电压波形对介质阻挡等离子体放电特性和体积力的影响

驱动电压波形对于介质阻挡放电等离子体激励器的放电状态和激励性能均有影响。基于典型构型的介质阻挡放电等离子体激励器(DBDPA)在静止大气中的放电实验,通过电学测量和电子天平测力,分别获得了不同驱动电压波形下DBDPA的放电电流–电压信号和射流产生的时均反推力等物理量。驱动电压波形主要包括正弦波、方波、对称三角波和正、负斜波。基于伏安特性图分析了放电电流、微放电电流脉冲等特性,基于Lissajous图分析获得了放电功率,初步讨论了沉积电荷对DBDPA起始放电的影响。结果表明:驱动电压波形所决定的电压变化率直接影响激励器的回路电流和等离子体微放电电流脉冲形态。放电中的表面沉积电荷形成虚拟电极,其在裸露电极极性发生反转时加强了电极间的电场,降低了起始放电电压阈值,使得放电得以提前。所有驱动电压波形中,方波驱动电压产生的时均反推力和放电功率均相对较大,正弦波次之,其余波形相对最小。其中,50%占空比方波产生的2个量最大。     

驱动电压对向列型液晶调制相位的影响

液晶作为空间光调制器控制系统的核心器件,其向相位调制特性能对液晶器件的驱动设计、特性的分析具有重大作用。根据液晶弹性体理论和动力学方程,通过差分法迭代法计算出外加电压下液晶分子指向矢随位置变化的分布。根据液晶分子指向矢的分布情况和液晶的电控双折射效应,得到向列型液晶调制相位随驱动电压变化关系。仿真得出,在液晶的驱动电压从0~5 V的过程中,液晶指向矢可以实现0~4π的调制相位变化。实验结果证明,随着驱动电极电压的变化,液晶0~4π的相位调制,实现了对液晶相位调制相位的测量。     

简述TFT液晶显示屏常用的极性变换方式与显示屏驱动电路

1.极性变换方式因为液晶分子的驱动电压不能固定在某一个值不变,否则,时间久了,液晶分子会发生极化现象,从而逐渐失去旋光特性。因此,为了避免液晶分子的特性遭到破坏,液晶分子的驱动电压必须进行极性变换,这就需要将液晶显示屏内的显示电压分成两种极性:一个是正极性;另一个是负极性。当显示电极的电压高于common(公共电极)电极电压时,就称为正极性;当显示电极的电压低于common电极电压时,就称为负极性。     

纳秒电脉冲对肝脏组织不可逆电穿孔消融区分布的时域有限差分法仿真

纳秒电脉冲消融是一种新型的电外科手术技术,在肿瘤切除中可以无创或少创器官旁组织,尤其是血管,达到既切除肿瘤,又不伤及周边组织的目的.纳秒电脉冲参数,如脉冲电压、脉冲持续时间、脉冲数、脉冲率等的选择是术前治疗计划设计的关键,术前进行仿真研究对手术设计至关重要.以人体模型Duke为对象,采用人体生物电磁仿真软件平台Sim4Life中的时域有限差分法(FDTD),对电脉冲波形、脉冲电压和电极间距在肝组织中的电场、能量密度、消融区域进行仿真.结果显示,在肝组织及旁组织中,电极中心电场强度较高,周边较低;脉冲波型对肝组织中电场和能量密度分布没有显著改变;消融区域包裹着电极;脉冲波型对消融区域没有变化,但脉冲电压和电极间距对消融区域有很大影响.因此,FDTD可以术前对电脉冲治疗计划设计,脉冲电压和电极间距两个参数是主要设计参数,Sim4Life是治疗计划设计的良好平台.     

TCL王牌等离子(PDP)4226H/42U3H型彩电驱动电路分析(二)

<正>2.驱动脉冲波形本机3个过程的驱动脉冲波形,如图2所示。(1)复位期它是一个子场开始的准备期,为寻址期的操作提供合适的条件。它主要包括一个斜沿上升期和一个斜沿下降期。斜沿上升期在Y电极以2.5V/μs的斜率逐渐增加电压到     

螺旋针-环结构等离子体射流放电过程分析

为降低气体的击穿和维持电压,设计一种螺旋针-环电极结构的等离子体射流装置,研究不同电压下的放电电压、电流波形。研究表明,氦气等离子体射流放电可以分为电晕放电、介质阻挡放电和射流放电三个阶段,并且可以通过放电电压、电流波形的特征进行区分。分析可知,射流管管径较大时,采用螺旋针状内电极结构可以减小电极间的平均气体间隙距离,从而降低气体的击穿和维持电压,使放电更加容易进行;电压反向过程中残留电荷使得合成电场得到加强,气体将"提前"发生放电;由于电极结构的不对称,气体在正半周期更容易发生放电,放电产生的电流脉冲数目更多,电流值更大;随着外加电压增大至14k V,放电最终过渡到丝状放电状态。     

脉冲电源驱动多针—平板电极介质阻挡放电影响因素研究

笔者采用μs振荡脉冲电源驱动多针—平板电极,产生空气中介质阻挡放电(DBD),测量了不同条件下放电的电压电流波形,拍摄了放电发光图像,并进一步计算得到放电功率和传输电荷量等主要放电参量,研究了多针电极密度、外加电压幅值和气隙距离对多针—平板电极DBD放电特性和放电参量的影响,并结合放电机理对所得到的实验结果进行了分析....     

同轴电极脉冲电晕放电形态的研究

通过理论推导得到脉冲电晕放电等离子体的电子平均能量 (用电子温度表示 )与同轴电极系统中的击穿电压有成正比的关系。实验研究了同轴电极系统中脉冲电晕等离子体中脉冲波形参数 (脉宽和上升时间 )对电极击穿电压峰值 (电子平均能量 )的影响 ,结果表明 ,减短脉冲宽度和减少脉冲上升时间可提高反应器的击穿电压并增加激发电子的能量。     

脉冲电压下聚酰亚胺空间电荷行为及其机理研究

电力电子装备长期处于高重复频率、陡上升时间脉冲电压运行工况,绝缘更容易发生劣化和早期失效。为探究脉冲电压下绝缘失效的微观机理,对ns级别下的脉冲边沿前后空间电荷分布情况进行研究对比,探究了电场强度、硅油对脉冲边沿时刻电荷振动波形的影响。通过分析不同脉冲上升时间下的电荷振动波形及电压波形频谱、电荷积聚特性,阐明了脉冲电压边沿时刻电荷振动机理以及ns脉冲下电荷行为对绝缘劣化影响机理。研究发现,ns脉冲上升沿和下降沿前后电荷分布特性存在差异,在脉冲边沿处发现了特殊的空间电荷迁移行为;电场强度会影响异极性电荷的积累速度及积累量,从而影响电荷振动波形的形状;电极与试样之间涂敷硅油会影响电荷振动波形的极性;5×106～1×107 Hz频段的电压分量对空间电荷振动起主要作用;ns脉冲电压下电荷积聚导致电场畸变更加严重。     

一种基于LabVIEW控制的电压尖峰发生器

为实现对机载用电设备进行电压尖峰干扰测试,本文研制了一台符合RTCA-D0160E、GJB181-1986标准的电压尖峰发生器.本文采用全桥逆变电路结合LC谐振实现电压尖峰输出,推导了电路中主要元器件参数与电压尖峰的函数关系,并给出了主电路中脉冲变压器的设计方法.本文阐述了LabVIEW产生驱动信号控制电压尖峰发生器的原理与方法,并设计了驱动逻辑.实验波形验证了分析设计的正确性,完全符合RTCA-DO160E与GJB181-1986对电压尖峰波形的各项规定.     

Analysis of PWM GTO Current Source Inverter-Fed Induction Motor Drive System

A GTO current source inverter which consists of six main GTO's, two auxiliary GTO's, and three capacitors is presented. This inverter can supply both the sinusoidal voltage and current to the motor by pulsewidth modulation (PWM) techniques. The normal PWM pattern produced by two control signals with the carrier and the modulating waves and the optimal PWM pattern determined by the harmonic analysis are described. The experimental waveforms for 2.2-kW induction motor drives are given and the circuit operation of this inverter in the PWM technique is clearly shown. In addition, the steady-state characteristics of this inverter-induction motor drive system are analyzed by the state-variable methods, and a close agreement between the analyzed and the experimental waveforms is obtained. It is shown that the harmonic components are eliminated or reduced by using the optimal PWM pattern, and the new inverter with sinusoidal current and voltage is very excellent for ac motor drive.     

超声波电机谐振驱动电路仿真与实验研究

根据超声波电机的容性负载特性,通过串联匹配电感,构成由超声波电机本体参与的LC谐振升压的无变压器式驱动电路。文章提出了固定所有电路参数,只改变驱动信号频率、占空比和谐振周波数的方法,实现对超声波电机的驱动控制。以USR30为研究对象,对此方法进行实验验证,并为进一步有效地驱动控制电机提供可靠的依据。     

Improved Torque and Flux Performance of Type-2 Fuzzy-based Direct Torque Control Induction Motor Using Space Vector Pulse-width Modulation

The conventional proportional integral controlled direct torque control of an induction motor using the space vector pulse-width modulation technique may provide satisfactory dynamic response. However, the proportional integral controller (PIC) does not provide efficient dynamic performance in the induction motor drive during sudden changes in the load or speed. To improve dynamic performance of the induction motor drive, the PICs are replaced by type-2 fuzzy logic control. The type-2 fuzzy improves the starting transient performance as well as the steady-state response. In addition, the type-2 fuzzy direct torque control provides lesser current total harmonic distortion, flux distortion, and torque pulsation of the induction motor drive compared to conventional direct torque control. A MATLAB Simulink (The MathWorks, Natick, Massachusetts, USA) model for direct torque control with type-2 fuzzy logic control is developed to simulate the response of an induction motor drive with different operating conditions. The space vector pulse-width modulation technique is used to drive the inverter, as it produces lesser total harmonic distortion in inverter current and voltage waveforms for a given switching transition due to the single switching frequency for the movement of each state vector. A prototype type-2 fuzzy-based direct torque control induction motor with space vector pulse-width modulation is developed to validate the simulated response. The control signals for the inverter are generated by the DSPACE DS1104 (DSPACE GmbH, Germany) to drive a two-HP induction machine.     

A Novel Power Factor Correction System Based on Sliding Mode Fuzzy Control

In this study, a novel Power Factor Correction System based on Sliding Mode Fuzzy Control is presented. This structure is used as an AC/DC/AC drive system for asynchronous machine. Non-sinusoidal source current of the system is improved to a sinusoidal waveform by the novel Power Factor Correction System controlled by Sliding Mode Fuzzy Controller. Sliding mode control technique (variable structure control) is preferred because of its robustness. Additionally, fuzzy control algorithm is adapted to Sliding Mode Control for eliminating or reducing chattering problem. A DC–DC boost converter is used to provide DC-link voltage to the inverter Three-phase voltages for Space Vector Pulse Width Modulation technique are represented by a voltage space vector in α-β space using the Clarke transformation for two-level voltage source inverter. The harmonic performance of the AC/DC/AC drive system, source side and load side current waveforms, and total harmonic distortion (THD) values are given in figures. Experimental results show the significant improvement in source current with eliminated harmonics and increased power factor from 0.63 to 0.998 value.     

Computer simulation of electric motor drive systems including thepower electronic network

A method for studying a combined power electronic network/variable-speed AC electric motor drive system based on a simple numerical algorithm is presented. It can be applied to any machine that can be describing using a d-q-type model. An LCI-fed synchronous motor drive in the steady state is used as an illustrative example. A simple iterative technique is used to find the initial conditions in the time domain, making use of an infinite link inductance approximation to provide the first iteration. The predicted waveforms of voltage and current for a sample operating point are compared with their experimental equivalents (measured on a 3 kVA prototype drive system), and a good level of agreement is reached. The technique is sufficiently simple to have been implemented on a personal computer     

A steady state solver for modelling rotating electromechanical devices exploiting the transformation from time to position domain

The paper presents a study on a novel steady state solver for modelling rotating electromechanical devices. As the new contribution, the transformation of the system from time to position domain is exploited to improve the efficiency of computation. The proposed methodology is well suited to optimizing the current or voltage waveforms to drive the system with an imposed reference torque. To illustrate the technique, a brushless direct current motor is considered. Copyright © 2013 John Wiley & Sons, Ltd.     

Excitation of Variable-Reluctance Motor Drives

ABSTRACT

This paper focuses on two major issues which need careful consideration when designing an excitation for variable-reluctance motor (VRM( drives. The drive is comprised of a VRM, an inverter and an excitation and control strategy. The controller acts to enforce the excitation. The specific issues addressed here include the modeling of the drive and selecting a topology Toe the drive. These issues were found to be important during the design of an optimal-efficiency excitation for a high-power (60 kW( VRM drive. The drive used for the running example was designed for electric vehicle propulsion using a bifilar wound VRM.

The importance of drive modeling is examined through an example. The example uses two magnetic models for the same VRM to generate current waveforms for drive operation at a specific speed. The attributes of the current waveforms are then compared and their influence on excitation design is discussed. The comparison shows that meaningful excitation design requires accurate models of drive operation. The implications of the magnetic model on the design of the VRM are discussed.

With regard to inverter topology, a detailed efficiency comparison between a bifilar and a monofilar high-power VRM drive is presented. Each drive is comprised of a motor with identical geometries and the same number of turns per pole, a switching inverter, an excitation strategy and a control algorithm. After examining drive efficiency at several operating points over the intended duty, the paper concludes that the monofilar drive offers increased efficiency over the bifilar drive.     

两相不对称交流感应电机矢量控制的仿真研究

运用MATLAB/SIMULINK工具建立了两相不对称交流感应电机矢量控制调速系统的仿真模型;介绍了两相不对称电机矢量控制的基本原理和两相三桥臂逆变器的SVPWM工作原理。对两相不对称电机矢量控制调速系统进行仿真研究,给出了电机矢量控制调速的仿真实验波形。     

Nonsinusoidal electrical measurement accuracy in adjustable-speedmotors and drives

Accurate measurements of voltage, current and power under nonsinusoidal conditions are essential for determining the efficiency of a drive system and performing separation of losses between an adjustable-speed drive (ASD) and an electric motor. That information is invaluable for equipment designers, manufacturers and users. Three modern power meters and analyzers were tested to determine their accuracy with various nonsinusoidal waveforms applied. The meters were subjected to waveforms that are characteristic to the three most common fractional and integral horsepower ASD technologies, namely, pulsewidth modulation induction, brushless DC and switched-reluctance drives. The tests were performed under field conditions and in a computer-controlled laboratory environment. The obtained results show that some meters are able to measure accurately electric power at the input to ASDs. However, the output power of ASDs for brushless DC and switched-reluctance technology was not measured with acceptable accuracy by any of the tested meters. Possible reasons of meters inaccuracies and suggestions for performance improvement are presented. Conclusions on the present state of ASD electric power measurements and recommendations for further research are given     

高频脉冲电源的研制

针对电磁超声实验对脉冲电源的需求,研制了一种高频脉冲电源。采用UCC2895作为信号源,利用全桥电路将信号功率放大。详细介绍了信号发生电路、驱动电路和全桥逆变电路的设计方法,并给出了各主要节点的实验波形。该电源达到了各项技术要求,已成功应用于电磁超声实验。