笼型异步发电机在小风电系统中的励磁运用

针对小型永磁同步发电机输出电压随风速变化而同趋势变化,无法自我调节等不足．提出了一种全新的集电力电子技术、控制技术及鼠笼异步发电机于一体的动态励磁方法,即经济可靠的笼型异步发电机结合应用SVG（静止无功发生器）技术的方法。结合物理实验与算例,对笼型异步发电机在离网运行时的励磁特点进行了分析,并通过与永磁同步发电机在有效风速工作范围和整体效率等方面的对比．得出了在小型离网风力发电系统中应用笼型异步发电机,相对永磁同步发电机有诸多优点,有着很好的应用前景。     

Influence of Induction Motor Design Data on Effects of Cage Asymmetry

The purpose of this paper is to analyze influence of design data on a component （1 - 2s）~ in stator currents of induction motors, mainly used for cage fault diagnosis. This paper shows that such an approach does not always lead to a correct outcome. The considerations are based on a ＂classical＂ model of induction motors extended to cage asymmetry by introducing cage asymmetry factors ko~ and ka. It has been found that in order to estimate the level of the component （1 - 2s）7~, it is enough to know the pole-pair number ＂p＂ and the number of rotor slots ＂N＂. The main objective of the paper is to provide engineers with simple qualitative prediction of effects due to cage faults for various motors when information on design data is very limited.     

Behavior of the Three-Phase Induction Motor With Spiral Sheet Rotor

Improvements in torque at low currents using a rotor with spiral sheets are analyzed. Several rotors and stators have been built combining different constructive and mechanical characteristics of the related elements: inertias, constructive materials, geometrical shapes of the sheets, and geometrical disposition of the sheets. These different types of motors have been simulated using computer-aided tools and then tested in the laboratory. Finally, four stators (1000, 1500, 1500-type A, and 3000 r/min), with the same constructive parameters, have been simulated and tested with the following rotors types: solid rotor, solid rotor with diamagnetic rings, drag cup, and simple and double squirrel cage rotor; the results have been compared to those obtained with the seven variants of the spiral sheet rotor presented in this paper.      

Thermal Analysis of a Small,Totally Enclosed,Fan-Cooled Induction Motor

Abstract

Improving cooling performance is a key factor when developing induction motors in smaller sizes with larger capacities and higher rotational speeds. Doing so, however, requires thermal analysis to discover the major parameters in the cooling design. This study investigates temperature distributions and heat transfer rates in a small, totally enclosed, fan-cooled induction motor with both numerical and experimental methods. Parametric studies show that (1) the frame is of the utmost importance in the design and (2) that cooling the motor close to stator coils is the most effective method for cooling. Quantitative analyses show the relationship between the size of the motor and the rise in coil temperature.

The results from transient and steady-state experiments using a real motor show that (1) the hottest spot is in the rotor surface, and (2) the load-side surface has a higher temperature than that of the fan-side. The hottest spot in the stator coils is the outer surface of the load-side endwinding. The coil temperature is also significantly affected by the attached components of the frame, as well as the contact state between the stator iron and the frame. It is recommended that the current outer fan be redesigned to improve cooling performance.     

High-Frequency Loss Calculation in a Smooth Rotor Induction Motor Using FEM

In this paper, a new approach for the calculation of high-frequency losses in induction motors is presented. The input to the motors is assumed to be supplied from a sinusoidal voltage source. The method is based on the two-dimensional (2-D) field solutions of the magnetic circuit, obtained by using a nonlinear ldquoharmonicrdquo solution. Hence, the solution time is very short. From the ldquoharmonicrdquo solution, the air-gap field distribution as well as the fundamental frequency eddy current losses are determined. The high-frequency loss calculation is based on the assumption of a path for eddy currents within a lamination. A constant k is introduced that defines the width of the current flow path. The empirically found k value is verified by a theoretical calculation. The new method is applied to the calculation of losses of two smooth rotor induction motors. The prediction accuracy is found to be very good. The method is also applied to two open rotor slot motors to observe the change in the prediction accuracy. It is found that due to the small slot openings accurate predictions are still possible. The approach presented in this paper requires little time for loss calculation, and is very suitable for minimizing losses at the design stage.     

Performance of a Doubly-Fed Induction Motor with Controlled Rotor Voltage Magnitude and Phase Angle

The performace of a doubly-fed induction motor (DFM) controlled by a voltage phasor at the rotor side is investigated. This voltage has two control parameters: the magnitude and the phase angle. By controlling each one of these two parameters, it is possible to produce the appropriate voltage phasor which must be applied to the induction motor slip rings for achieving certain operation, i.e. any function of load power versus speed. The electromagnetic characteristics in the steady state are determined when the voltage magnitude and its phase angle varies from zero to their upper limits. These limits are dictated by improving performance considerations.     

汽轮机转子热稳定性试验干扰因素分析

汽轮机转子热稳定性试验由于干扰因素的存在,使得测试得到的数据带有很大的波动,影响试验结果的准确性。对此问题,分别从试验转子的运动状态以及测试信号的频率成分两个方面分析论证,得到了试验的主要干扰来自支持轴承跳动的结论。根据分析论证的结果,一方面对支持轴承采取了紧固及更换措施,大幅减弱了试验干扰;另一方面也证明了采用求平均值的方法进行数据处理、消除干扰是正确的、有效的。通过采取以上两个措施,提高了试验结果的准确性。     

叶片高频淬火

对７００ｍｍ末缘和４６０ｍｍ次末级叶片进汽边局部高步各的工艺方法、淬硬区的技术要求、主要工艺参数、淬硬层的金相组织、淬火热影响区的分布等方面作了较为全面的说明。本文提供的资料表明：叶片采用高频感应淬火,提高了叶片水蚀区的敏感硬度,能显著改善叶片的抗水蚀,且工艺简单,成本低廉,是叶片抗水蚀有效而经济的手段。     

Solving the More Difficult Aspects of Electric Motor Thermal Analysis in Small and Medium Size Industrial Induction Motors

With the ever-increasing pressure on electric motor manufacturers to develop smaller and more efficient electric motors, there is a need for more thermal analysis in parallel with the traditional electromagnetic design. Attention to the thermal design can be rewarded by major improvements in the overall performance. Technical papers published to date highlight a number of thermal design issues that are difficult to analyze. This paper reviews some of these issues and gives advice on how to deal with them when developing algorithms for inclusion in design software.     

A Reconfigurable Motor for Experimental Emulation of Stator Winding Interturn and Broken Bar Faults in Polyphase Induction Machines

The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished.      

Analysis of Critical-Speed Increase of Induction Machines via Winding Reconfiguration With Solid-State Switches

Commonly used speed-control concepts permit speed ranges up to two–three times the base speed via voltage to frequency ($V$/$f$ ), that is, field-weakening control. This paper teaches the extension of the speed-control range up to nine times the base speed through online reconfiguration of the motor windings via electronic switches. The switchover of the windings, either from a winding with $p_{1}$ poles to $p_{2}$ poles, or from series to parallel connection of the number of turns per phase—so-called ($V$/ $N$·$f$) control—lasts less than a 60-Hz cycle. Such fast switchover causes small transients only, and therefore, this concept is applicable to most variable-speed drives.      

Double-Winding Rotary-Linear Induction Motor

A rotary-linear induction motor whose stator possesses two windings generating the rotating and travelling fields is described. A theoretical analysis of the magnetic field and motor performance takes into account finite stator length effects. Computational results are partially verified by experimental measurements of the motor's model.     

Measured Winding Impedances of a Large A-C Motor

This paper presents measured R, L, C, G parameters of the stator winding of a large A-C motor. The values of these parameters were determined within the frequency range from 100 Hz up to 10 MHz with a high quality impedance analyzer. Twenty different measurements of the R, L, C, G parameters of turns, coils and phases are reported. The results should be of help to utility engineers concerned with turn insulation breakdown and surge protection of large A-C motors. The presented data can be used as an aid in development and calibration of wave propagation models needed for computation of electromagnetic transients in the windings of rotating machines. Ontario Hydro's assistance in this work and EPRI's funding are gratefully acknowledged.     

折返式鼠笼弹性支承刚度试验技术研究

为准确测量折返式鼠笼弹性支承的刚度,在对其进行数值分析的基础上,设计了自动控制刚度试验系统,根据试验数据分析不同的位移传感器、不同的施力位置、测点位置和力施加速度对支承刚度试验值的影响。研究表明:数值仿真得到的鼠笼弹性支承变形规律与试验测试结果一致,折返套尾端位移比折返处大,且位移与施加的力呈线性关系;不同直径的电涡流传感器测得的刚度与电子千分表相比,最大偏差为10.17%;折返处的刚度测量值稳定性好,力施加位置改变时刚度测量值的最大变化幅度仅为2%,而折返套尾部刚度的最大变化幅度达到20.6%;力施加速度小于60 N/s时其对刚度试验值影响很小。     

汽轮机转子的传热分析和热应力计算

详细给出了某300MW机型的汽轮机转子温度分布计算方法,推导了应力计算模型并定义了有效温差的概念,由此可将汽轮机应力控制问题转化成有效温差的控制问题,对实际应用具有重要意义。     

The Hysteresis Motor with an Anisotropic Rotor

An analysis of the hysterezis motor with anisotropic rotor has been carried out. Using an elliptical approximation for the hysteresis loop, the expression of the magnetic vector potential in the anisotropic region of the rotor has been obtained both in the case of a stator surface carrying a curent sheet with sinusoidal variation, and in the case of a rotor surface at which the normal component of the flux density has a sinusoidal variation. The relationships established allow to study the dependence of the electromagnetic torque upon the thickness of the anisotropic region made of hysteresis material, the characteristics of the hysteresis material and the degree of anisotropy. The rotor parameters have been studied and an equivalent circuit has been derived in the case of a three-phase motor.     

Characteristics and Performance Analysis of a Permanent-Magnet Motor with a Multistacked Imbricated Rotor

The paper studies the parameters and performance of a motor with a multistacked imbricated permanent magnet rotor. An experimental motor with ferrites for excitation is used in the investigation. Methods used in the determination of the parameters, Xd, Xq and the core-loss component, Rc, are described. Their variation with load and terminal voltage are also discussed. These parameters are applied in a model based on the classical two-axis machine theory for performance analysis. Detailed investigation shows that the reactance characteristics under steady-state conditions are similar to a wound rotor machine. Computed results using these values of Xd, Xq and Rc show agreement with experimental results. The significance of Rc is noted.     

基于F级燃气轮机透平转子的热分析数值模拟

以某型F级燃气轮机透平转子为研究对象,采用适用于透平转子热分析的物理建模方法,通过增加部分动叶和隔板结构,准确模拟透平盘顶部的热量传递。应用ANSYS软件完成了透平转子换热和热-结构耦合的数值模拟,确定了工程上透平转子热分析的流程及相应的收敛准则,具有较高的工程应用价值。     

600MW汽轮机转子热应力及寿命损耗分析研究

以某电厂600MW超超临界机组汽轮机转子为研究对象,运用ansys有限元软件建立二维模型,计算出不同平均温升率下机组启动时转子热应力值。与理论公式通过最小二乘法进行曲线拟合,从而确定无中心孔转子的时间修正因子和形状因子。然后根据低周疲劳曲线计算出转子的寿命损耗。鉴于波动、间歇式新能源的并网,能够指导运行人员,通过温升率和温升量的调节,在安全的前提下,提高汽轮机组负荷变动能力和调峰能力。