浅谈小浪底水力发电厂励磁系统改造

小浪底水力发电厂根据励磁系统的实际运行情况,对发电机励磁装置进行了必要的改造.本文介绍了小浪底电厂励磁现状及改造方案、改造后的unitrol5000系列励磁系统的特点,并针对机组励磁系统改造后的运行要求,对监控系统程序优化进行了分析.为同类水电站的励磁系统选型和改造提供了一定的借鉴作用.     

一种无刷励磁同步电机高速旋转整流器装置

旋转整流器是增安型无刷励磁同步电动机的重要组成部分，也是无刷励磁同步电机系统的核心。旋转整流器装置能在高速旋转的情况下将交流励磁机产生的交流电通过整流模块整流后变为直流电源输出。本文介绍一种能在高速旋转无刷直流电机中可靠工作的整流器装置。     

一起6kv无刷励磁同步电动机故障跳闸分析

针对6kv无刷励磁同步电动机试车过程中出现的故障跳闸现象,通过检查高压柜和励磁柜的二次回路以及高压柜综保的故障告警信息,分析高压电动机跳闸原因,找出症结所在,并提出了解决方案.     

发电机励磁方式的选择

随着发电机容量的不断增大,发电机电流也随之增大,对励磁系统的技术要求也更需要完善.本文对大型发电机励磁方式做了详细的介绍     

可控硅励磁系统起励故障原因排查分析

可控硅励磁屏在发电机励磁中电应用广泛,而可控硅的维护维修直接影响生产效益,正确、准确判断故障点是维护的关键,在更换元件时要确定元件极性后正确安装,如安装不正确将新增一个人为故障点,可能使故障点扩大。给维修带来一定的难度。     

电磁式无刷交流同步电机起动过程仿真研究

本文重点研究了电磁式无刷交流同步电机使用单相交流励磁起动方案的起动过程。作者在文中深入分析了起动过程中的相关问题。     

基于MATLAB的励磁系统仿真研究

励磁系统的基本功能是给同步发电机励磁绕组提供直流电流,励磁系统通过励磁电压控制转子磁势的大小,实现控制和保护功能。控制功能可以实现电压和无功潮流的控制并提高系统稳定性;保护功能可以保护同步电机、励磁系统和其他设备不超过容量极限。     

灯泡式贯流水轮发电机定子的选型与设计

贯流式水轮发电机组20世纪30年代问世以来,由于其优良的枝术经济特性而得到了广泛的应用,贯流技术也因此得到了迅速发展.我国是从20世纪60年代开始对灯泡式贯流机组进行研发的,本文重点介绍灯泡式贯流水轮发电机定子的选型与设计.     

走在时代前面的无锡电机厂

无锡电机厂成立于1958年,是国家二级企业,以生产各种船用电机为主。1980年和1985年先后从德国西门子公司引进1FC5,1FC6系列船用无刷三相同步发电机,至今已累计生产20000多台。1990年1FC5系列发电机获国家银质奖,国内制造的5000吨级以上各种船舶大部分选用该厂产品。该发电机还广泛用作石油开采、钻井平台、客车、核电站设备、邮电通讯及宾馆     

基于Simulink的电力系统稳定器（PSS）应用仿真

本文通过建立同步发电机的励磁系统模型,介绍了Matlab/Simulink仿真工具在电力系统仿真中的应用方法。针对不同故障类型,对发电机暂态参数在AVR控制和PSS控制下的暂态过程进行了仿真和比较。仿真结果证实,双输入PSS具有明显的抗故障干扰、抑制低频振荡能力,有助于提高电力系统的稳定性。     

Trade Reform and Poverty: The Case of Mexico

We use a two‐step computationally simple procedure to analyse the effects of Mexico's's potential unilateral tariff liberalisation on real incomes. First, we use the CGE model provided by the Global Trade Analysis Project (GTAP) as the new price generator. Second, we apply the price changes to Mexican household data in order to assess the effects of the policy simulation on poverty and income distribution. Although Mexico widely liberalised most of its imports by the mid 90s, one salient feature is its membership in the North American Free Trade Agreement (NAFTA) with Canada and United States. By choosing GTAP as the price generator, we are able to model the differential tariff structure. Even starting with a low level of tariff protection, simulation results show that the impact of tariff reform on welfare will be positive in general for all expenditure deciles. We find that, when we assume non‐homothetic individual preferences, trade liberalisation benefits people in the poorer deciles more than those in the richer ones.     

BDI指数与国内相关上市公司股价的灰色关联分析

BDI(波罗的海干散货运价指数)是由波罗的海航交所发布的代表国际航运市场,特别是干散货运市场的重要运价指数。近年来国内航运、港口类企业在资本市场上的表现受到BDI指数影响。国内企业和科研院所对BDI指数的研究很多,但未见从数量关系的角度系统地分析BDI指数和国内航运上市公司表现联动性机理的研究。因此,采用灰色关联分析方法研究对航运和港口类上市公司的作用为港口航运类公司的经营提供规避价格风险的依据,为港口航运类股票投资者提供了操作指引。     

无刷直流电机调速系统的最优状态反馈控制研究

本文研究具有量测噪声和负载干扰的无刷直流电动机实时最优速度控制方法。首先建立系统的硬件结构，并推导出系统的数学模型；接着采用卡尔曼滤波器的状态估计；提出了一种基于动态规划的最优反馈控制策略；最后给出了补偿量测噪声和负载干扰的自适应算法。仿照结果表明，提出的方法，在广宽的调速范围内，系统具有较好的静动态性能。验证了提出方法的有效性与可行性。     

Self-employment and allostatic load

Self-employment can be stressful and its long-term effects on individual health could be significant; yet, the physiological outcomes of self-employment related stress remain under-explored. Drawing on allostatic load as a long-term biological consequence of physiological wear-and-tear and an indicator of stress response, we use three different studies to provide a more nuanced understanding of the relationship between self-employment and physiological outcomes. In Study 1, based on a sample of 194 self-employed and 1511 employed individuals, we find that self-employment is marginally related to allostatic load and allostatic load marginally mediates the relationship between self-employment and physical, but not mental, health. Study 2, based on a sample of 776 self-employed and 8003 employed individuals, extends these findings, and provides evidence that those who are self-employed for longer periods have a higher allostatic load. Finally, in Study 3 we draw on a sample of 174 twins and, consistent with Study 2, show that those reporting self-employment in two waves (about eight years apart) had a higher allostatic load, however, when leveraging problem-focused coping such individuals experienced lower allostatic load. Taken together, these three studies extend our understanding of the relationship between self-employment and wellbeing.     

变结构／变初值准混沌滚动密钥产生器

本文首先指出传统的滚动密钥产生器，在滚动密钥生成的过程中，状态转移函数和输出函数的结构初值及其状态初值都是固定的不变的，因此，利用在道中截取足够长的数据，原则上，总是可以破译的。鉴于此，我们在数字或准混沌意义上，采用综合算法提出了变结构／变初值准混沌滚动密钥产生器，使之在滚动密钥的生成过程中，状态转移函数和输出函数每一个字节都更新一次结构初值和状态初值，且永不重复、不可预测。在未建立综合数字之前，     

花青素的提取、分离与纯化方法的研究进展

花青素因在天然植物中广泛存在及优异的抗氧化性能而受到研究者的普遍关注,加之近年来人们对从植物中提取分离花青素及纯化技术的研究深入,它在医药保健、化妆品、食品添加剂等领域的应用日益广泛。综述了国内外近几年提取分离花青素的技术及纯化方法,对各种方法的优缺点进行了分析,对花青素的研究现状做出总结并展望,旨在为花青素资源的开发利用和工业化生产提供依据。     

2009 China Market Suppliers List

Company Name： Fuzhou Changhua Power machinery Co.Ltd.
Company Profile： We are professional electric machinery manufacturer in china, which specializes in producing diesel and gasoline engine, diesel and gasoline generator, as well as diesel and gasoline water pump. Our company has obtained ISO9001 certification and Chinese national CCC certification, most of our products now have passed CE certification. Our products have been exported to more than 30 countries and regions, mainly in Europe, Southeast of Asia,     

无刷直流电动机离散变结构控制器设计与仿真

介绍了无刷直流电动机（BLDCM）位置伺服系统离散时间变结构控制器的设计方法。数字仿真结果表明：变结构控制器具有健全的控制性能，对控制对象的参数变化及外部扰动并不敏感，系统状态将按预定的路径变化，因而伺服系统具有高稳定性、高精度、鲁棒性和快速响应等优点。     

Teaching Media and Methods in Marketing: European and North American Universities

This article aims to examine the most widely used teaching media and methods in university education. To achieve this objective, international research has been carried out among 135 marketing teachers from North American and European universities. The study shows that North American teachers use more traditional media and participatory methods than European teachers.