巴特沃斯低通滤波器在电动机测试中的应用

针对以往隐轴三相异步电动机转差率转速测量方法的弊端，阐述了笔者研制的转差率转速微机测试仪的特点、测试的依据、被测信号的获取及处理、测试系统的设计及工作原理，特别是巴特沃斯低通滤波器的应用进行了详细介绍。     

非接触式高精度多功能测速仪

转速、转差率与频率是各种电机测试常用的测定的数据。过去,对于很低的转速,很小的转差率及低频频率的测量方法比较落后,不能保证精度。为此我所于1981年研制成非接触式高精度多功能测速仪,并通过了技术鉴定,性能满足使用要求。     

转速、转差率和异步化同步发电机转子位置角的测量

介绍了转速、转差率和异步化同步发电机转子位置角的测量方法和硬件电路,简单介绍了以单片机为基础的基于ISA总线的工控机测量卡。     

HT-3型转差率转速测量仪简介

HT-3型转差率转速测量仪是上海电器科学研究所的科研成果,经转让给工厂生产后,于1985年4月通过了定型鉴定,现已正式投产(见本期封四广告)。测量异步电动机的转差率,过去一般都用闪光法,既不方便,精度也不够高。特别对高转差率电机和处于重负载时的多极电机,测量更感困难。HT-3型转差率转速仪是一种直读式数字仪表,具有三个功能:频率、转速和转差率的测量。     

异步机调速原理及转速公式探讨

与直流机相同,异步机转速是由理想空载转速和转速降合成。同步转速与理想空载转速的运动属性不同,两者没有直接、必然的联系。传统电机学导出的异步机转速表达式仍然是定义式,不能视为公式,更不能作为指导交流调速的理论依据。高效率调速的关键在于:在主磁通恒定的条件下,控制定子或转子的感应电势(E1或E2)以改变理想空载转速。异步机可等效于直流并激电动机,调速的关键在于使主磁通不变,相当于将并激电动机改变为它激电动机。串级、内馈、双馈调速和调压变频调速同属于电磁功率控制原理,性能一致,区别是控制对象不同。转差率和效率是完全不同的两个概念,不能用转差率变化与否来评价调速性能。转差率应具体区分为电转差率和静差率,前者影响理想空载转速,后者影响转速降。     

低效率电动机节能分析

三相交流异步电动机的效率越高,其转差率越小。也即在额定频率与电压下,相同负载的转速越高。对于某些功率与转速成正比,甚至成高次方比的负载来说,也就意味着电动机的输出功率的提高。反过来说,低效率电动机因其转差率的增大而使负载转速下降,就可使电动机的输出功率减少,从而达到节电目的。     

变频电机的转差率

<正>问异步电动机的转差率s=(n1-n)/n1(n1为定子旋转磁场转速,n为转子转速)。定子旋转磁场的转速和电网频率严格对应称为同步转速。请问,是不是变频电机在对应频率下的转速就是同步转速?不存在转差率问题?答变频电机上的电源频率不是电网频率50 Hz,而是可以在适当范围变动的变频器的频率。大多数变频电机还是采用一般的异步电动机,只是它的转     

用单板机测量异步机转差率

异步电机性能考核中,转差率测量是一个重要的试验项目,其试验方法一般有闪光法和测速法二种。前者在低转差时较准确,但测量时间较长,测得的转差率是一般时间内的平均值,当转差率高于6～7％时便不易测准。后者可直接测量电动机实际转速和电源频率,要求所测的转速精度较高,至少在0.1％以上,但需经计算才能得到结果。近年又发展了一种转差率数字测量仪,可用数字直接显示,使用方便,精度较高,但需要传感器和锁相倍频电路,结构和测量相当复杂,且仍不能解决低转差     

异步电动机Δ/Y降压运行时的转速稳定性

基于电磁转矩的实用表达式,分析了异步电动机分别带恒转矩、恒功率和离心式通风机性质三类典型负载的Δ/Y降压运行,得出其转差率和转速降落的计算方法,为校核降压引起的电动机转速降低是否满足运行要求提供了理论依据。     

等精度转速测量方法在磁悬浮飞轮中的应用

为解决传统转速测量方法难于满足磁悬浮飞轮系统转速测量的精度及抗干扰性能要求,提出了一种基于磁悬浮飞轮DSP控制器的等精度转速测量方法,给出了可测转速范围和测量精度的计算公式,分析了等精度转速测量方法的参数设置规律。应用等精度方法进行了转速测量实验,结果验证了应用等精度法进行磁悬浮飞轮转速测量的可行性及有效性,且具有精度高、抗干扰能力强、运算速度快等特点。     

汽车防抱制动系统车速测量技术的研究

实现基于滑移率控制的汽车防抱制动系统的前提是车速的准确测量.利用汽车轮速信号和车身加速度信号,建立了系统状态方程和测量方程,并用卡尔曼滤波技术来估计车速.为减少微控制器的计算量和增加系统可靠性,对四个轮速信号应用中值滤波方法,提出了一种实用的车速计算方法,试验结果验证了该方法的可行和有效性.     

塑壳式断路器新型智能化脱扣器的设计与实现

介绍了一种新型的塑壳式断路器智能化脱扣器。该智能脱扣器的硬件选用了低功耗、高速度的PIC16F877A型微控制器,并采用新型自供电方式,既有效地减小了电流测量误差,又减少了供电电路的发热现象。在软件方面,采用了三段保护算法,特别在瞬动保护中提出了一种基于改进型导数法加上三点滑动窗口的瞬动保护算法,可以达到可靠性与速动性的统一,有效兼顾了实时性和抗干扰性。实验表明,该脱扣器满足了要求,具有良好的性能。     

盘式永磁涡流驱动器的涡流软测量方法

针对永磁涡流驱动器导体盘在工作状态时无法直接测量涡流的问题,提出一种涡流软测量的方法。建立永磁涡流驱动器的解析计算二维模型,引入矢量磁位构建偏微分方程组,借助各层的边界条件,得到了导体铜盘涡流的解析解,从而得到导体铜盘上的涡流分布规律。采用该模型,永磁涡流驱动器在运行过程中所产生的涡流密度可以通过转差速度和气隙宽度的测量结果计算得到。之后应用涡流软测量模型,分析导体盘涡流密度大小随气隙宽度和转差速度变化的变化规律。所有计算得到的软测量结果都进行了基于有限元法的仿真验证。结果表明,涡流解析计算有较好的准确性,该软测量模型的结果平均误差约为2%,为永磁涡流驱动器运行过程中涡流的计算和产品优化设计提供了重要依据。     

Scalar controlled induction motor drive speed estimation by adaptive sliding window search of the power signal

This work reports an improved estimation reliability wide range rotor speed estimation algorithm for scalar controlled wound rotor induction machines using spectral search of the stator power signal. An adaptive sliding window speed estimation method is proposed that monitors the value of supply frequency to identify the optimum boundaries of the power signal narrowband maximised by a tracked speed dependent power harmonic, while adjusting to nominal slip variation with supply frequency change characteristic of scalar controlled machines. Analytical expressions are derived that allow direct correlation of the surveyed spectral window boundaries to supply frequency. Once identified, the optimal power spectral narrowband enables supply frequency independent speed evaluation. The proposed method is underpinned by a dichotomous search based frequency tracking technique enabling improvement in the attainable estimation rate. The presented technique’s performance and limitations are assessed in steady-state and transient operation real-time experiments on two different scalar controlled 7.5 kW machines. The scheme is shown to provide competent real-time speed estimation in a wide operating speed range for lower dynamics transients and steady-state operation.     

Some Electronic Techniques for Speed and Slip Measurement in Power Laboratories

Circuits that provide a transient and steady-state measure of slip and speed for rotating machines are described. A basic stroboscope consisting of very few components, all solid state, is also described and this can be used for the measurement, under steady conditions, of synchronous machine load-angle, of speed, and also, to a limited extent, of slip. The circuit designs are modular in character and where possible integrated circuits have been used, so that students may reasonably be able to understand not only the principle of the equipment but also, when educationally desirable, something of the circuitry as well. A further objective in developing these measuring devices has been simplicity of construction and economy of components so that multiple facilities can be provided for power teaching laboratories at a minimal cost.     

Analysis of three-phase induction motors utilizing `The IodekiceLocus'-a normalized impedance circle

A method that allows students to analyze the performance of any three-phase induction motor operating at any arbitrary speed, either analytically or graphically, using the same conceptual approach is presented. The method uses a unity-diameter normalized impedance circle with a periphery calibrated in terms of normalized slip, which is defined as the ratio of per unit slip to a readily determined machine constant. Equations that allow the tabulation of the real and imaginery impedance components of the normalized circle as a function of normalized slip are developed. These data may be plotted for use with graphical analysis or used directly in a simplified mathematical analysis. The key factor in the development is shown to be the concept of normalized slip. Using this concept, the specific operating point of a machine can be simply and uniquely determined for any given value of per unit slip     

火箭测控系统中的实时处理方法及容错分析

本文介绍了火箭测控系统中采用的双体ＲＡＭ实时处理方法,并对同步码的模糊识别及三取二算法的容错能力进行了详细的分析。     

辊道电机出现断轴现象分析

以 YG1 2 5Z-4　 1 .3k W电机为例分析了断轴原因 ,指出辊道电机采用转速开环恒压频比控制的调速系统当电机转差率不同时存在的问题 ,并给出解决问题的方法。     

异步电机按定子磁场定向的转差频率控制

在分析现有转差频率控制方案优缺点的基础上，提出一种按定子磁场定向的转差频率控制方案。利用坐标变换和磁场定向原理，建立按定子磁场定向的异步电机数学模型。新系统通过定子电压直轴分量直接控制定子磁链的变化率；在转速通道中，电流调节器的输出作为转差频率，继承了标量型转差频率控制方案的优点。新系统的动态控制算法不依赖于转子电阻和电感参数。结果表明，新系统具有良好的静、动态性能和鲁性棒。     

Sensorless vector controlled converter for variable speed wind generation system using an induction generator

This paper proposed two types of speed sensorless converters that can control rotational speed and electric power. One is based on a slip frequency control system. The other is based on a vector control system. The rotational speed of the wind turbine is estimated with the phase voltage and phase current of the induction generator by the adaptive rotor flux observer. The estimated wind turbine rotational speed ω_r^est is used as the feedback of the speed control loop in the converter control system. Also, the estimated rotor flux ?_2d^est is used for the vector control. The simulation results confirm that both of them perform satisfactorily under the speed sensorless operation. The method based on the vector control system generates more electrical energy than does the method based on the slip frequency control system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 62–75, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20323