Large induction motor anti-friction bearing selection

The majority of motor specifications utilize L₁₀ life as the sole selection criterion for anti-friction bearings. At times, L ₁₀ lives in excess of 100,000 hours are specified in an attempt to prevent recurring field problems when the failures are originating from nonL₁₀ mechanisms. In some cases, these failures occur indirectly from overspecifying L₁₀ life. Some general examples of this occurence are described. A successful bearing design requires the consideration of many equally important factors, which are discussed in this article     

Power factor and efficiency characteristics of an induction motor with free rotating magnets

We have developed a unique induction motor that has free rotating magnets inside its rotor. In experimental results for a prototype motor, we have obtained superior performance over existing motors in terms of the power factor, efficiency, and output torque. The experimental details are as follows. The power factor of the test motor is significantly improved in comparison with that of a conventional induction motor. The power factor can be held to be unity, leading or lagging by changing the line frequency and/or source voltage. This is a quite unique feature, because the power factor of the usual induction motors always lags. The improvement of the power factor is effective not only in decreasing current loss, but also in decreasing voltage drop in the line and increasing installation capacity. The efficiency of the motor is remarkably higher than that of similar-sized conventional induction motors over a wide output power range. Actually, in ordinary induction motors, the efficiency is reduced as the power and/or the source voltage are decreased. However, the proposed motor is driven at high efficiency by lower source voltages in lower power ranges. The efficiency is improved by reducing the secondary current and the magnetizing current. © 1998 Scripta Technica, Electr Eng Jpn, 125(3): 59–66, 1998     

Comparison of induction motor field efficiency evaluation methods

Unlike testing motor efficiency in a laboratory, certain methods given in IEEE Standard 112 cannot be used for motor efficiency evaluations in the field. For example, it is difficult to load a motor in the field with a dynamometer when the motor is already coupled to driven equipment. The motor efficiency field evaluation faces a different environment from that for which IEEE Standard 112 is chiefly written. A field evaluation method consists of one or several basic methods. This paper separates and compares the basic methods according to their physical natures. Their intrusivenesses and accuracies are also discussed. This paper is useful for field engineers to select or to establish a proper efficiency evaluation method by understanding the theories and error sources of the methods. The basic methods discussed are: nameplate method; slip method; current method; statistical method; equivalent circuit method; segregated loss method; airgap torque method; and shaft torque method     

基于红外测温的异步电机轴承故障诊断

针对远航舰船异步电机轴承经常烧毁的问题,以一台Y100L -2型电机为研究对象,采用有限元法建立电机转子三维导热模型,对电机轴承在不同的运行状态下的电机转子三维温度场进行仿真,并结合电机轴承故障的试验进行了分析.分析结果显示,不论轴承是否有故障,电机端盖温度均是沿径向从内到外逐步下降;在端盖轴承座正对部位,温度变化缓慢,但是从轴承外径继续向外,端盖温度下降迅速;负荷变化对电机端盖温升的影响远远大于轴承损坏对端盖温升的影响;不能仅仅凭借端盖表面温升来对相应轴承状态进行判断,可以通过同一种负荷条件下端盖表面温升的变化对轴承状态进行判断.     

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.     

基于转差率的感应电机最优效率控制

针对感应电机的能量优化问题,提出了一种基于转差率的感应电机最优效率控制方法和算法,用于恒压频比(VVVF)感应电机驱动系统,并给出仿真结果。该方法具有明显的节能效果。     

An evaluation of the electrostatic shielded induction motor: asolution for rotor shaft voltage buildup and bearing current

This paper evaluates a new induction motor, the electrostatic shielded induction motor (ESIM). An ESIM reduces rotor shaft voltages to levels below the bearing lubricant's electric field intensity breakdown level and offers one solution to accelerated bearing wear caused by fluting induced by pulsewidth modulated (PWM) inverters. The paper begins by reviewing shaft voltages and the resulting bearing currents when operated on PWM voltage source inverters. An example of bearing fluting is shown, and system models are presented and discussed. The construction details and test results for several ESIMs are presented. Experimental results show the ESIM solves the electrostatically induced rotor shaft voltage and bearing problem without degrading the electromagnetic performance of the motor     

On the influence of coil design and electromagnetic configurationon the efficiency of an induction melting furnace

An investigation is done on a novel configuration for an induction melting furnace which is a combination of conventional channel and coreless induction furnaces. The efficiency of the furnace is determined for various coil and magnetic core designs, and these designs are compared with one another. A finite-element simulation of the furnace is done and compared with the results from the experimental furnace in order to evaluate the value of these simulations in the development of furnaces. The method used in determining the efficiency is evaluated and suggestions on the improvement thereof is given     

基于MUSIC算法的感应电机轴承故障检测方法研究

分析了感应电机轴承发生故障时振动信号的特性以及MUSIC算法及其高分辨率谱估计的特点，提出了一种基于MUSIC算法的感应电动机轴承故障检测方法。结果表明，在短数据情况下，相对FFT分析技术，该方法频率分辨率更高，故障检测更为准确，且计算量小，有利于电机故障实时状态监测。实验证实，将该方法应用于感应电机轴承故障检测，可准确检测出轴承故障时在包络信号中的故障特征成分，方法切实可行。     

Vector theory of an induction motor

Basic concepts for the vector theory of an induction motor are proposed. The vector method is used to derive new systems of equations and limits for torques, phase angles and absolute values of currents, and the flux linkage for nonlinear saturation. The theory, which is confirmed by the experiment, may be used for the system optimization of induction motors and asynchronous electric drives based on the energy performance criteria.     

基于小波变换的改进LMS算法在异步电动机轴承故障诊断中应用

基于电机定子电流信号分析方法的异步电动机轴承故障检测中,计及实际电动机供电电压谐波和三相电压不平衡等外部因素的情况下,如何实现轴承故障的可靠检测一直是电动机故障检测领域的难题.对传统的定子电流频谱分析方法进行了深入研究,讨论了传统最小均方算法(LMS)自适应滤渡方法在信号处理中的不足.在此基础上,提出了将小渡分析、连续细化傅里叶变换和改进LMS自适应滤波方法有机结合的异步电动机轴承故障检测新方法.该方法能够正确判断轴承故障特征频率分量,从而提高异步电动机轴承故障诊断效果,实现轴承故障的可靠检测.实验结果表明了该方法的有效性.     

Fast efficiency optimization techniques for the indirect vector-controlled induction motor drives

This paper presents two simple and very useful techniques for the efficiency optimization of the indirect vector-controlled induction motor drives. In the synchronously rotating reference frame the flux-producing current is controlled until the power at the DC link is minimum. Of the two techniques, the first method controls the flux-producing current in a regular and smooth manner. The second technique combines loss model and search approaches in a unique way to propose a hybrid method, where the first estimate is from the loss model approach and the subsequent adjustment of the flux is through the search technique. Both the algorithms are simple, easily realizable, and offer fast convergence. Also, smooth control of the flux offers excellent dynamic performance. A comparative assessment shows that the hybrid method is the best, even if an approximate equivalent circuit for the induction motor is used for the analysis and optimization of the losses. The close agreement between the simulation and the experimental results confirms the validity and usefulness of the proposed techniques.     

Direct-drive induction motors: using an induction motor as an alternative to a motor with reducer

This article presents the performance and size comparisons of direct-drive induction motors with gearbox-driven systems. Three different low-speed applications with output speeds to the driven equipment ranging from 300-600 r/min is reviewed. In addition, permanent-magnet (PM) motor advantages and disadvantages are also discussed.     

最小磁场存储能量条件下的感应电机定子磁通幅值效率优化

本文借鉴互联和阻尼分配的基于无源性控制器设计的基本思想和设计方法,依据最小磁场能量原则,设计了一种新的转矩跟踪效率优化控制器。由于只针对分解后得到的电气子系统进行最小磁场能量优化和转矩跟踪控制器设计,得到的定子磁通幅值优化律不受转子电阻的影响,因此具有更强的参数鲁棒性。且控制器不需要观测转子侧的系统状态变量,控制律是全局定义的,不存在发散奇点,能够跟踪快速变化的转矩和磁通给定,从而保证了系统的动静态性能。仿真实验结果证实该控制器在保证系统具有良好的动静态性能的同时,能有效地提高感应电机轻载时功率因数,并取得良好的节能效果。     

Sensor-less speed control of an induction motor

Vector control systems of induction motors without speed sensors have been earnestly developed to obtain a simple construction. To estimate the rotor speed, these systems require information of machine parameters such as secondary resistance. Therefore their performance is sensitive to variations of secondary winding temperature. The authors propose two useful calculation methods for a speed sensorless system. The first is a rotor speed calculation method by which the exact speed can be computed directly. The method does not require information of the secondary resistance, which makes it free from variations of secondary resistance. The second is a direct secondary resistance calculation method. It can be applied to compensation in speed sensorless vector control for exact speed estimation of secondary resistance. The effectiveness of the proposed methods are verified by digital simulation and experimental results. In this article, the influence of the machine and control circuit parameters are also examined     

Analysis of an induction bearing by the finite element method

Contents This paper deals with an induction bearing with a symmetrical and an asymmetrical exciting current density distributions, supplied with a–c and d–c. Calculations of forces acting upon the shaft, power losses in the shaft and of torques braking it have been performed. The obtained results are shown in graphs.

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Analyse eines Induktionslagers mit der Methode finiten Elemente

Übersicht Im Beitrag wird das von dem Gleich- und Wechselstrom gespeiste Induktionslager mit einem symmetrischen und einem unsymmetrischen Strombelag betrachtet. Es werden Berechnungen der auf die Welle wirkenden Kräfte, der Verluste in der Welle und der auf die Welle wirkenden Bremsmomente, durchgeführt. Die Berechnungsergebnisse werden anhand von Diagrammen veranschaulicht.

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List of symbols vector potential (complex rms value) - A _i , A _j , A _k vector potential values in nodal pointsi, j, k (complex rms values) - A/n derivative of vector potential in the direction external to the region's boundary - A ^e functionA in the element ^e - B magnetic induction (complex rms value) - B _x , B _y components of the magnetic induction - F _x , F _y components of the force vectorF - conductivity of the shaft - h _x , h _y eccentricity of the shaft in the OX- and the OY-direction - J current density (complex rms value) - J _w exciting current linear density (complex rms value) - angle between theY-axis and the tracing radius of the boundary point - L length of the shaft - n rotational velocity of the shaft - magnetic permeability of the shaft - current pulsation - P power losses in the shaft - v _x , v _y components of the shaft's velocity in the OX-and the OY-direction     

基于模糊逻辑的自寻优感应电机能量优化控制

为了反映出不同负载和不同转速下各种电机运行状态对能量优化寻优过程的影响,提出了一种基于模糊逻辑的自寻优感应电机能量优化控制算法,引入了电压改变系数和最大调整电压,计算出最终的电压调整量,并给出仿真结果。该方法用于恒压频比(VVVF)感应电机驱动系统,取得了很好的节能效果。     

An improved CSI fed induction motor drive

Current source inverter (CSI) drives are preferred over voltage source inverter (VSI) drives in high power applications where fast dynamic response is not required. Conventional CSI drives have drawbacks such as resonance, instability at low speeds and high torque ripple, due to which their applications are restricted. This paper presents an improved CSI fed drive configuration that addresses these major drawbacks, as well as other power quality issues associated with the conventional drives. Two active power filters (APFs) are used in the proposed drive. The drive ensures sinusoidal waveforms at both the input and the output terminals. A simple CSI power circuit switching at fundamental frequency is used. Further, the use of a standard six-pulse SCR based rectifier eliminates the bulky and expensive input transformer, thus reducing the overall system cost. The proposed configuration is verified for a high power rating vector controlled induction motor drive. The design of the controllers and operation of the APFs are explained. Simulation results for the entire operating region of the drive including low speed operation and the field weakening region are presented. Finally, an important result regarding the presence of undesired circulating currents with the common DC bus for the two APFs, is also reported. The solution to avoid this problem is presented.     

一种用于异步电机效率优化的混合搜索方法

针对异步电机效率优化问题,提出了一种混合搜索方法.该方法起始于模糊自适应搜索,然后切换至黄金分割法以获取确定收敛速度.这样的搜索步骤能够降低转矩波动,避免在最优点附近发生振荡.利用一个包含铁损和机械损耗的异步电机模型,对该方法进行了矢量控制下的性能验证.仿真结果验证了该方法的有效性.     

考虑带泵类负载感应电动机影响的静态电压稳定性分析

为了更准确计及泵类负载机械特性对配电网静态电压稳定的影响,建立了一种将感应电动机T型等效电路与泵类负载机械特性相结合的感应电动机负荷模型。将其用于配电网潮流计算,采用前推回代法求解。进而将其用于连续潮流计算,建立了带泵类负载多台相同感应电动机的等效负荷模型,分析负荷连续增长对配电网静态电压稳定的影响。采用IEEE33节点算例对提出的模型与方法进行仿真验证,并与负荷按恒功率因数增加模型的连续潮流进行了对比。仿真计算验证了所提方法的合理性和有效性,表明采用该模型所得的静态电压稳定裕度要小于采用恒功率因数负荷计算结果,更接近工程实际情况。