具有多分界面的非线性电路中的非光滑分岔

本文分析了具有多分界面的非线性电路在不同时间尺度下的快慢动力学行为. 在一定的参数条件下,系统的周期解为簇发解,表现出明显的快慢效应. 根据状态变量变化的快慢,把全系统划分为快子系统和慢子系统两组. 根据快慢分析法将慢变量看作快子系统的控制参数,分析了快子系统的平衡点在向量场不同区域内的稳定性. 非光滑系统的分岔与向量场的分界面密切相关,对于具有快慢效应的两时间尺度非光滑系统,快子系统的分岔则取决于分界面两侧平衡点的性质. 通过在临界面引入广义Jacobi矩阵,讨论了快子系统非光滑分岔的类型,即多次穿越分 关键词： 非线性电路 多分界面 非光滑分岔 快慢效应     

切换电路系统的振荡行为及其非光滑分岔机理

探讨了周期时间开关及控制阈值下在两个Rayleigh型子系统之间切换的电路系统随参数变化的复杂动力学演化过程, 通过对子系统平衡点的分析, 给出了参数空间中Fold分岔和Hopf分岔的条件, 考察了切换面处广义Jacobian矩阵特征值随辅助参数变化的分布情况, 得到了切换面处系统可能存在的各种分岔行为, 进而讨论了系统不同行为的产生机理, 指出系统的相轨迹存在分别由周期开关和控制阈值决定的两类不同的分界点, 而系统轨迹与非光滑分界面的多次碰撞将导致系统由周期倍化分岔导致混沌振荡.     

基于人工过零的失超保护100 kA真空断路器试验北大核心CSCD

在超导磁体电源系统中,失超保护系统具有重要的地位,能够将磁体能量迅速转移并消耗。聚变堆主机关键系统综合研究设施项目对失超保护系统提出了100 kA直流分断的技术要求,其中采用真空断路器作为转移支路开关。针对CRAFT失超保护系统,设计了串联结构的100 kA直流真空断路器并完成了样机制造。通过现场试验,在人工过零电路的配合下,所设计和制造的真空断路器完成了100 kA直流分断测试。     

Investigation on arc characteristics in cup-shaped contacts with different structure for transverse magnetic field vacuum circuit breaker

The cup-shaped transverse magnetic field (TMF) contacts contain radial components and tangential components in the TMF generated when the current is interrupted. The tangential force generated by the radial magnetic field component drives the vacuum arc to rotate, and the tangential magnetic field component generates a radial force that causes the vacuum arc to move radially outward. In this paper, in order to study the influence of the arc force direction on the arc characteristics, the influence of the contact structure parameters such as the inclination of the inner wall on the arc force direction is simulated, and the breaking tests of different levels of current are carried out on the contact with different structure parameters. It is found that the direction of the Lorentz force has a significant effect on the breaking characteristics of the current, and the tangential and radial force components have varying degrees of influence on the motion characteristics of the arc during the start process and the metal droplet splashing.     

激光电源脉冲功率切换电路仿真分析

激光电源脉冲功率切换电路稳定工作是电源可靠性的保证。电路参数选取直接影响晶闸管、二极管的工况,而晶闸管的良好工况是保证切换激光电源长期可靠运行的基本条件。基于PSCAD软件建立切换电路的仿真模型,重点仿真分析了阻容电路参数配置、限流电阻、并联晶闸管触发同步性对晶闸管和二极管的影响。仿真结果表明,电流上升率过大是晶闸管门极损坏的原因,关断支路中的反向过压是二极管损坏的原因。并针对实际电路,提出晶闸管二极管保护的优化配置方案。     

激光电源脉冲功率切换电路仿真分析

激光电源脉冲功率切换电路稳定工作是电源可靠性的保证。电路参数选取直接影响晶闸管、二极管的工况,而晶闸管的良好工况是保证切换激光电源长期可靠运行的基本条件。基于PSCAD软件建立切换电路的仿真模型,重点仿真分析了阻容电路参数配置、限流电阻、并联晶闸管触发同步性对晶闸管和二极管的影响。仿真结果表明,电流上升率过大是晶闸管门极损坏的原因,关断支路中的反向过压是二极管损坏的原因。并针对实际电路,提出晶闸管二极管保护的优化配置方案。     

基于RBF网络的断路器电流自适应保护研究

针对传统断路器电流保护方法存在受系统运行方式影响、整定困难、智能化低等问题,本文提出了基于RBF的断路器电流自适应保护算法,并给出了算法的模型。该算法融合了RBF神经网络的故障检测和电流自适应保护。首先通过RBF网络检测负载线路的电流故障,然后用电流自适应算法进行保护。在对神经网络进行训练时,利用PSO算法对RBF神经网络的参数进行优化以此来提高网络的泛化能力和学习能力;然后采用优化后的PSO-RBF神经网络对电流故障进行诊断。实验表明,该算法较大地提高了断路器智能化管理水平。     

非线性切换系统的动力学行为分析

建立了周期切换下的非线性电路模型,基于子系统平衡点及其稳定性分析,分别给出了其相应的fold分岔和Hopf分岔条件,讨论了子系统在不同平衡态下由周期切换导致的各种复杂行为,指出切换系统的周期解随参数的变化存在着倍周期分岔和鞍结分岔两种失稳情形,并相应地导致不同的混沌振荡,进而结合系统轨迹及其相应的分岔分析,揭示了各种振荡模式的动力学机理. 关键词： 周期切换 倍周期分岔 鞍结分岔 混沌     

Full wave analysis of non-radiative dielectric waveguide modulator for the determination of electrical equivalent circuit

This paper reports the determination of electrical equivalent circuit of ON/OFF modulator in non-radiative dielectric (NRD) guide configurations at Ka-band. Schottky barrier mixer diode is used to realize this modulator and its characteristics are determined experimentally using vector network analyzer. Full wave FEM simulator HFSS is used to determine an equivalent circuit for the mounted diode and modulator in ON and OFF states. This equivalent circuit is used to qualitatively explain the experimental characteristics of modulator.      

Nonlinear dynamics in an electrical circuit containing a ferroelectric

Nonlinear effects in a series oscillator circuit containing a ferroelectric capacitor are investigated as a function of the temperature and the amplitude of the applied field. A relation is established between the circuit parameters and the resonance shift in samples of a pure triglycine sulfate crystal and in samples containing chromium impurity ions. The observed effects are explained on the basis of a feature in the domain structure of the samples and the influence of point defects on it. Fiz. Tverd. Tela (St. Petersburg) 39, 918–919 (May 1997)     

Measurement of ion parameters during a forced switching off ofcurrent in vacuum

This paper presents the results of ion parameters measured during a forced current commutation of a diffuse vacuum arc, aimed at evaluating the role of ions in discharges occurring rarely after the counterpulse commutation process, in a contact arrangement corresponding to a low-voltage vacuum switch. A sinusoidal half-wave current was interrupted near its amplitude of 400 A with a counterpulse of rise velocities 2.4 and 32 A/μs. In this way, a forced switching off of dc current was modeled. A retarding field analyzer was used for ion parameter measurements at the forced commutation process. Ion potentials up to 100 V were measured at the current zero moment, and the average decay times of ions after current zero were in the range from a few microseconds up to 30 μs as a function of observed ion potential. The measured values of decay times show the rather negligible role of ions in the discharge process after the counterpulse commutation in the examined contact arrangement. The rise time of the countercurrent is proposed as a factor in the successful forced current commutation under these conditions, and values up to a few amperes per microsecond of countercurrent rise velocity can be considered as the limit value     

Laser terahertz-emission microscope for inspecting electrical faults in integrated circuits

A laser terahertz-emission microscope (LTEM) system is proposed and developed for inspecting electrical faults in integrated circuits (IC). We test a commercial operational amplifier while the system is operating. Two-dimensional terahertz-emission images of the IC chip are clearly observed while the chip is scanned with a femtosecond laser. When one of the interconnection lines is cut, the damaged chip has a LTEM image different from that of normal chips. The results indicate that the LTEM system is a potential tool for IC inspection.     

荷控忆阻器等效电路分析模型及其电路特性研究

忆阻器是物理上新实现的具有记忆特性的基本二端电路元件. 根据φ-q关系式的泰勒级数形式构建了荷控忆阻器等效电路分析模型, 以三次非线性荷控忆阻器模型为例, 对不同参数条件下的荷控忆阻器进行了伏安关系、有无源性等电路特性的理论分析. 结果表明: 荷控忆阻器的伏安关系具有斜体“8”字形紧磁滞回线特性, 随其参数符号的不同, 荷控忆阻器呈现出无源性和有源性, 导致其电路特性发生相应的变化; 相比无源荷控忆阻器, 有源荷控忆阻器更适用于作为二次谐波信号产生电路使用. 制作了荷控忆阻器特性分析等效电路的实验电路, 实验测量结果很好地验证了理论分析结果. 关键词： 荷控忆阻器 等效电路 伏安关系 电路特性     

SF_6断路器气体压力表智能遥视研究

以压力表盘图像为对象,通过一种改进的Otsu阈值分割算法,在离差平方和约束条件基础上区分整体阈值,确定适应度函数,以选取最佳阈值,可避免因单一法排除边缘和噪声区域而遗漏部分目标和背景像素;Hough变换通过直线提取法确定指针与圆提取法定圆取圆心相结合,依据表盘指针经圆心原理较准确定位指针位置,保证了表盘指针识别和数值读取精确度。实验结果表明该智能遥视系统能够实时监测SF_6断路器表盘气压值,给出的改进Otsu阈值分割算法能较准确分割目标区域,基于角度识别指针数值方法读取误差保持在3%范围内。     

一个跃变电路切换系统的振荡行为及分岔机理分析

本文研究两个非线性电路系统通过开关组成的时间切换系统的复杂振荡行为及其产生机理.利用开环运算放大器放大倍数为极大值的特性,即运算放大器总是处于正的或负的饱和状态,当输入电压从负过零变正时,输出电压从正饱和状态跃变为负饱和状态,本文选择子电路系统中的非线性部分为跃变函数.首先对两个子系统进行了稳定性分析,给出了不同参数条件下的振荡行为,然后在子系统单个参数在一定范围内变化,而其他参数保持不变的情况下,研究了切换系统的复杂振荡特征,并分析了其产生机理.由于子系统方程的非光滑性和切换带来的整个系统的非光滑性,使得整个系统的周期振荡轨迹有四个切换点,随着参数的变化,周期振荡轨线与非光滑分界面发生擦边分岔,导致周期振荡分裂成两个对称的周期振荡.并且研究了切换点位置改变对整个系统周期振荡行为的影响以及切换点处的分岔机理.     

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

When the contacts of a medium-voltage DC air circuit breaker(DCCB) are separated, the energy distribution of the arc is determined by the formation process of the near-electrode sheath. Therefore, the voltage drop through the near-electrode sheath is an important means to build up the arc voltage, which directly determines the current-limiting performance of the DCCB. A numerical model to describe the near-electrode sheath formation process can provide insight into the physical mechanism of the ...     

Characteristics of a vacuum switching contact based on bipolaraxial magnetic field

Axial magnetic field (AMF) contacts can increase the interruption capability of vacuum interrupters. Depending on the design, the principles of the local axial field arrangement are different. For unipolar arrangements the direction of the axial magnetic field is the same within the whole contact area. For bipolar arrangements, the polarity of the field changes once. In this paper investigations have been carried out to characterize a bipolar AMF contact system and to test its interruption performance. The influence of the bipolar AMF on the arc development and the thermal stress is described by high speed camera and contact surface pictures. In addition, three-dimensional AMF simulations have been performed by means of a finite-element program to estimate the influence of slots within the contact plates on the AMF performance. The high interruption capability of the bipolar AMF contact system has been verified in different test laboratories up to 12 kV/80 kA_RMS (symmetrical) and 36 kV/40 kA_RMS (including 40% DC) by three and single phase tests. The investigations are completed by measuring the post-arc current and the shield-potential during recovery period, both describing the switching behavior of the contact system     

真空及空气中金属丝电爆炸特性研究

开展了铝丝在真空和空气环境中的电爆炸特性研究.从金属丝电爆炸的电压、电流波形得到了金属丝内的沉积能量,并基于以上电参数特征分析了电爆炸产物的状态,获得了空气中铝丝电爆炸电流暂停时间随初级储能电容充电电压的变化规律.真空和空气中铝丝电爆炸在电压击穿时刻的沉积能量分别为2.8和6 eV/atom.采用波长为532 nm、亚纳秒激光探针对金属丝电爆炸物理过程开展了高时空分辨率的阴影和纹影诊断.阴影图像清晰地展示了不同气氛环境中高密度电爆炸产物的膨胀过程,根据光学诊断图像分析了高密度丝核沉积能量的结构和空气中铝丝电爆炸产生的激波的膨胀轨迹.真空和空气环境中高密度电爆炸产物的平均膨胀速度分别为1.9和3 km/s.基于实验数据和输运参数模型,估算了金属丝在电压击穿时刻的温度.     

介观RLC电路在热真空态下的量子涨落

利用热场动力学的方法研究了介观RLC电路在具有热噪声的真空态下电荷和磁通(电流)的量子涨落.从而得到了有限温度下这一电路在热真空态下的量子涨落与温度的关系.结果表明,介观RLC电路的量子涨落不仅与电路中的元件参量和电路的共振频率ω有关,而且与温度T有关.温度越高,介观RLC电路的量子噪声越大 关键词： 介观RLC电路 热真空态 量子涨落