变频电机匝间绝缘损坏的探讨

针对交流变频电机早期匝间绝缘损坏的特性,探寻变频电机匝间绝缘损坏机理,提出提高匝间绝缘强度的控制措施。     

变频调速异步电机的设计重点

本文比这从系统的角度对变频电机在电磁设计、耐电晕绝缘系统、轴承绝缘拽术、结构设计方面及一些个人经验,以此阐述了交流调速系统的特点及逆变器运行时对变频电机工作的影响.     

进口变频电机大修国产化技术

以275kW日立产变频电机为例，阐述了在现有工装设备和工艺条件下的电机大修施工方案、国产绝缘材料和绝缘结构的替代方案以及部分工艺难点的解决办法。     

变频调速电动机的应用分析

分析了变频调速异步电动机的转矩转速特性，指出变频电压调速对电机效率、电机工作温度、电动机绝缘结构承受冲击电压的能力、谐波电磁噪声与震动、电动机对频繁起制动的适应能力、低速时的冷却等影响较大，提出应减小定子电阻、提高转子电阻、合理设计漏电感应主磁路以改善电动机对非正弦电源波形的适应能力；改善电动机结构以减小非正弦波对电动机的绝缘结构、震动、噪音、冷却方式的影响。     

抗电晕漆包线的研制及机理探讨

近年来国外交流电机变频调速技术正在迅速发展,在冶金、矿山、机电、石化、铁路、电梯、水泵、家电等诸多领域都需应用。因此交流高频电机绝缘结构和新型绝缘材料的研制成为各国的前沿研究课题。抗电晕漆包线可使交流高频电机的寿命提高数十倍以上,适用于交流高频电机使用的抗电晕漆包线将是很有发展前途的漆包线新品种。介绍了抗电晕线的研制,主要包括涂料、母材、涂覆工艺的研制,同时探讨了耐电晕机理。     

PWM变频器用于异步电机应注意的设计施工问题

1引言PWM变频调速已成为异步电机最主要的调速方法。由于PWM变频器的输出电压为非正弦波包含有大量的谐波。变频调速将引起谐波干扰及发热问题,变频器与电机的选择等问题。在设计施工中应特别注意这些问题,并采取相应措施减少谐波的危害。2设计选型措施2.1防电机过热措施每种电动机都有最高的升温限制。电机绕组所允许的最高温度与使用的绝缘材有关。在设计电机时,是针对正弦波及电机运行在基速情况下考虑发热问题的。使用PWM变频器将会使用电机发热增加。其主要原因如下:PWM变频器输出波形存在着谐波成分,这会使电机产生谐波铜损和铁…     

变频电机有关问题的探讨

从电机理论和电路分析理论出发，对交流变频传动系统中的交流电机的运行情况作了较为深入的分析；从系统的观点讨论控制系统与电机的相互影响及相互制约的关系，由此基础上给出了变频电机的概念及内涵，对各类变频传动系统中变频电机的设计、制造、选型、应用试验提出了系统的要求和原则性结论，在变频传动理论和工程应用方面有一定的指导意义。     

国产变频异步电动机在高线粗、中、预精轧机中的应用

新疆钢铁公司高速线材厂设计年产量为４０万ｔ ,主要产品规格为Φ５ ０～２０ｍｍ圆钢和Φ８～１６ｍｍ螺纹钢 ,最大轧制速度１１０ｍ／ｓ。１８架粗、中、预精轧机均由摩根设计国内制造 ,配备了上海电机厂生产的ＹＢＦＪ５００ ４交流变频异步电动机 ,主传动变频装置采用意大利ＡＮＳＡＬ ＤＯ公司ＳＶＴＬ变频器。电机配置４００ｋＷ７５０／１５００ｒ／ｍｉｎ ,６００ｋＷ、７００ｋＷ９００/１８００ｒ／ｍｉｎ。１交流变频异步电动机变频器因采用各种类型的ＰＷＭ调制技术 ,其输出所含的高次谐波电压、电流将严重影响电机的绝缘强度并…     

宝钢轧机主传动电机的特点

宝钢轧机主传动电机全为西门子、BBC、日立等公司的产品,它们虽仍以直流电机为主,但已开始采用西门子公司提供的交交变频供电、矢量控制的交流传动,代表了当前轧钢电机的发展方向。所用直流电机全为可控硅供电,F级、甚至H级绝缘,尽量系列化和通用化以提高互换性。由于这些公司的精心设计,取用了许多新结构、新材料,使电机具有较高的经济技术指标,代表了70年代未、80年代初的世界先进水平,为提高我国电机制造水平、发展轧钢生产提供了榜样。     

长导线对变频器控制电机的影响及解决办法

变频器及变频电机已普遍应用于工厂的各个领域，变频电机的损坏也日益突出。本文分析了长导线对变频器控制电机的影响，以杭钢线材轧机的变频电机损坏为例，进行机理分析，并给出解决办法，以防止电机的进一步损坏，确保生产的正常进行。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

Quality of life of relatives of mental patients

Usage of quality of life of psychiatric patients' relatives as the parameter of estimation of the quality of psychiatric care is considered. By means of standard questionnaire elaborated by the authors as well as by means of both individual and group conversations the quality of life was analyzed in 40 relatives which lived together with psychiatric patients. Different spheres of their life and difficulties (financial, social-psychologic, production) were examined in families with such patients. The defects of psychiatric care that had direct influence on the quality of life of the psychiatric patients' relatives are outlined.     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.