Stator winding single-phase grounding faults protective scheme based on discriminant analysis for Powerformers with selectivity

In order to improve the stator winding single-phase grounding faults protective scheme for Powerformers, a protective scheme based on Mahal distance discriminant theory is proposed in this paper. By the proposed scheme, the different kinds of fault signals can be integrated. Also, a discriminant analysis model for stator winding single-phase grounding faults is established. In the proposed discriminant analysis model, four parameters including the magnitude of leakage current, the direction of leakage current, the magnitude of zero-sequence current in Powerformer terminal, and the direction of zero-sequence current in Powerformer terminal are selected as the discrimination factor. The method of back substitution estimation is introduced to verify the stability of the distance discriminant analysis model. Twenty-five groups of detected samples were analyzed based on the proposed model. The results are consistent with the measured data and show that the distance discriminant analysis model is with higher accuracy and lower mistake-discrimination ratio.     

A review and comparison of fault detection and diagnosis methods for squirrel-cage induction motors: State of the art

Preventing induction motors (IMs) from failure and shutdown is important to maintain functionality of many critical loads in industry and commerce. This paper provides a comprehensive review of fault detection and diagnosis (FDD) methods targeting all the four major types of faults in IMs. Popular FDD methods published up to 2010 are briefly introduced, while the focus of the review is laid on the state-of-the-art FDD techniques after 2010, i.e. in 2011–2015 and some in 2016. Different FDD methods are introduced and classified into four categories depending on their application domains, instead of on fault types like in many other reviews, to better reveal hidden connections and similarities of different FDD methods. Detailed comparisons of the reviewed papers after 2010 are given in tables for fast referring. Finally, a dedicated discussion session is provided, which presents recent developments, trends and remaining difficulties regarding to FDD of IMs, to inspire novel research ideas and new research possibilities.     

定子齿开槽对六相电机齿槽转矩的影响

针对六相永磁电机齿槽转矩过高引起振动和噪声问题,以一台12槽10极表贴式永磁电机为例,提出一种在定子齿开辅助槽的方法降低齿槽转矩。分析永磁电机齿槽转矩的工作原理,推导出齿槽转矩与开槽结构的解析关系;对定子齿开槽方法进行设计,进一步对辅助槽位置、数量和尺寸进行分析和优化;对开槽前后电机进行有限元仿真分析,并与初始电机进行性能对比。结果表明：定子齿开辅助槽对于抑制齿槽转矩有着显著作用,最大可减小约91.8%。结果验证了该方法的可行性和有效性。     

基于DSP的大中型异步电动机在线监测故障诊断系统设计

随着现代电子技术，计算机技术，信号处理技术和半导体制造技术的快速发展，近年来，数字信号处理器(Digital Signal Processor)作为一种专用的数字信号处理器件，以其对数字信号灵活的处理方法，强大快速的处理能力，在加上重复性好，稳定性高，性价比高等种种优点，正应用在越来越多的生产和生活领域，     

双作用叶片油泵定子曲线的改进设计

提出一种对双作用叶片油泵定子曲线改进设计的思路,改进定子的特点是增大吸油腔过渡曲线所占的角度范围,同时减小压油腔过渡曲线所占角度范围,使前者大于后者,这样可以使叶片在吸油腔的外伸速度和加速度减小,或者使定子曲线的升程增大,可增大油泵排量,改善油泵起动性能和吸油条件.     

G4051单螺杆计量泵故障诊断与处理

聚乙烯装置流化床反应器浆液催化剂加料泵是一种结构特殊的单螺杆泵。泵的螺杆总长 1 .2米 ,与氟橡胶内衬相配合。由于其精度高 ,因此 ,能起到精确计量的作用。这种类型的螺杆泵在国内使用较少 ,维修经验也很少。本文通过对G4 0 5 1螺杆泵故障原因的诊断分析 ,提出了有效的解决方案 ,节省了设备购置费 ,取得了较好的经济效益     

大中型立式电机机座的焊接工艺

对大中型立式电机钢板机座的焊接、热处理工艺进行研究,确定合理的焊接顺序及热处理工艺参数,测试残余应力变化,选取合理的热处理工艺及焊接工艺参数,获取整机焊后变形量数据,修正生产工艺,提高大型焊接结构件的尺寸稳定性。     

基于模糊输出BP神经网络的电机主绝缘老化状态评估方法

评估大电机主绝缘的老化状态是电气工程领域中的重要课题，其目标是根据非破坏性参量评估绝缘的老化状态，然而传统的评估方法一直没有得到准确可靠的评估结果。为了克服传统的绝缘状态阈值评估方法的缺点，提出应用神经网络和模糊数学结合评估绝缘状态的新方法。由于绝缘的老化状态是一种模糊现象，所以建立了具有模糊输出的3层BP神经网络对绝缘状态进行评估，并确定了绝缘状态论域上的四个模糊子集及其隶属函数，同时规定了网络的输入和输出参量。选择Levenberg-Marquardt快速学习算法对该文建立的模糊输出神经网络进行了训练，并使用另外10组多因子加速老化数据和5组真机线棒数据对网络的评估能力进行了检验，检验结果表明该方法可以准确有效地评估定子绝缘的老化状态。     

台达数控和伺服在定子绕线机控制系统中的应用

利用中达CNC数控系统精密的轴定位控制功能和台达伺服系统快速精确的动态响应特性，使绕线机的性能和工作效率得到了很大的提高。本文主要介绍了数控定子绕线机的功能需求、系统操作界面和I／0的规划。     

基于自适应PI在线补偿感应电机定子电阻

感应电机定子电阻变化是影响直接转矩控制低速性能的主要原因之一。该文分析了定子电阻变化对直接转矩控制性能的影响，并指出可能出现系统不稳定的现象。根据实际定子电流和给定定子电流的差值，提出了基于自适应PI的在线定子电阻补偿方法，解决了定予电阻对系统性能影响的问题。仿真结果表明，该文提出的方案能实现对实际定子电阻的辨识并对控制系统所采用定子电阻在线补偿，从而改善了直接转矩控制系统的低速性能。