁同步电机绕组电感的饱和效应

系统地分析了永磁同步电机绕组自感和互感的饱和效应,指出饱和效应引起这些电感随转角变化的二次谐波和一次谐波分量。实验结果验证了分析的结论,研究的成果深化了永磁同步电机的理论,对建立精确的分析模型和正确的参数确定方法有重要的指导意义。     

异步电动机T型等值电路参数估算的新方法探讨

提出一种基于铭牌数据的三相异步电动机T型等值电路参数的新估算方法 ,有较强的实用价值。并为进一步研究更加准确的的异步电动机参数辨识方法打下良好基础     

Effect of the stator slot opening on the electromagnetic vibration in a squirrel-cage induction motor

Field harmonics produce a radial electromagnetic force in a squirrel-cage induction motor with a particular number of rotor slots corresponding to the number of poles. The radial force causes vibration and acoustic noise. In this paper, a simplified equation for the radial force at no-load is introduced, and the relation between the width of the stator slot opening and the radial force is discussed quantitatively. The field harmonic component produced by the interaction between the fundamental magnetomotive force due to the stator current and the pulsation of air-gap permeance dominates for the radial force. Furthermore, the vibration of the stator core due to the radial force is calculated under a simple assumption. The calculated results are verified by experiments.