Theory of a novel voltage-sustaining layer for power devices

The theory of a novel voltage-sustaining layer for power devices, called a Composite Buffer layer (CB-layer for short) is proposed. The CB-layer can be implemented in several ways, one particular implementation is used here, which consists of alternating n- and p-type regions, that are parallel to the direction of the applied electric field. In the off-state, the fields induced by the depletion charges of both region types compensate each other to allowing the doping in both n-regions and p-regions to be very high without causing a reduction of the breakdown voltage. In the onstate the heavy doping ensures the voltage drop is very low and that the saturation current density high. A simple relationship between the specific on-resistance and R_on and the sustaining voltage V_B can be shown to be R_on=2.53 × 10⁻⁷bV_B^1.23 ωcm², where the breadth b (in μm) of each region is much smaller than the thickness W. The design method of the CB-layer is discussed in some detail. The simulation results are shown to be in perfect agreement with the theory. The structure has application to a wide variety of different power devices. An RMOST structure has been used to demonstrate the benefits of the technique in the paper, for which excellent performance is demonstrated.     

Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

用于高压电容器的SrTiO3基陶瓷

报道ＳｒＴｉＯ３基陶瓷的制备方法和介电性质，给出了用此种陶瓷制成的高压电容器的试验结果，并对它位进行了讨论。     

航空油品高频/高压电脱水微观机理

设计并建立了一套高压电物理化学显微分析装置，为研究高压电物理化学领域的微观机理提供了一种新的技术途径。采用该技术，研究了胜利稠油经6％加氢裂解柴油稀释的原料油的高频／高压电脱水的微观机理。该原料的脱水率达96．7％，高于传统的电脱水方法。     

单稳态触发器的结构及其开关级设计原理

根据单稳态触发器定时单元特性,提出了单稳态触发器的一般结构.在此基础上,运用传输电压开关理论进行了CMOS单稳态触发器的开关级设计研究,并具体设计了两个单稳态触发器.设计实例表明文中提出的方法不仅简单、有效,而且具有通用性.     

镁法海绵钛生产工艺中大型无隔板镁电解槽的节能实践

以镁法海绵钛生产工艺中大型无隔板镁电解槽的实际节能情况为例，探讨了在镁电解生产中的非生产耗电、生产耗电、漏电等因素造成的能量浪费，阐述了生产中粗镁直流电耗、电流效率、工作电压3者之间的关系，指出了影响电解槽工作电压的有关因素及降低电解槽工作电压的途径。     

基于二阶矩阵微分方程的机械振动系统线性二次型调节器设计

本文讨论机械振动系统线性二次型状态调节器（LQR）问题，直接针对系统二阶运动微分方程，性能指标为一个依赖于二阶导数的泛函。由欧拉-拉格朗日方程得出一个系统矩阵增广的二阶线性微分方程，指出该方程稳定的特征对就是最优控制振动系统闭环特征对，并给出求解最优控制状态反馈矩阵的方法，另外，由本文方法还可得出基于速度和加速度反馈的最优控制反馈矩阵。这里不涉及求解代数矩阵Riccati方程。     

风电典型机型的闪变严重度分析

风力发电机组的并网运行对当地电网的电能质量有不良影响。为此．根据定速机型、变速机型引起电压波动和闪变的原理及并网风电机组电能质量的国际电工标准IEC61400—21，讨论了测量风电机组输出闪变的方法，给出了两种典型机型的短时闪变严重度与风速的关系实验曲线，并对不同风速段的闪变成因进行了分析。结果表明，变速风电机组在高风速区域综合应用桨叶节距角和变流器控制实现输出功率的稳定能够减小短时闪变严重度，在低风速区域追求最佳风能利用系数将使闪变严重度值增高。     

接地故障保护的设置和整定(三)

7 TT系统接地故障保护 TT系统的电源中性点直接接地,而电气设备的外露可导电部分则经各自的PE线接地。这样在大多数情况下,由于故障回路包括两个接地电阻,使接地故障电流太小,不足以使过电流保护动作切断接地故障电流。而且由于故障电流小,故障点未被熔焊,故障点阻抗是难以估计的接触电阻。因此,TT系统接地故障回路阻抗和故障电流难以估算。所以,必须设置漏电电流动作保护。     

Mg-doped LiNi0.5Mn1.5O4 spinel for cathode materials

Lithium-ion batteries are becoming more and more important not only for portable electronic devices, but also in prevision of high power electric vehicles. In such an optic, deep studies regarding all the components of a secondary battery are in development. In this study, high voltage cathode materials have been selected. Crystals with spinel structure have a 3D vacancy pathway suitable for Li-ions transport. The material under study was LiNi_0.5Mn_1.5O₄ doped with magnesium replacing the nickel. Various samples were synthesized via three different routes: a solid-state method, a modified sol–gel method and a xerogel method. The structure and morphology of the powders were analyzed with HRTEM and XRD. Electrochemical tests were also performed. A wide range of particle sizes (from micro to nanosize) was the result of the different synthesis routes. Unfortunately pure materials were not always obtained. The electrochemical tests showed improvement of the material's cyclability, by reducing the particle size. The electrochemical tests further confirmed the existence of a Li_1+dMn_2−dO₄ impurity. The results are quite promising, however, further improvement of the purity of the electrode composition are needed.