Harmonics in the Squirrel Cage Induction Motor,Analytic Calculation Part Ⅱ:Synchronous Parasitic Torques,Radial Magnetic Forces

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

CALCULATION OF SATURABLE LEAKAGE REACTANCES OF SQUIRREL CAGE ASYNCHRONOUS MOTORS

A general method of calculating the saturable leakage reactances of squirrelcage asynchronous motors is presented.The method synthesized the variety of effectswhich affect the saturation of leakage magnetic circuit.And the saturable reactances canbe precisely evaluated in any running condition.The computation results of Y-series mo-tors are in good agreement with the test ones.

Intelligence Based Soft Starting Scheme for the Three Phase Squirrel Cage Induction Motor with Extinction Angle AC Voltage Controller

Whenever a squirrel cage induction motor is started, notable electromechanical torque and current pulsations occur. The adverse effects of starting torque pulsations and high inrush current in induction motor are eliminated using digital power electronic soft starting schemes that guarantee higher degrees of compliance of the requirements of an ideal soft starter for the induction motor. Soft starters are cheap, simple, reliable and occupy less volume. In this paper, an experimental setup of soft starting technique with extinction angle AC voltage controller and a speed and stator current based closed loop scheme is demonstrated using Artificial Neural Network (ANN) and Fuzzy Logic Control (FLC) by the way of MATLAB/SIMULINK based simulation. The ANN based soft starting scheme produces best results in terms of smooth starting torque and least inrush current. The results thus obtained were satisfactory and promising.

三相鼠笼异步电动机无传感器转速检测技术及其适应性

针对三相鼠笼异步电机无位置传感器快速傅立叶变换(fast Fourier transformation,FFT)测速方法需要预先知道转子槽数,且测试精度易受噪声干扰和采集时长等因素的影响,提出一种基于奇异值分解-Prony(singular value decomposition-Prony,SVD-Prony)算法的无位置传感器高精度转速测量技术。运用电机学相关理论,研究转子槽谐波测速机理,并给出整数倍率转子槽数的计算方法。在分析并明确定子电流噪声影响和FFT法存在检测精度受采样时长限制等问题的基础上,研究基于奇异值增长率的SVD滤波方法和用于辨识转子槽谐波的Prony算法,并以Y160M-4型电机为研究对象,在不同运行状态下对该技术的适应性进行分析。在此基础上,构建相关物理测试平台,对YE90S-2型电机进行实测。结果表明,在相同采集情况下,所提方法测试绝对误差仅为FFT测速方法的几分之一,检测精度大幅提高。

鼠笼转子端部扭振特性研究及其对结构可靠性影响

针对变频器驱动下牵引电机受到谐波转矩的影响,分析了谐波转矩对铜条式鼠笼转子结构的作用机理。采用试验与仿真相结合的方法识别鼠笼转子端部特性。首先,通过模态分析,获取了鼠笼转子的模态参数;然后,建立了基于模态试验的转子等效有限元模型,分析了其在12倍频特征电磁激励下的静强度及谐响应。最后,基于导条振动测试平台,研究了鼠笼转子端部扭振特性,并对载荷放大效应进行了验证,为提升铜条式鼠笼转子端部结构的可靠性提供了一定的理论支撑。

机车牵引电机转子模态试验及仿真优化研究

牵引电机转子作为电机旋转的核心,转子的固有频率应避开实际的工作频率、工作转速。基于软件的有限元分析法是目前在设计阶段应用最广泛的固有频率计算方法,而影响计算结果准确性包括材料参数、各部件间的实际接触状态等。通过LMS公司的采集系统进行实际模态测试,并采用Ansys的有限元分析法,考虑导条和端环、导条和铁心、铁心和转轴实际接触状态计算转子的固有频率。根据实际模态测试结果,以验证Ansys计算结果的实效性,为进一步提高牵引电机转子模态仿真精度提供有益参考,也为进一步改进转子结构,保证转子在实际运行中不会发生共振提供依据。

基于永磁辅助转子和改进磁障的笼型感应电机的研究

为了有效提高笼型感应电机的功率因数,通过对传统三相四极笼型感应电机的转子结构进行改造,提出了一种基于永磁辅助转子和改进磁障的新型笼型感应电机。采用二维瞬态有限元分析方法,对比和分析了所提新型感应电机和传统感应电机在磁路分布、磁通密度、功率因数和效率方面的性能差异。结果表明,相比于传统感应电机,所提出的新型感应电机可将功率因数提升至0.86~0.98,效率最高可达到95.5%,新型感应电机能够在优化的功率因数下更加高效地运行。

鼠笼异步电机多故障智能诊断基本研究

围绕鼠笼式异步电动机的结构、工作原理及其多故障智能诊断技术进行了深入研究。介绍了鼠笼电机的构造和基本工作原理,包括其定子和转子的主要组成部分,以及电机的起动和运行机制。分析了鼠笼电机可能出现的机械和电气性质故障,如转子断条和轴承故障,并推导了相应的故障特征频率分量,阐述了其在故障诊断中的作用。指出了鼠笼电机故障诊断的难点和现有技术的局限性,并提出了基于参数测定和机器学习技术的智能诊断方法。强调了智能故障诊断技术在保障工业生产连续性和安全性方面的重要性,并展望了未来的研究方向和技术发展。

异步电动机的转子断条问题研究

讨论了异步电动机转子断条故障的特征机理,介绍了通过定子电流监测进行故障诊断的方法。概述了鼠笼式异步电动机转子断条故障可能由机械应力、过载电流和设计缺陷等因素引起,并强调了这种故障对电机性能的负面影响,包括转速异常、噪声增大和潜在的安全风险。提出了通过监测气隙磁场变化和定子电流频谱分析来诊断故障的方法。在正常情况下,电机磁动势平衡对称,而转子断条破坏了这种对称性,导致转矩波动和平均转矩下降。通过对定子电流进行频谱分析,检测到特定的谐波分量。提出结论,尽管传统理论侧重于基波的影响,实际上其他定子电流成分也参与了谐波的生成,并且可以通过监测特定频率的谐波分量来判断转子是否存在断条故障。

New Approach to the Power Selection for Asynchronous Motor

The heating calculation of three-phase squirrel- cage asynchronous motor on the condition of starting for a prescribed rotary angle is firstly studied with time dissection method and its corresponding algorithm is provided. Then based upon the algorithm, a new method for motor power selection is established. Motor initial power determined by load power ischecked and modified in terms of time crit erion, heating criterion,and starting torque criterion.An appropriate motor power which meets three criterions is obtained at last, in the meantime, working displacement matrix andfrequency matrix used for control are acquired. Lifting motor of MDJ1800 low-level high- speed palletizer is taken as a reaI case in the paper.

三相鼠笼异步电机转子断条故障检测

针对转子断条故障信号易被基波淹没,故障特征不易提取及容易误判等问题,提出在空载低压运行状态下通过基于奇异值增长率的SVD-Prony算法检测转子断条故障。在研究转子断条故障特征及转子槽谐波测速机理的基础上,给出了整数倍转子槽数的理论计算公式及转子断条故障信号频率与转子槽谐波频率的关系表达式,并通过转子槽谐波频率验证转子断条故障信号的正确性,以此提高转子断条故障检测的有效性。通过仿真,验证了所提方法的有效性和实用性,对电机转子断条故障检测研究具有重要意义。

Time-stepping finite element analysis on the influence of skewed rotors and different skew angles on the losses of squirrel cage asynchronous motors

To study the influence of skewed rotors and different skew angles on the losses of squirrel cage asynchronous motors,a 5.5-kW motor was taken as an example and the multi-sliced field-circuit coupled time stepping finite element method(T-S FEM)was used to analyze the axially non-uniform fundamental and harmonic field distribution characteristics at typical locations in the stator and rotor cores.The major conclusions are:firstly the skewed rotor exhibits a decrease in the harmonic copper losses caused by slot harmonic currents in the stator winding and rotor bars.Secondly,the skewed rotor shifts the non-uniform distribution of field in the axial direction,which leads to more severe saturation and an increase in iron losses.The heavier the load,the more pronounced the increase in iron losses.Furthermore,the influences of different skew angles on motor losses are studied systematically,with skew angles from 0.5 to 1.5 stator tooth pitch.It is found that the lowest total loss occurs at 0.8 stator tooth pitch,and the slot harmonics can be decreased effectively.

鼠笼转子端环应力研究及护环选取原则

鼠笼式异步电动机,铜条放置在转子槽中,两端通过端环短接。电机运行时,端环承受高速旋转带来的离心力以及热胀带来的热应力,端环受到的合应力可能会超出材料许用值,此时是否加护环成为了电动机可靠运行的必要考虑因素。本文通过对比三种不同的解析方法,推导出一种简单、可靠的解析计算方法以及判断标准,并通过与有限元分析法对比及试验验证得出用线速度界定护环的方法是可行的。本文完成对鼠笼型电动机转子护环受力的分析,并为实际项目中转子护环的选取提供切实可行的方法与理论依据。

梯形小波变换及其在鼠笼电动机转子故障分析中的应用

提出了梯形小波函数和小波变换。梯形小波函数具有良好的时域和频域局部化特点和强的选频能力。梯形小波变换适用于电力系统故障分析 ,尤其适用于电动机鼠笼断条以及发电机转子故障分析 ,因而具有较大的社会经济效益。

感应电动机定转子全域温度场数值计算及相关因素敏感性分析

提出了针对无轴向通风冷却电机温度场计算的新思想,合理处理了电机定子与气隙之间以及转子与气隙之间复杂的对流散热过程,妥善解决了定、转子之间的热交换问题。给出了散下线定子绕组的等效热模型,简化了计算难度并且节省了计算时间。在此基础上建立了笼型感应电动机定、转子全域温度场二维数学模型和二维有限元计算模型。计算了电机额定负载运行时定、转子的稳态温度场以及气隙温降;实验结果验证了该电机温度场计算模型的合理性和计算结果的正确性。在该温度场计算模型的基础上,分析了电机温度场对定子铜耗、散热翅高度以及定子绕组浸渍质量等相关因素的敏感性,为电机优化设计奠定理论基础。

免疫原理用于异步电动机故障诊断的研究

基于免疫系统的基本原理,提出了一种用于异步电动机故障诊断的新方法。根据免疫系统中T细胞和B细胞的机能,分别建立了T模块和B模块。T模块用来区分电动机的正常状态和故障状态,B模块用来改进T模块在故障诊断空间的覆盖。T模块具有自适应功能,可以根据探测得到的信息调整其状态位置,便于将来更好地进行故障诊断。B模块采用变异和克隆机制,具有学习、记忆等功能,有利于诊断知识的扩充。通过测量异步电动机定子电流频谱,采用T、B模块成功地诊断出电动机的转子断条故障,证明了该方法的正确性和有效性。

基于瞬时功率信号频谱分析的鼠笼式异步电动机转子故障在线诊断方法

该文介绍了一种基于瞬时功率频谱分析的鼠笼式异步电动机转子故障监测与诊断方法。采集定子某两个端子之间的线电压和对应的线电流,由二者的乘积即可构成瞬时功率信号。理论分析表明,与常见的基于定子线电流频谱分析方法相比,使用瞬时功率信号能避免基波电流对故障特征成分的影响,更好地突出故障特征,分离复合故障。这些都有益于对故障程度的量化,和诊断规则的建立。通过对样机进行断条和偏心故障设置,多种故障情况下的实验结果也证实了上述结论。

基于Hilbert模量频谱分析的异步电动机转子故障在线监测与诊断方法

Hilbert 变换是数字信号处理中的一种理想的移相方法。对某一信号进行这种变换,可得到其共轭信号。该文将Hilbert模量定义为原始信号与其共轭信号的平方和,并在此基础上提出了一种基于定子电流Hilbert模量频谱分析的异步电动机转子故障在线监测与诊断方法。理论分析和实验结果表明该方法可以有效地诊断鼠笼式异步电动机的转子故障。与需要同时采样三相电流的扩展的Park捠噶糠椒ㄏ啾?该方法大大节省了硬件和软件开销。

基于最小二乘支持向量机的电机故障鉴别

针对异步电机的构造与转子故障特征,基于统计学习理论提出了信号处理技术与支持向量机故障诊断相结合的方法,以鼠笼式异步电动机为研究对象,建立了电机转子故障实验系统,并采集了电机故障信号,使用最小二乘支持向量机(LS-SVM)进行故障分类。其次针对鼠笼式电机转子多故障分类问题,提出了小波包分析两种不同故障信号预处理方法,将采集的电机机壳振动信号分别进行分析,提取了故障特征向量,并结合LS-SVM分类功能,实现对电机转子不同故障的有效分类。实验结果表明,小波分析与LS-SVM结合的方法具有很好的分类精度。