电网电压三相不平衡时CVUF相角因素对异步电机运行性能影响

电网电压不平衡会对异步电动机的运行造成不良影响,因此研究三相电网电压不平衡时复数电压不平衡度(CVUF)的相角因素对异步电动机运行性能的影响。首先分析了三相绕组电压幅值、相位和CVUF间的关系,基于此,以1台5.5 kW Y132S-4异步电动机为例,在正序电压380 V、CVUF幅值恒定以及75%负载条件下,分析了CVUF相角因素对异步电机的定子电流、损耗、转矩性能的影响。结果表明:异步电机定子三相电流均随CVUF相角呈正弦规律变化,为避免带载能力下降过多及绕组过热,异步电机应避免运行在定子电流最大值处;CVUF相角对各项损耗、起动性能及稳态转矩脉动分量影响较小。最后计算了不同电压平衡条件下的异步电机三相定子电流和内部各项损耗,结果与实测结果基本一致,证明了理论分析的正确性。     

大型异步电动机状态监测与故障诊断系统的研制

介绍了大型异步电动机状态监测与故障诊断系统的主要功能及关键技术。该系统仅需采集异步电动机定子三相电压、三相电流瞬时信号，无需任何热或机械传感器，应用方便，运行效果理想。     

大功率异步电动机新型软起动装置的设计与实现

为了减小异步电动机起动过程中对电网的冲击、消除传统降压起动设备的有级触点控制对异步电动机的冲击、改善异步电动机的起动特性,基于电力电子技术对电动机软起动进行了研究。软起动装置是基于三相交流调压技术,通过改变晶闸管的触发角以调节定子两端的电压来实现的。采用双闭环控制的三相交流调压电路设计了50k W异步电动机软起动装置。内环电流控制及外环电压控制采用PI控制,实现了自动调节电动机起动电流,不但限制了电流,又使端电压平稳上升,实现了交流异步电动机平稳软起动。     

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.     

直接用外加电压建立三相异步电动机涡流场计算的数学模型

文章直接从电压源出发建立三相异步电动机在正弦稳态运行时的非线性复数有限元分析数学模型，将外加电压表征的定子电流公式与涡流方程联立求解，避免修正定子电流的电压迭代运算，从而提高了求解速度。     

测量对称负载有功功率的新方法

三相异步电动机功率的测量是三相异步电动机出厂试验的重要内容,介绍如何用三电压三电流法测量负载对称的三相异步电动机的输入功率,较详细地讨论了三电压三电流法测量三相异步电动机输入功率时的接线问题,并对测量原理及测量条件进行了分析。     

三相异步电动机外壳带电的原因

三相异步电动机金属外壳是不允许带电的,否则人触及就会发生电击、伤亡事故。三相异步电动机金属外壳带电现象归纳起来有如下情况： １、定子绕组绝缘损坏造成漏电。原因有：三相异步电动机使用时间太长,定于绕组绝缘老化;或者有异物进入电动机内部使定于绕组绝缘损坏;或者电动机长期过载发热使定于绕组烧坏;或者电源电压超过电动机的额定电压引起定子绕组绝缘击穿等。这些都可能使电动机的金属外壳带电。另外,如果电动机周围环境潮湿;或者电动机在雨雪侵袭下,水滴进入电动机内部;或者由于有害气体的侵蚀等。这些都会使三相定于绕…     

柔管钻机三相异步电动机的转矩测量

本文介绍了用测量定子电流及电压来测定三相异步电动机转矩的原理及方法,根据实验室模拟试验和现场实测的结果讨论了误差的来源及定量分析。该方法的特点是设备简单、易于实现,特别适用于不能用常规方法测量转矩的特种电动机,如柔管钻探电动机。     

三相异步电动机断电重合闸瞬态分析

分析和研究了三相异步电动机断电和重合闸的瞬态过程及危害。运用直接相量法建立了三相异步电动机的数学模型,并利用Ansoft语言建立了仿真模型。以一台三相异步电动机为例,仿真了电源断电后不同时间段重合闸时的电机瞬态过程,并给出了定子电流、转矩的瞬态曲线。通过仿真与理论相结合进行分析,得出在断电重合闸过程中,电机定子电流和转矩波动趋势。     

基于MM420变频器三相异步电动机无级调速的实现

变频器是工农业生产中常用的调速设备。通过MM420变频器对三相异步电动机进行控制,实现了三相异步电动机的无级调速控制。三相异步电动机无级调速可以通过变频器面板、模拟量电压控制、模拟量电流控制、PLC控制、EM Am06模拟量模块、Uss通信控制等方法实现。     

电动机动态相量法建模及对闪变传播的影响分析

提出了一种适用于电压闪变传播研究的感应电动机建模方法。该方法从三相感应电动机的电压方程、电磁转矩方程和基本运动方程出发,利用动态相量法建立了电源电压为波动电压情况下的感应电动机动态相量模型;实现了电动机定子电流的定量计算;并进一步分析了电动机参数对波动性定子电流和转子机械角速度的影响。利用定子电流计算公式,实现了电动机电压的定量计算;通过对比分析电源电压和电动机电压的均方根(RMS)值中的闪变频率分量,研究电动机负荷对闪变传播的影响,并给出了闪变传播系数的频率特性。结果表明,在绝大多数闪变频率下,电动机负荷对闪变具有抑制作用。仿真结果验证了理论分析的正确性。     

Analysis of Commutation of a Current Inverter Feeding an Induction Motor Load

A method for analyzing the performance of an induction motor fed from a current source inverter and especially for computing the currents during commutation of the inverter is presented. A mathematical model of an inverter-fed induction motor is given in terms of Park's vector. Based on this model a closed form time domain expression is developed for the current during commutation. The stator voltage of a current-controlled inverter-fed induction motor is shown to be almost sinusoidal with superimposed spikes during commutation of current. The computed performance of the machine is verified experimentally, and there is a very close agreement between the computed and test results. The method presented also provides information regarding the voltages across the commutating capacitors and thyristors based on which proper selection of the thyristors and commutating capacitors can be made.     

Protection of squirrel-cage induction motor utilizing instantaneouspower and phase information

A method of protecting a squirrel-cage induction motor by checking its condition before starting and while running is presented. The check before running is made by successively connecting the windings of the motor to an impulse generator and analyzing the resulting current and voltage. The running motor is checked by monitoring the AC-component of the power signals in all three phases, the sum of which gives information about the motor condition. The method presented is very sensitive to short circuits in the motor wiring, interturn short circuit, ground faults, and phase failure, but is not sensitive to load changes and small deviations in the supply voltage     

A simple method for detecting torque of an induction motor with a synchronous rectifier circuit

There are many torque measuring methods for an induction motor. Some applications require a simple and easy method to detect torque change rather than a precise method to measure the torque of the motor. The torque of an induction motor is roughly estimated by the input current. This is the simplest method of measuring torque. The input current of the induction motor is the sum of the torque current and the exciting current. The torque current is proportional to the synchronous wattage and the motor torque. The exciting current has a phase lag of almost 90° behind the torque current, is variable with the input voltage, and is larger than the torque current, especially at a light load. Therefore, it is difficult to find the motor torque from the input current of the motor at a light load. In this paper, we propose a simple and easy torque measuring method with a synchronous rectifier circuit. The synchronous rectifier circuit can find the vector component at the detection angle from the input current of the induction motor and can detect the torque current in the input current of the motor. By adjusting the detecting angle of the synchronous rectifier, the rectified signal is mixed with the torque current and the exciting current in proper proportions and compensated for the fluctuation of the input voltage. This serves as a simple and easy torque measuring method suitable for trouble detection at loads such as in life testing. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 83–90, 1999     

光伏水泵系统PWM输出滤波方法及影响分析

针对光伏水泵系统的逆变器PWM电压输出导致的共模电压、电流等现象常引起水泵电机故障的问题,在分析了PWM 逆变器驱动电机系统产生共模电压、电流机理的基础上,采用滤波电容公共点接回到光伏母线侧负端的LC滤波器,使共模电压与电流得到抑制。LC滤波器使电机侧的输入状态发生改变,通过分析PWM输出LC滤波方法对感应电机控制系统的影响,对滤除参数的选取进行了优化。并对以上研究进行了实验,结果表明参数选取方法的正确及有效性。     

感应电机软启动初始两相瞬态电流解析与控制

针对三相感应电机调压软启动初始时刻不对称过渡过程及电流冲击问题,给出了求解时域电流解析表达式的方法。该方法根据感应电机两相导通时的数学模型,通过频域和时域变换,得到了感应电机初始两相导通时定子电流与电机参数和晶闸管触发角之间的关系,并分析了不同的初始触发角对感应电机定子电流的影响,进而达到精确控制定子电流首半波峰值的目的。以一台2.2kW感应电机为例进行了实测和MATLAB仿真分析对比,验证了电流解析解的正确性。     

Quick regulation of sinusoidal output current in PWMconverter-inverter system

An induction motor drive system composed of a current output-type power converter and a current source inverter with sinusoidal input and output voltage/current is presented. Pulsewidth modulation (PWM) strategies with GTOs are applied to the converter and the inverter sections from the point of view of reduction of the current harmonics and suppression of the motor torque pulsations. A simple method for quick regulation of the AC output current amplitude is presented and applied to the PWM inverter section. To demonstrate the improvement in the current response of the inverter, a slip frequency/current regulation of an induction motor is considered. The experimental results of steady-state and dynamic operations of the motor are shown. The merits and demerits of this control method are discussed     

逆变器供电的感应电动机谐波转矩分析与计算

电压型逆变器输出的电压和电流波形中含有大量谐波,导致异步电动机低速时的转矩脉动和转速波动。文章在分析高次时间谐波产生的谐波脉动转矩基础上,介绍了用虚位移原理计算感应电动机谐波脉动转矩的方法。编制了感应电动机转矩的计算机程序,并用一计算实例对电动机谐波转矩进行了分析和计算。     

异步电动机调压节能控制器的设计

介绍了一种异步电动机的节能控制器的设计,通过实时检测电动机的电压、电流、功率因数,调节电动机的定子电压,使功率因数维持恒定,达到节能的目的,同时该控制器通过软件能对电动机进行保护.     

三相异步电动机测试系统设计

电机性能测试过程中经常需要调节被试电机的电压、电流以及改变电流互感器的倍率.对电机的电压、电流、转速等数据进行实时采集,需要采集的数据量大,并且需要快速准确的调节、控制和测量.介绍了一种稳定可行的电机性能自动测试系统;被试电机的电压调节及电流互感器的量程选择采用可编程逻辑控制器.