继电保护柜接线端子安装紧固扭矩试验研究

针对继电保护柜在现场安装阶段接线端子与导线连接紧固施工工艺没有明确标准规范的现状,依托南京西环网UPFC工程建设需求,试验研究了继电保护控制柜上的普通和电流电压2种端子及其配合导线连接组在不同紧固扭矩下的回路电阻、拉脱力、以及导线和端子紧固螺栓的受损情况,提出继电保护柜接线端子安装紧固扭矩工艺规范为:继电保护柜上的接线端子必须采用扭矩螺丝刀进行紧固安装,而且扭矩螺丝刀的刀头尺寸必须与螺栓的槽口尺寸相一致。继电保护柜上普通端子的接线紧固扭矩值设置为0.5 N·m、电流电压端子的接线紧固扭矩值设置为0.7 N·m为宜。     

某换流站电压互感器接线端子断裂分析

某换流站电压互感器接线端子发生断裂,对接线端子进行尺寸测量、光谱分析、渗透检测、弯曲试验、断口分析、受力分析,最终分析得出接线端子设计时未考虑疲劳工况,从而导致接线端子发生疲劳断裂。     

PWM变频调速电动机端子上电流特性的研究

研究了ＰＷＭ变频调速电动机端子上的电流特性,测量了驱动系统中各连接点的电流波形,特别是由陡上升沿电压引起的高频尖峰电流分量的特性,同时也研究了电缆长度及滤波器对驱动系统中各连接点的电流波形的影响,从理论上分析和讨论了电动机绕组的电流特性与其电压分布特性的关系,提出了改善绕组电压分布的初步措施。     

国外电机制造专利文摘

直流电机该发明的目的,在于改善与励磁无关的整流条件和直流电机的特性。线路如下图所示。电枢绕组1与换向极绕组2串联。激磁绕组接在主极上,其一端经调节电阻接于他激电源的接线端子4上,而另一端接在换相极绕组接线端6上,端子7与他激电源的另一端8相联。这种接线,改变电枢回路的电流,就要引起换向极绕组2的电压变化,并且其变化对换向极的作用与他激电源的作用一致。由于该电压的作用,在激磁回路里     

PWM变频调速电动机端子上过电压的抑制

脉宽调制（PWM）变频器输出的陡上升沿且高重复的脉冲电压在长电缆的末端发生波反射而产生近似2倍的尖峰过电压,从而导致变频调速系统中电动机绝缘的过早损坏。采用RC一阶阻尼滤波器来抑制PWM变频调速电动机端子上的尖峰过电压,首先研究了在不同电缆长度（30m和75m)下,滤波器的电阻和电容对电动机端电压特性的影响,得到了电缆长度、滤波器的电阻和电容与电动机端过电压幅值及脉冲电压上升沿时间的关系,结果表明滤波器的电阻值越小,电容值越大,则电动机端子上过电压幅值就越小,且脉冲电压上升沿时间也越大。为了减小滤波器的功耗,其电容值应选择小于0．1μF。当滤波器的电阻参数小于电缆波阻抗的1．5倍,且电容参数选择在0．02－0．1μF之间时,电动机端子上的过电压倍率则不超过1．2。最后应用传输线理论及信号的卷积分对试验结果进行了分析,并得出电动机端子上过电压的上升沿由快变区和慢变区两段组成。     

零序电流方向保护一次误动作的分析

凡新安装或一、二次接线经过变动的方向零序保护,其零序功率方向元件必须利用负荷电流和工作电压检查其接线的正确性。 因为被保护线路发生接地短路时,保护安装处所出现的零序电流和电压相位关系是:零序电流超前零序电压约为110°,而功率方向元件动作特性的最大灵敏角为电流落后电压约70°。因此当继电器的电流端子为正接时,则电压端子必须与电压互感器零序电压反极性相     

滤波器对PWM变频调速电动机端子上电压波形的影响

本研究了滤波器的参数对电动机端子上电压特性的影响,得到了电缆长度,滤波器的电阻和电容与电动机端过电压幅值及脉冲上升沿时间的关系,给出了滤波器参数的选择范围,并对试验结果进行了讨论和分析。     

用C语言编写大电动机起动时电压水平计算程序

电气工程师通常要认真地计算大电动机起动瞬间配电母线上和电动机受电端子的电压水平 ,以确定母线上的电压水平是否符合规程要求 ,并确定电动机端子电压能否满足电动机直接起动的要求。手工计算工作量很大 ,且难免出现误差。笔者认为编制电算程序能弥补手工计算固有的不足 ,本文对此加以介绍。1　相关规范现行国家标准《通用用电设备配电设计规范》(GB5 0 0 5 5 -93 )中有关电动机起动的内容如下 :第 2 .3 .1条　电动机起动时 ,其端子电压应能保证机械要求的起动转矩 ,且在配电系统中引起的电压波动不应妨碍其他用电设备的工作。第 2 .3 .2…     

增安型无刷励磁同步电动机接线盒的设计

本文介绍了增安型无刷励磁同步电动机接线盒结构设计情况及采取的措施,同时对接线端子冷挤压工艺问题进行了探讨。     

补偿法消除电压互感器二次回路压降的探讨

1 概述 在发电厂、变电所和大型电力用户的高压电能计量装置中,运行中的电压互感器二次接线端子往往离装设于控制室配电盘上的电能表有较长的距离,且中间还有开关、保险管和接线端子排,在这种情况下,电压互感器二次回路上必然会产生一定的电压降,这一电压降的大小与以下诸因素有关: (1)电缆线连接过程中所接开关和保险管     

PWM逆变器供电异步电机端部过电压的分析和仿真

PWM逆变器供电时电机的端电压出现幅值增高和振荡现象,对电机的匝间绝缘造成很大的威胁,本文提出了一种可以判断PWM逆变器供电异步电机端部过电压波形的实用仿真方法,该方法根据PWM逆变器供电电机系统的特征建立系统的仿真模型,将电机用实测的等效的阻抗频率特性来替代,将三相电缆等效成一个二端口网络,通过傅立叶分析计算电机端部的暂态过电压。与实测波形的对比,证明这种方法的仿真结果可以与实际情况良好地吻合。     

Estimation and Reduction of Motor Input Surge Voltage Using Frequency Response Analysis

This paper presents a plain method of calculating the voltage waveform at motor input terminals from the inverter output terminal voltage and also a method of reducing the voltage. The voltage waveform at the motor input terminals is obtained by a frequency domain calculation using the transfer function of the cable and the frequency characteristics of the voltage waveform at the inverter output terminals. The analysis using this method clarifies the mechanism of the rise of the maximum voltage at the motor input terminals, that is, ringing at the motor input terminals, which occurs at specific frequencies at which the transfer gain increases, causing the rise of the maximum voltage. Therefore, to decrease the maximum voltage at the motor input terminals, it is effective to shorten the cable length or cancel the ringing voltage by preswitching. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 11–19, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22482     

电缆长度对PWM逆变器驱动电机端电压的影响

在建立PWM逆变器－电缆－电机高频模型基础上，通过仿真电机端子上的PWM脉冲反射波瞬间电压，建立了反射波峰值电压与电缆长度之间的关系，并给出了不同电缆长度情况下电机端电压的仿真及实验波形。     

基于多电平技术的电机端子过电压研究

两电平逆变器输出电压跳变很大,在逆变器与电机长电缆连接情况下,引起电机端子过电压。多电平逆变器可以很好改善输出波形,减少电压跳变。考虑多电平技术在抑制电机端子过电压中的应用,首先建立了连接逆变器和电机电缆的二端口集总参数模型,在此模型的基础上分别推导两电平脉冲和三电平脉冲在电机端产生的电压时间表达式,分析了采用多电平技术抑制过电压的机理。最后用Matlab/Simulink进行建模仿真验证多电平技术抑制电机端过电压的有效性。     

Improved current source GTO inverter-fed induction motor driveswith PWM-controlled thyristor converter

An improved current-source GTO (gate turn-off) inverter system for driving an induction motor at high frequency was developed. This system is composed of an inverter using GTOs and a PWM (pulsewidth-modulated)-controlled thyristor rectifier. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier and to apply PWM control techniques. This circuit plays an important role in the treatment of reactive power in a load. The capacitors connected to the AC input terminal to improve PWM control also function as a filter. Thus, the waveforms of the input voltage and current become almost sinusoidal. Principles and circuit operations of the rectifier section are described in detail. The current-source GTO inverter is used to drive a 5.5 kW induction motor. The experimental waveform and characteristics for the tested motor drives are given. It is shown that the harmonic components of the input voltage and current are eliminated or reduced by using the PWM control technique without spoiling the inherent characteristics of the current-source GTO inverter     

Design considerations for an inverter output filter to mitigate theeffects of long motor leads in ASD applications

Design considerations for an inverter output filter to mitigate the effects of long motor leads in adjustable-speed drive (ASD) applications are presented. It is shown by analysis that, for a given length of cable, reducing the dv/dt of the pulsewidth modulated (PWM) inverter output voltage applied to the cable below a critical value will eliminate overvoltages due to voltage reflections. Design issues for a low-pass filter at the inverter output terminals to reduce the dv/dt of the inverter output pulse are examined in detail. The filter operation is verified for the entire variable frequency range of the inverter. The performance of the filter is evaluated through simulations and experimentally on a 460 V commercially available AC motor drive (PWM insulated gate bipolar transistor (IGBT)). The proposed inverter output filter is then compared with a motor terminal shunt filter also designed to reduce overvoltages and ringing at the motor terminals     

对变频电源供电电动机的技术分析

作为变频器供电的电动机,由于变频器在换流过程中电动机释放电感贮能引起电压突变,叠加在运行电压上,而产生冲击电压,同时将使电动机上的电流波形呈现为一个叠加谐波的正弦波,该谐波电流将使异步电动机的磁路中产生一个脉动的磁通分量,此磁通分量叠加在主磁通上,使电机损耗增加,产生电磁振动和噪声,并产生对电机绝缘的冲击电压及轴电压,对电动机的对地绝缘形成威胁。对变频电源供电电动机产生的技术问题及解决办法做了详实的论述。     

PWM逆变器-感应电机系统中的过电压抑止滤波器研究

在PWM逆变器供电的感应电机调速系统中，当逆变器与电机之间的电缆超过一定长度后，在电机端可能出现2倍于逆变器直流母线电压的过电压。本文从时域和频域分析了过电压的内在特点，给出了过电压振荡频率与系统参数的函数关系式，根据过电压的形成机理及其特点，以R－C滤波器为例，给出了详细的滤波器参数选取方法。仿真和实验结果证明了按照本文所提供的方法设计的滤波器能够很好地抑止电机过电压。     

Characteristics of an induction motor with reduced turns of terminal coils

The use of PWM inverters with high switching characteristics for the adjustable speed drive system causes an overvoltage with steep‐fronted waveform on the motor terminals. As this steep‐fronted transient voltage in inverter drive loads heavily on the terminal coils of motor winding, the insulation failure in the motor winding occurs mostly on the terminal coils. Therefore, it is reasonable to reduce the turns of terminal coils only and to increase the dielectric strength of interturn insulation. This paper presents a comparison of measured characteristics of normal induction motors and induction motors with reduced turns of terminal coils and also a comparison of the results measured and calculated by equivalent circuit. The appropriate rate of reduced turns of terminal coils is about 20%. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 49–56, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10093     

A New Current Source GTO Inverter with Sinusoidal Output Voltage and Current

A new current source inverter with sinusoidal output voltage and current is presented. Gate turn-off thyristors (GTO's) and pulsewidth modulation (PWM) control techniques are used in the current source inverter to produce the sinusoidal output voltage and current. Three capacitors are connected to the ac output terminals to absorb overvoltages which occur when the GTO current is cut off and to provide a filter function for reducing harmonics in the output current. Voltage spikes, which have been a serious problem in the practical application of this inverter, are suppressed by adding gate pulses which force the inverter into a state of shoot-through. Moreover, this inverter permits the capacitance of an ac output terminal capacitor for absorbing overvoltages to be reduced to one-tenth or less of that of a commutating capacitor in a conventional thyristor type current source inverter. A 3.7-kW induction motor is driven by the inverter. The motor efficiency and noise level are measured and compared with those obtained when the motor is driven by a conventional voltage source PWM inverter. An operating efficiency five or six percent higher and noise level 10 dB lower are obtained for the former. Therefore, this current source GTO inverter is very suitable for ac motor variable speed drives.