Magnetic suspension force in an induction bearingless motor with a squirrel cage rotor

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearing‐less motor, both 4‐pole and 2‐pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three‐phase windings, thus a 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and a simulation model of suspension force is then constructed. It is shown that the response and the phase of suspension force are delayed in the case of cage rotors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 77–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20340     

基于绕组函数的鼠笼式异步电动机故障仿真

仿真是故障研究的一种重要途径,仿真效果与模型系数的计算准确度密切相关。异步电动机仿真模型中有大量的电感参数．利用绕组函数计算这些电感参数适用范围广、精度高。在此基础上．建立了鼠笼式异步电动机正常时和定子匝间短路、转子断条、气隙偏心等常见故障情况下的数学模型．并进行仿真分析。仿真结果与理论分析得到的结论基本吻合,表明模型及参数计算正确,可为故障诊断提供依据。     

基于绕组函数的鼠笼式异步电动机电感参数解析计算

从绕组函数出发,推导了鼠笼式异步电动机的电感参数计算公式,这些公式既适合于正常状态,也适合于各种故障状态,尤其是动态和静态偏心,且精确度高,为仿真研究打下了坚实的基础。根据样机参数进行了仿真计算,正常电动机的仿真结果与已往的经典方法结果完全吻合,静态偏心状态下的结果与预期的一致,验证了该方法的正确性。     

Causes and characteristics of the electromagnetic vibration of a capacitor motor under load

Capacitor motors (CRMs) are widely used to drive industrial equipment and home electric appliances. Recently, reduction of the vibration and noise of CRMs has become increasingly important from the standpoint of environmental improvement. However, electromagnetic vibration of CRMs under load has not been sufficiently analyzed. The present paper theoretically and experimentally discusses the causes and characteristics of CRM electromagnetic vibration under load. The primary conclusions are as follows:

• (1) The general formula for the dominant electromagnetic vibration caused by electromagnetic force waves was derived, including the influences not only of a backward magnetic field but also of magnetic saturation.
• (2) The dominant electromagnetic vibration of CRMs is theoretically attributed to three types of electromagnetic force waves. Two types of electromagnetic force wave are generated by the interaction of two forward magnetic fluxes, such as those of a three‐phase squirrel‐cage induction motor, and the other type of electromagnetic force wave is generated under the influence of a backward magnetic flux.
• (3) The characteristics of the dominant electromagnetic vibration depending on the load and the running capacitance are subdivided theoretically and experimentally into three types based on the characteristics of the electromagnetic force wave and the equivalent circuit current.
• (4) The influences of magnetic saturation in dominant electromagnetic vibration have been verified experimentally and their causes have been clarified theoretically in relation to electromagnetic force waves. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(4): 68–76, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20129

     

鼠笼式异步电动机转子故障检测方法

基于定子电流的频谱分析方法是异步电动机状态监测与故障诊断的主要途径。总结了异步电动机转子断条和偏心故障时，定子电流中可能出现的故障特征频率成分，通过对同时存在断条和偏心故障的异步电动机的实验结果分析，发现基波周围的断条和偏心特征频率成分尽管容易出现频率重叠，但因其幅值较大，对其进行监测仍是故障诊断最有效的途径；避免误诊的方法是对断条和偏心特征频率成分各自的分布规律进行监测分析，如果同时结合槽谐波及其周围的偏心特征频率成分的监测，将会使结果更准确。     

Magnetic field analysis of a squirrel cage induction motor considering rotor skew and higher harmonics in the secondary current

This paper describes a method to analyze harmonic magnetic fields of squirrel cage induction motors considering rotor skew and higher harmonics in the secondary current. The proposed method is based on a two‐dimensional finite element method. The rotor skew structure is expressed by multiple 2D finite element mesh models, produced in suitable axial positions, and the magnetic field in each mesh model is calculated by the revised secondary current taking into account the skew effect. The secondary currents, magnetic flux densities, and electromotive forces are calculated by the proposed method. Then the differences between a skewed rotor and a nonskewed rotor are discussed. From the comparison between the calculated and the experimental results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic components of induction motors. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 98–109, 1999     

变频电源笼型异步电机断条故障诊断仿真

为了探讨笼型异步电动机转子导条断裂故障诊断的有效方法,根据多回路电机模型参数及正弦脉宽调制(SPWM)原理,建立了变频电源供电笼型异步电机在正常情况和转子断条故障情况下的运行状态仿真模型,并在MATLAB仿真环境比较电机定子单相电流频谱及三相平均瞬时功率频谱。通过分析检验了仿真系统模型的可行性和实用性,证实了平均瞬时功率频谱比电机定子电流频谱具有更佳的断条故障特征分辨力和故障判断准确性,尤其是在变频供电情况下优势极为突出,从而确立了合适的断条故障判据。     

负载振动与气隙偏心下电机电流调制机理分析

分别分析了感应电机负载转矩振动和气隙偏心对定子电流的调制机理,同时针对转矩振动频率与电机转子转频一致时,两者对定子电流调制结果在频域上难以区分开的特点,利用Wigner时频域分析方法,计算了负载转矩振动和气隙偏心时电流边频分量的相位差,指出二者时频分布特征的区别,为有效、准确地进行电机气隙偏心故障诊断提供理论依据。     

鼠笼式异步电动机转子故障在线监测与诊断方法

提出了以平均瞬时功率为监测量进行鼠笼式异步电动机转子复合故障的监测与诊断方法。该方法不需要已知电动机的定／转子参数,可以实现复合故障的准确分离。理论分析和实验结果验证了该方法的有效性。     

双定子笼型感应电动机的数学模型及性能计算

对双定子笼型感应电动机建立了数学模型,进行了性能分析与计算,利用Ｃ＋＋语言编制了计算机辅助设计程序,并设计与试制了两台２２ｋＷ、６极的模型机,通过实验证明了理论分析与计算的正确性。     

鼠笼异步电机起动性能的时步有限元计算

时步有限元方法是计算鼠笼异步电机暂态起动特性的一种有效方法，本文针对当前该方法在工程应用中存在的问题展开了研究。在转子转动的处理方面，通过对现有方法进行改进，得到了一种新的处理有限元运动问题的方法——边界耦合法，解决了现有方法存在的效率低、通用性不强和时闻步长不确定等问题。本文还讨论了转子电路方程的建立和电磁转矩计算等方面的问题。     

A study of the electromagnetic vibration of a capacitor induction motor caused by time-harmonic voltages

In recent years, power source voltage waveform distortion has become noticeable, as electrical appliances with rectifier circuits have become widely used. Connecting capacitor inductor motor (CRM) to such distorted supply, or controlling CRM by simple controller with a switching device (such as triacs), harmonic voltage is supplied to CRM. In that case, CRM produces electromagnetic vibrations caused by not only the fundamental voltage but also time-harmonic voltages in the distorted voltage. In addition, CRM produces electromagnetic vibration due to backward magnetic fields. Thus, it is difficult to clarify a relationship between electromagnetic vibration of CRM and harmonic voltages. In this paper, the causes of the electromagnetic vibration of CRM operating under distorted wave supply voltage are discussed. First, a general equation of dominant electromagnetic force waves is shown considering not only forward magnetic fields but also backward magnetic fields. Using a general equation, causes of dominant electromagnetic vibration can be clarified. Next, by discussing in detail some examples of the dominant vibration, the relationship between the vibration and harmonic voltages becomes evident. Furthermore, the relationship between the vibration and backward magnetic field is clarified.     

计及频率特性的感应电动机参数变化对负荷特性的影响

对于网架结构比较薄弱的省网系统或者系统解列后形成的孤岛,发生故障时会引起比较大的频率波动。感应电动机作为电力系统动态负荷的主要成分,进行建模时考虑其频率特性尤为重要。基于感应电动机数学模型,考虑恒机械转矩、恒机械功率和变机械转矩等不同负载特性,在计及频率特性的情况下,通过解析法得到感应电动机转子滑差、有功功率和无功功率的表达式。当感应电动机的定子电感、转子电感、励磁电感和转子电阻变化幅度分别为±30%时,分析负荷特性参数变化对不同频率下的感应电动机吸收有功功率和无功功率的影响。利用Matlab建立感应电动机五阶电磁暂态仿真模型,仿真分析感应电动机参数变化对负荷特性的影响。将理论计算与仿真实验的结果进行对比,验证了所提方法的正确性。     

笼型转子断条感应电动机的易解数学模型

针对断条破坏了电机原有对称关系而使建模仿真变得困难,采用综合矢量法,建立了转子断条感应电动机易于求解的数学模型.对电机暂态及稳态仿真揭示了定子电流幅值与转矩随时间脉动的故障特征,得出了转子导条电流分布规律,表明与断条相邻及相距一对极距的导条电流最大.引人关注的是在转子端环间出现端电压,其值反映了转子电路不对称程度;揭示了故障特征随电机负载变化规律.定子电流实测与仿真结果相吻合证实了结论正确,有助于感应电机在线故障诊断.     

考虑频率特性的感应电动机负荷模型的对比研究

以往主要研究负荷的电压特性,很少研究频率特性。而在小电网或者薄弱电网频率可能有明显变化,所以需要研究电力负荷的频率特性。给出考虑频率特性的五阶电动机负荷模型和新三阶实用电动机负荷模型,提出两种负荷模型的参数辨识方法,通过蚁群算法辨识其中的重点参数。结合仿真算例,分别对比考虑和不考虑频率变化时的五阶电动机负荷模型、新三阶实用电动机负荷模型,还对比了两种负荷模型。根据新疆电网的实际扰动数据,对考虑频率特性的必要性进行了校验,结果表明,考虑频率特性所得参数辨识结果更精确、拟合效果更好,考虑频率特性时五阶电动机负荷模型效果更好。     

基于笼型电动机转子断条故障的诊断分析

为了解决目前已有的故障诊断方法只能诊断出电机是否发生转子断条故障而不能诊断出转子断条数目的问题,对电机转子断条故障进行了仿真和断条数目诊断方法的研究。首先对Y2-132M-4型的鼠笼式三相异步电机进行了建模,利用建立的模型对发生不同断条数的电机故障进行了仿真研究。然后,提出了基于机器学习的对转子断条故障的断条数目进行诊断的算法。实验结果表明,所提出的故障诊断分类方法实现了电机不同数目的转子断条故障的智能诊断分类,且诊断分类准确率达100%。     

磁悬浮轴承感应电机转子拍振机理及其抑制方法

针对高精确度磁悬浮轴承感应电动机转子运行中激发的拍振问题,研究拍振产生的机理及其抑制方法.分析磁悬浮轴承转子拍振的合成原理,通过理论分析和实验找出合成磁悬浮轴承转子拍振的两个分振动,即与转子转速同频的振动和与内嵌感应电动机旋转磁场同频的振动.结合磁悬浮轴承的特殊电气和机械结构对两个分振动特别是与旋转磁场同频振动的产生根源进行研究分析,并通过数值方法进行验证.根据研究结果提出抑制磁悬浮轴承转子拍振的可行措施.实验结果证明了拍振机理及抑制方法的正确性,实现了转子拍振的有效控制.     

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     

Magnetostriction and motor vibration

A quiet induction motor is strongly demanded today. Electromagnetic factors are a main cause of vibration and acoustic noise in a small induction motor. Electromagnetic forces and magnetostrictive forces are considered as the origin of electromagnetic vibration and noise. In this paper, magnetostrictive vibration of a ring of electrical steel sheets was simulated by the mechanical finite element method. Magnetostriction was assumed as external forces and they were added at each node of the meshed ring. Resonant frequency and the mode of the ring were calculated. In the steel sheet ring excited by a PWM voltage source inverter, the frequency spectrum of vibration of ring was measured and compared with the calculated results. It was confirmed that these procedures simulated magnetostriction behavior of electrical steel sheets. Furthermore, the electromagnetic forces of a small induction motor were calculated and compared with the magnetostriction data. It became clear that electromagnetic vibration was affected by the magnetostriction of steel. These results will be useful in the reduction of acoustic noise and the development of quiet motors. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 8–13, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10338