一起发电机定子接地故障的分析与处理

文章介绍了海外某大型火力发电厂发生的一起发电机定子接地故障的分析和处理过程,对发电厂类似故障的处理和海外发电厂的运行和维护提供了参考。     

Experimental investigation of unconfined spherical and cylindrical flame propagation in hydrogen-air mixtures

This paper presents results of experimental investigations on spherical and cylindrical flame propagation in pre-mixed H₂/air-mixtures in unconfined and semi-confined geometries. The experiments were performed in a facility consisting of two transparent solid walls with 1 m² area and four weak side walls made from thin plastic film. The gap size between the solid walls was varied stepwise from thin layer geometry (6 mm) to cube geometry (1 m). A wide range of H₂/air-mixtures with volumetric hydrogen concentrations from 10% to 45% H₂ was ignited between the transparent solid walls. The propagating flame front and its structure was observed with a large scale high speed shadow system. Results of spherical and cylindrical flame propagation up to a radius of 0.5 m were analyzed. The presented spherical burning velocity model is used to discuss the self-acceleration phenomena in unconfined and unobstructed pre-mixed H₂/air flames.     

Effect of grinding-induced cyclic heating on the hardened layer generation in the plunge grinding of a cylindrical component

This paper discusses the effects of the grinding-induced cyclic heating on the properties of the hardened layer in a plunge cylindrical grinding process on the high strength steel EN26. It was found that a multi-pass grinding brings about a uniform and continuous hardened layer along the circumference of the cylindrical workpiece. An increase of the number of grinding passes, leads to a thicker layer of hardening, a larger compressive residual stress and a deeper plastic deformation zone. Within the plastic deformation zone, the martensitic grains are refined by the thermo-mechanical loading, giving rise to a hardness of 12.5% higher than that from a conventional martensitic transformation. The coupled effects of heat accumulation and wheel wear in the multi-pass grinding are the main causes for the thickening of the hardened layer. A too small infeed per workpiece revolution would result in insufficient grinding heat, and in turn, bring about an undesirable tempered hardened layer and a reduction of its hardness.     

压电超声微电机混合结构定子的固有频率特性分析

压电超声微电机是依靠定子振动变换能的功率器件，定子性能将直接关系到微电机能否实现，本文采用Ｒａｙｌｅｉｇｈ－Ｒｉｔｚ方法来分析机械中经常采用的多层膜结构（混合结构）定子的固有振动特性，推导中考虑了平面应力和弯曲应力对固有频率的影响，模拟计算和实验结果符合得较好，此外还讨论了定子有关参数对固有频率的影响。     

国产550MW水轮发电机用新材料和新工艺

介绍了二滩水电站 5 5 0MW机组发电机定转子绕组方面所采取的新结构、新工艺和新材料     

介质加载圆柱腔的场分析

本文应用严格场匹配法解决了介质加载圆柱腔的本征问题，计算了圆柱腔在纵向部分填充介质后ＴＥ０１ｎ模和ＴＭ０１ｎ模的本征频率和本征场型的变化。特别分析了本征模式在空气段为截止模的情况。本文的分析方法亦可应用到纵向部分填充介质的传输线和其它形状的谐振腔。     

水轮发电机定子浮动式双鸽尾筋调整工艺浅析

水轮发电机定子采用浮动式双鸽尾筋是当今设计上较为先进的结构,是防止定子铁心变形的重要措施之一,制造厂一般会提供安装调整的工艺措施,但此工艺措施更多的是检查的标准,对如何具体操作不够详细,安装调整完全依靠施工人员的经验进行。如何有针对性的分析调整工艺中的难点和易忽略点,提出更具指导性的调整工艺,成为了一个需研究的课题。     

三峡发电机定子线棒铜空心导体的腐蚀研究

根据三峡水力发电厂水轮发电机定子纯水冷却系统的组成情况,建立模拟试验装置。研究了定子线棒空心铜导线试片在微碱性条件下(pH为8.0~8.5)的腐蚀特性。采用树脂洗脱法测定腐蚀速率,采用扫描电镜分析法观察试片的表面形貌。试验结果表明铜导线腐蚀速率为26.5 g/(m2.a)。     

不甩线圈的多星形移相变极

对于某些槽数和极数比的多星形移相变极电机,提出与前人不同的是在两种极数下均不甩去线圈的绕组方案,使绕组利用率高,且线圈及其联接都较简单.这种绕组方案在一种极数下并联支路略有不平衡,其所引起的电机定子铜耗的增加是极其有限的,不致影响电机的正常运行.