三峡水轮发电机绕组端部绝缘固定系统的特点

本文介绍了哈电生产三峡电厂水轮发电机绕组端部绝缘固定系统.其特点是:结构简单可靠、工艺操作方便,具有一定的先进性.     

贵州光照水电站圆筒阀控制系统

光照水电站圆筒阀控制系统是由哈尔滨电机厂有限责任公司提供.圆筒阀是新兴的一种水轮机进水阀门,作为水轮机的一部分,有着广泛应用的前景.特别在泥沙多的流域,圆筒阀在实际使用过程中优势更明显.本文着重介绍贵州光照水电站圆筒阀控制系统、结构、功能和运行工况.     

采用滞环调节的直接转矩控制系统新型建模研究

从直接转矩控制(DTC)的基本原理出发,提出了一种适合于全速范围的新型系统仿真模型.针对传动系统开关器件的开关频率对大中功率感应电动机高速域DTC控制的约束,设计了一种基于施密特触发器的变容差磁链滞环调节器,以实现高低速时多边形磁链轨迹和近似圆形磁链轨迹的平滑切换.仿真结果表明了该模型的有效性,能保证系统的控制品质,具有工程实用价值.     

1.5MV高压发生器的工艺改进和仿真计算

为了使应用于火电厂脱硫脱硝的大功率电子加速器高压发生器能稳定运行,介绍了电子加速器的结构和高压发生器的特点,并针对高压发生器经常发生打火造成高压硅堆和跳线损坏的问题,提出和实施了以下改进措施:通过改变高压电极的设计结构改善高压电极附近电场强度的分布;增加高压硅堆管芯数量及减小高压硅堆环氧浇注层厚度。有限元仿真和高压实验的结果表明,电压的不均匀降落和高压硅堆的工艺是影响高压发生器稳定性和可靠性的原因。实施改进方案后,明显提高了高压发生器的击穿电压且达到了其设计指标,大大提高了高压发生器运行的稳定性和可靠性。     

Visual quality with corneo-scleral contact lenses after intracorneal ring segment (ICRS) implantation for keratoconus management

PurposeTo evaluate the visual quality results when fitting a corneo-scleral contact lens (CScL) after intracorneal ring segment (ICRS) implantation for keratoconus management.MethodsTwenty-seven eyes of 27 patients with keratoconus underwent ICRS implantation and had CScL fitted as their visual quality was unsatisfactory with their spectacles or contact lenses. Patients received a complete eye examination, refraction and visual acuity assessment, anterior eye biomicroscopy, ocular fundus examination, corneal topographic analysis, endothelial-cell count, and visual quality assessment using contrast sensitivity and aberrometry tests. A diagnostic trial set was used in the fitting process, and patients were assessed according to a standardised methodology, including subjective visual quality and comfort, and contact lens usage time. The follow-up period was one year.ResultsAfter fitting CScL, log-MAR visual acuity values improved significantly in relation to the best spectacle-corrected vision (0.22 ± 0.17 vs 0.00 ± 0.12; p < 0.001). Total high-order aberrations decreased 33% (2.62 ± 1.31 vs 1.75 ± 1.81 μm; p < 0.009) and the spatial frequencies of contrast sensitivity all improved (all p < 0.05). Furthermore, 70.37% of patients reported high ratings of subjective visual quality (favourable and very favourable) and prolonged usage times (11.78 ± 3.93 h). After wearing CScL for one year, no adverse ocular effects or clinically relevant changes in corneal parameters, visual quality, comfort ratings or usage time were found.ConclusionThis CScL appears to be an alternative reasonable option for keratoconic eyes with ICRS placement, providing an improvement in subjective visual quality.     

一种X射线环焊缝图像质量评价方法

为了缩小增强后环焊缝图像质量主客观评价的差距,提出了一种基于人眼视觉的无参考质量评价指标。通过分析人眼的视觉特性,建立图像模糊评价模型,设定主观评价方法;主客观评价值进行曲线拟合,经验证,评价结果与主观评价结果具有线性拟合关系,评价结果接近人眼最佳视觉,验证了评价指标的可行性。     

基于RCM 的导弹装备最佳预防性维修周期决策

针对目前确定预防性维修周期时存在不确定性的问题,建立了基于RCM的导弹装备维修周期决策模型。分别以总费用最小和可用度最大为目标建立导弹装备维修周期决策模型,采用蒙特卡罗仿真进行模型求解,采用模糊决策方法确定多目标综合最佳预防性维修周期,并以某型导弹装备密封圈为例,验证方法的有效性。实践分析结果表明:该方法综合权衡了费用和可用度因素,能较好地解决可用度低下且维修费用居高不下的问题,有一定应用和参考价值。     

一种新的抗总剂量辐射加固P沟道VDMOS终端结构

Using positive surface charge instead of traditional γ-ray total dose irradiation, the electric field distribution of a P-channel VDMOS terminal has been analyzed. A novel terminal structure for improving the total dose irradiation hardened of P-channel VDMOS has been proposed, and the structure is simulated and demonstrated with a -150 V P-channel VDMOS. The results show that the peak current density is reduced from 5.51 × 10^3 A/cm^2 to 2.01 × 10^3 A/cm^2, and the changed value of the breakdown voltage is 2.5 V at 500 krad（Si）. Especially, using 60Co and X-ray to validate the results, which strictly match with the simulated values, there is not any added mask or process to fabricate the novel structure, of which the process is compatible with common P-channel VDMOS processes. The novel terminal structure can be widely used in total irradiation hardened P-channel VDMOS design and fabrication, which holds a great potential application in the space irradiation environment.     

一种应用于平方公里中频阵的八角环天线阵

结合平方公里中频孔径阵列的应用场景,文中提出了一种基于电阻膜频率选择表面的超宽带八角环天线单元。其通过在八角环天线阵列与接地板之间加载方环形电阻膜频率选择表面,对由金属地板在对应频点因反相叠加而产生的驻波峰值有效抑制,进而拓宽了天线带宽以及降低了天线剖面。仿真结果表明:加载电阻膜频率选择表面后,天线阵元最终在±45°扫描范围内获得了5:1的阻抗匹配带宽,且天线的剖面降低了约27%。此外,在整个工作频带内天线阵元具有稳定的有源方向图、较宽的半功率波瓣宽度以及较好的极化性能。     

影响绝缘子雷电冲击特性的因素分析

结合线路运行中绝缘子雷击故障的特点,对绝缘子悬挂方式、均压环的形状及均压环的布置方式进行了耐雷电冲击特性试验,试验研究结果表明并联绝缘子串的雷击击穿电压较单串时低;开口状均压环的均压效果和引弧效果均优于闭口状均压环;均压环的开口方向与导线垂直时,可保护绝缘子和导线。