基于最小电流模糊控制的电机软起动

通过分析电机软起动的工作原理可知，影响电机起动特性的关键是晶闸管的初始触发角和动态过程中触发角的增量。基于此，提出了最小电流的模糊控制方法。以电流和电流的变化为输入量，通过模糊控制得到晶闸管的触发角，使电机可靠起动，同时通过最小电流控制实现节能。     

晶闸管控制异步电机软启动过程中振荡现象研究

针对晶闸管控制的异步电机在轻载软启动过程中常会出现的电流以及转速振荡现象,建立了异步电机软启动通用仿真模型,并对该软启动过程中的振荡现象进行仿真.分析了软启动中电机的启动电压以及电机的机械特性并研究了电机在软启动过程中产生振荡现象的因素和原因.实施了在电机软启动控制系统中,应用晶闸管续流角闭环反馈控制的策略.实验证明,...     

基于分级变频软起动器中功率因数角闭环控制的研究

研究了三相交流异步电动机分级变频起动的起动方法,并分析了电机在软起动调压过程中产生电流振荡的原因。提出了在电机分级变频软起动器控制系统中应实施电动机功率因数角闭环控制的观点,通过分析指出:晶闸管调压电路中可控的晶闸管触发角应该由两部分组成,一部分是按预定规律调整的角度,另一部分是跟随电机功率因数角的变化而增加的动态调整角度。该方法可以使电动机起动过程中的电磁转矩和电流脉动得到明显的抑制。     

异步电动机的模糊软起动仿真

针对交流异步电动机直接起动电流过大的问题,设计了带电流闭环的电子控制模糊软启动器,该软起动器可以限制起动电流,减少起动过程中电流过大对电网和设备的损坏.根据电机起动过程中反馈电流与晶闸管触发角之间没有精确的数学模型,且存在非线性时变的特性,本文采用模糊控制方法,建立模糊控制器,从而减少起动电流,改善电机的起动性能.仿真...     

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。     

电机软起动控制系统中功率因数角的研究

该文研究了三异步电动机功率因数角随转变的变化规律，根据晶闸管调压电路的工作特点，分析了电机在调压起动过程中产生电流振荡的, 在电机软起动控制系统中应实施电机功率因数角闭环控制的观点，通过分析指出：晶闸管调压电路中可控的晶闸管触发角应该由两部分组成，一部分是按预定规律调整的角度，另一部分是跟随电机功率因数角度的变化而增加的动态调整角度。实验证明，在闭环控制方法有效地解决了电机软起动过程中的电流震荡问题，同时，利用实时检测到的功率因数角信息，可以实现电机的轻载节能运行功能。     

晶闸管调压恒电流起动特性的分析与计算

对于晶闸管调压器用于异步电动机软起动的特性参数和控制方法进行了分析，提供了恒电流起动过程中起动时间和电压率的计算方法，给出了晶闸管触发角，控制电压的计算步骤，给定电路的原理接线图及有关电机的计算和实验结果，对于异步电动机软起动装置的设计与调试具有一定的指导作用。     

晶闸管调压恒电流起动特性的分析与计算

对于晶闸管调压器用于异步电动机软起动的特性参数和控制方法进行了分析，提供了恒电流起动过程中起动时间和电压率的计算方法，给出了晶闸管触发角、控制电压的计算步骤，给定电路的原理接线图及有关电机的计算和实验结果。对于异步电动机软起动装置的设计与调试具有一定的指导作用     

10 kV对旋风机软启动及触发技术研究

常规的晶闸管斜坡调压软启动方式和晶闸管触发系统对10 kV系统下的异步电机难以获得良好的启动效果.为此提出了基于续流角增量的定子电压补偿方法和模糊恒流启动控制方式,基本消除了大功率电机启动过程中的电流过大和电流振荡.晶闸管采用高频电流源触发,解决高压侧和低压侧隔离触发的问题.基于以上方法的新型软启动器在10 kV对旋风机上获得了不错的应用效果.     

感应电机软起动新技术

文中提出的控制策略用于感应电机的启动过程中。通过控制晶闸管组成的三相交流调压电路，使其输出电压和频率的比率接近常数．从而使感应电机启动过程中保持低电流的同时可以产生较大转矩。还通过仿真，同传统软起动方法的性能上做了比较分析。     

异步电动机软起动装置中管压降信号的检测与触发电路

阐述了三相异步电动机软起动装置中晶闸管管压降信号的检测方法及其应用 ,针对三相异步电动机软起动结束后管压降信号难以检测的问题 ,提出了一种采用 80C1 96KC单片机和可编程逻辑器件GAL1 6V 8构成的触发电路 ,该电路可以确保异步电动机起动结束后晶闸管管压降信号的检测。     

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.     

基于晶闸管模糊控制的电动机软起动研究

传统降压起动方式会对电动机本身、拖动设备及电源设备的使用寿命有很大的影响,同时对电网电压也造成很大的冲击,影响同一电网其他电气设备的正常运行.为了解决上述问题,本文研究了三相感应电动机软起动器.主电路由三组反并联的晶闸管构成,通过控制晶闸管的触发角,降低电动机定子电压,从而达到抑制起动电流冲击的目的.对交流调压电路进行...     

Static Exciters for Induction Generators

The utilization of the squirrel cage induction motor as an autonomous induction generator is briefly reviewed. In view of potential new applications, the discussion focuses on a simple exciter scheme based on using a static reactive power generator implemented with fixed capacitors and thyristor controlled inductors. The feasibility of the proposed scheme with naturally commutated thyristors is verified by measurements on a test setup employing a standard 15-hp induction motor.     

异步电动机软起动器的研究

异步电动机软起动器以其软起动能力和其他一些优点而广泛用于起动异步电动机。本文分析了异步电动机软起动器的电路结构。介绍了一种利用晶闸管两端电压信号来确定软起动结束点的方法。提出了在异步电动机供电不平衡的情况下平衡相间电流的方法,给出了晶闸管故障检测的方法。     

A Current Source GTO Inverter with Sinusoidal Inputs and Outputs

With the application of gate turn-off thyristors (GTO's) and PWM control techniques, a current source inverter capable of producing sinusoidal input/output (I/O) voltages and currents has been developed. The sinusoidally modulated current is fed to the GTO's in the rectifier and inverter sections. The overvoltage-absorption capacitors connected to the ac input and output terminals function as a filter and, consequently, the waveforms of the input/output voltages and currents become sinusoidal. Because the PWM control utilizes the high-speed switching characteristics of the GTO's, the dc link current smoothing reactor and the overvoltage absorption capacitors are greatly reduced. The dc link voltage in the rectifier section is controlled to adjust the ac motor current. This is accomplished by using the firing angle shift method in conjunction with the method involving varying the width of the bypass gate pulses, which put the rectifier section into a bypass state. The current source GTO inverter is used to drive an 11-kW induction motor. As a result, excellent acceleration and deceleration characteristics are obtained, which verifies that the new current source inverter is quite suitable for driving an ac motor at variable speeds.     

A Comparative Study of Symmetrical Three-Phase Circuits for Phase-Controlled AC Motor Drives

The speed of an induction motor in certain types of drives can be adjusted by phase control of the applied voltage. Three pairs of inverse-parallel thyristors are required for three-phase bipolar symmetry, but several different arrangements of the thyristors and motor windings are possible. A direct series connection of thyristors and windings in each phase can be made; the three phases can then be connected in delta, wye, or wye with neutral return. Alternatively, a delta connection of thyristor modules can be inserted in the opened neutral junction of wye-connected windings. Representation of the motor as a counter EMF in series with leakage reactance allows a simplified analysis of the current waveforms in terms of the thyristor conduction angle. With a given fundamental current, the current harmonics in the motor windings and in the supply lines for each of the circuits can then be compared. The results are equally applicable to thyristor-controlled inductive loads such as may be used for reactive power adjustment.     

Design and performance of a digitally based voltage controller forcorrecting phase unbalance in induction machines

The case of unbalanced supply presents a uniquely difficult problem in motor applications since its causes are varied. In many situations a static starter utilizing back-to-back thyristors in series with the motor lines is already installed for the purpose of soft starting or for power factor improvement. An attractive low-cost solution for phase unbalance is simply to modify the control strategy of the static starter by adjusting the firing angles of the three thyristors pairs independently. In this manner, the series connected thyristors serve the function of unsymmetrical, variable supply impedances which can be used to balance the voltage across the motor phases. A new digital controller utilizing a static starter for balancing the phase currents of an induction motor operating with unbalanced supply is presented. Experimental results show a marked reduction in the current unbalance from approximately 40% to a few percent and clearly demonstrate the attractiveness of the new phase balancer