There are five parts are as follows : in part one , the concept of switching function is introduced first to establish the nonlinear mathematical model of the induction motor variable frequency speed adjustment system which is fed by a sine pulse width modulated ( spwm ) inverter and takes the effect of the main magnetic circuit saturation into consideration , then the low frequency oscillation of the system is simulated according to the model . next , from the view point of energy conversion of the inverter - induction system , a criterion for the low frequency oscillation is proposed to determine whether the system is in low frequency oscillation which is judged by whether the interval of the negative current component of the inverter input current is more than 1 / fc ( fc is the carrier wave frequency of the inverter ) or not 首先引入开关函数概念，建立了正弦脉宽调制( spwm )逆变器供电异步电动机，考虑主磁路饱和时的变频调速系统整体数学模型，模拟系统的低频振荡；其次从逆变器-异步电动机系统能量转换角度出发，提出通过检测逆变器输入电流中负电流的间隔时间是否大于1 / f _ c ( f _ c为逆变器载波频率)来判定系统是否出现低频振荡；最后的实验结果验证了系统低频振荡建模和判据的实用性和正确性。
Harmonic components of the input current in method 2 is lesser than method 1 , neglecting the losses and switching effects of the converter . the decreation of the harmonic components is not apparent , but different between method 2 and method 1 , due to the influence of switch losses of the igbt , which is consisted of two igbt and two frd 当仿真模型中的双向开关由两个igbt和两个快恢二极管组成时，由于igbt的开关损耗等因素对输入电流的影响，在仿真得到的输入电流频谱图中，谐波成分的减小不是很明显，但调制策略方式2和方式1的谐波成分仍有所不同。
Ppfc working principle , circular current and effects of clamping capacitor are studied in this paper in detail . because of the clamping capacitor , ppfc have some good features compared with ppc : reducing the fluctuate of the input current ; restraining the voltage spike of the power mosfet ; avoiding the bias - magnetic of the transformer 由于箝位电容的加入，相对于推挽电路而言，该拓扑具备了一些独特的优点：减小了输入电流的脉动：削弱了开关管的关断电压尖峰；有效抑制了变压器的偏磁。
Firstly , this paper proposes the mathematical model and finite - element analysis model of torque motor with mf and without mf . secondly , the electromagnetic field of torque motor is analyzed using the ansoft maxwell software ; static output torque of torque motor with mf and without mf is calculated . then the rotary angle of torque motor with different input electric current and mf is measured using three - coordinate measurement device 本文首先给出了添加磁流体和不添加磁流体的力矩马达磁路数学模型及有限元分析模型,其次,利用ansoft公司的maxwell电磁场分析软件进行了力矩马达的二维和三维磁场有限元分析,对添加磁流体和不添加磁流体的力矩马达静态输出力矩进行了计算,并采用三坐标位移测量仪对不同输入电流作用下、添加不同特性磁流体时力矩马达的转角进行了测量,从而对输出力矩特性进行了实验研究。
An improved high - resolution current - mode sorter is presented . its structure complexity is o ( n ) , which is crucial to the expansion of its size , and its dynamic range is large . only one clock signal and one reset signal are needed . no biasing signal is required . the operation point is constructed according to the input current , so it is self - adaptive , which is very important for an all - purpose component . in average value circuit , subtraction circuit , winner - take - all ( wta ) circuit and control circuit , it has good performance even at a large input current . this sorter has high precision , high resolution and low power , as has been proved via hspice simulation . it can be implemented in the standard digital cmos technology and widely used in many fields , so it is of great value in applications 提出了一种改进的高精度电流型排序电路.它的结构复杂性仅为o ( n ) ,便于扩展;动态范围大;它是自适应的,工作点由输入电流确定,故不需要偏置信号,这对作为通用器件使用的排序电路来说是很重要的.通过利用平均值电路、减法电路、 wta电路和控制电路,可以使该电路在大输入电流下依然保持高性能. hspice模拟表明该电路具有高准确性、高精度、低功耗的特点.它能用标准数字cmos工艺来实现,可以被应用于很多领域,具有很高的应用价值
Three phase ac reactive power display control instrument ; single screen digital display ; outline dimension 16080mm ; no communication interface ; no transmit output ; three - phase four - wire system connection mode , high limit alarm low limit alarm ; switch power supply ; input voltage 0380v ; input current 05a , display reactive power 0114 . 0k var 三相交流无功功率显示控制仪:单屏数字显示外形尺寸16080无通讯接口无变送输出三相四线制接线方式，上限报警下限报警开关电源供电输入电压0 380v ，输入电流0 5a ，显示无功功率0 114 . 0kvar ,
Matrix converter ( mc ) is a power converter based on ac - ac direct conversion . more and more attention is paid to mc depending on its adventages , such as omitting the dc part , obtaining unit power factor , getting sinusoidal input currents and output voltages and easy to realize bidirectional flow of energy 矩阵变换器作为交交直接变换的功率变换器,以其无中间直流环节、具有单位输入功率因数和良好的正弦输入电流、易于实现能量双向流动等优点受到了国内外学者的广泛关注。
Chaotic switching signal obtained from chua ' s circuit was used to control buck dc / dc converter . by compared the power spectrum of input current between chaotic modulations and classical pwm , it demonstrate that chaotic switching modulations have good effect on spreading power spectrum , which can be used to reduce the level of emi and to improve emc of smps 通过对四种混沌调制模式下变换器输入电流与周期pwm模式下输入电流频谱的分析比较表明，混沌调制技术在扩展频谱方面有良好的效果，可以用于降低开关模式电源的电磁干扰( emi )水平，改善电磁兼容性( emc ) 。
With the serious problem of harmonics pollution to the power system , as well as the need of high performance of ac drive application , three - phase pwm rectifiers have been as active research topic in power electronics recently , due to the virtues , such as sinusoidal input currents , unity power factor , steady output voltage , good dynamics and bin - directional energy flow 随着电网谐波污染问题日益严重和人们对高性能电力传动技术的需要， pwm整流技术引起人们越来越多的注意。三相pwm整流器可以做到输入电流正弦、单位功率因数、直流电压输出稳定，具有良好的动态性能并可实现能量的双向流动。因此， pwm整流器成为当前电力电子领域研究的热点课题之一。
