轴电流产生及轴电流保护装置应用分析

主要对轴电流的产生原因，BZL-10C型发电机轴电流保护装置的工作原理、现场安装及故障分析处理。     

水电厂发电机组轴电流相关问题探讨

确保水电站稳定、灵活、可靠和经济地生产电能，对加速我国水电事业的发展具有重大的意义。科学技术的进步，促进了水轮发电机组朝大型化方向发展的速度，使它在电网中发挥着举足轻重的作用。     

变频电机轴电流分析及对策

轴电流的存在对电动机轴承的使用寿命具有极大的破坏性，根据现场实际运行情况，分析其产生的原因，采取有效措施，从根本上解决轴电流危害的问题．     

引风机电动机轴承故障诊断分析

由于设计、安装、运行等原因,电动机轴电压一般无法避免,为避免轴电流的产生,通常情况下变频电动机需要安装绝缘轴承,但是绝缘轴承的成本太高,普遍应用性爱到很大制约。本文介绍了变频电动机轴电流的产生及对轴承的影响,利用振动检测技术检测变频电机轴承故障。     

低压大功率变频电机轴电流的分析与处理

对低压大功率调频电机的轴承频繁损坏的原因进行分析及说明处理方法,指出轴电流产生的基本原因,以及如何消除轴电流的处理方法。     

电机轴电流的危害及防止措施

在电动机运行过程中,如果在两轴承端,电机轴与轴承间有轴电流的存在,对电机轴承造成烧损。那么电机轴承的使用寿命将会大大缩短。轻微的可运行上千小时,严重的甚至只能运行几小时,给现场安全生产带来极大的影响。同时由于轴承的损坏及更换带来的直接和间接经济损失也不可小计。     

轴电流损伤球轴承的载荷分布和刚度变化分析EI北大核心CSCD

基于轴电流损伤凹坑的表面形貌,提出故障表征模型,对损伤后角接触球轴承的载荷分布和刚度变化进行研究。首先,建立了考虑弹性接触和滚动体与滚道间相互作用力的角接触球轴承分析模型,并验证模型的准确性;其次,提出了具有不同长度、宽度、深度的轴电流外滚道损伤凹坑的故障模型及分段函数表达式;最后,利用该故障模型研究了具有不同大小和形状的轴电流损伤凹坑对轴承载荷分布和刚度变化的影响。结果表明:滚动体从滚入到滚出轴电流损伤凹坑过程中,将释放一定量变形,导致损伤区域轴承承载力部分或全部丧失;随着轴电流损伤凹坑变大,轴承刚度变化更大、更迅速。     

浅谈双馈风电机组发电机轴承维护

目前,随着变频技术的逐步发展,双馈风力发电机组在国内使用的最为广泛,而其发电机轴承故障在机组大部件故障中占有很大的比例,给设备的安全稳定运行带来极大的安全隐患。本文从双馈发电机工作的原理、发电机轴承运行的工况等方面分析轴承故障的原因,进而提出发电机轴承维护的有效措施。     

纯电动公交车用永磁无刷直驱电机可靠性研究

针对纯电动公交车运行工况，设计了具有功率体积比高、输出转矩大、特别在启动提速阶段要提供强大驱动力的双速永磁无厣J电动机，提出了增强纯电动公交车用永磁无刷直驱电机可靠性的措施，通过对电机系统可靠性研究与实践，将推进纯电动公交车产业化发展。     

轴电流保护动作的原因查找和防范措施

介绍飞来峡水电厂水轮发电机轴电流的产生原因,结合机组投运以来不同故障类型的发电机轴电流保护动作的查找和处理,并提出防范措施。     

脉冲电流烧结机理的研究进展

脉冲电流烧结（Ｐｕｌｓｅ ｅｌｅｃｔｒｉｃ ｃｕｒｒｅｎｔ ｓｉｎｔｅｒｉｎｇ,ＰＥＣＳ）是材料科学领域开发出的一种新型快速烧结技术,已广泛应用于金属与合金、结构陶瓷、氧化物超导体、复合材料、热电材料、高分子材料以及功能梯度材料的制备．本文简介脉冲电流烧结特征,结合ＰＥＣＳ烧结条件对铜粉末和氧化铝粉体致密化及显微结构影响的实验证据,就脉冲电流烧结过程和机理进行探讨．     

丝带型电流引线热损耗实验

搭建了电流引线热损耗实验装置,设计了丝带型电流引线结构,测量了其在负载0—500 A电流时温度分布,并估算了其在相应电流负荷下热损耗。实验表明:电流引线的温度随负载电流的增加而升高,电流引线热损耗随负载电流的增加先略有降低后升高。     

Electromagnetic behavior of lap-joints for fusion magnet system

The joint between superconducting Cable-In-Conduit-Conductors (CICC) is a key technology in a magnetic confinement fusion apparatus. Several hundreds of joints are involved in one apparatus generally. DC resistance of the lap-joint is typically designed less than several n-ohms and the allowable joule loss is several watts. AC loss due to external magnetic field is also limited to less than several watts. Reduction of the AC loss and low joint resistance are required simultaneously and those are conflicting trade-off.The lap-joint had been examined under both self-field and external-transverse-field experimentally. In this study, we established a numerical model for the joint and analyzed for electromagnetic behavior of it numerically. In the simulation, modeling of contact resistances between twisted strands is important. Circuit constants, e.g., conductance between strands, were determined to reproduce the experimental results; those are the circuit constants and the DC joint resistance. The relation between the joint resistance and the AC loss was discussed. Constitution of the joint does not only influence on the joint resistance and the AC loss but also current distribution in the cable. Non-uniform current distribution among the strands is reported to result in the degradation of the stability. We successfully simulated mentioned phenomena and found our numerical model was useful in joint design to find a good compromise.     

Theoretical Analysis and Numerical Simulation of the Feasibility of Inspecting Nonferromagnetic Conductors by an MFL Testing Apparatus

ABSTRACT

It has been widely accepted that the magnetic flux leakage (MFL) testing system can be applied only to the inspection of ferromagnetic materials. The possibility of using the MFL testing apparatus to inspect nonferromagnetic metals is discussed in this article. According to Faraday’s law of induction, eddy current rises in the conductor passing through the MFL magnetizer. The perturbation of eddy current and its corresponding magnetic field caused by defects are theoretically analyzed. Then, the finite element method is carried out to verify the theoretical analyses and extract the perturbed magnetic field signals. Furthermore, the influences of specimen conductivity and moving velocity on the detection signal amplitude are also simulated. The results show that the nonferromagnetic conductors are possible to be inspected by the MFL apparatus, and higher conductivity or inspection speed will facilitate the inspection.     

高速往复运动机构重复定位精度测量技术研究

本文提出了一种高速往复运动机构重复定位精度测量技术，利用该项技术可以方便地测量出亚微米级的机构高速运动重复定位精度。本文论述了采用电涡流法测量的基本原理，解决了传感器设计与制造、测量电路设计和实验等一系列技术问题。本文为机械加工设备及各种动力机械的研究和生产提供了一种新的测试手段．     

交流杂散电流作用下碳钢在土壤模拟溶液中的腐蚀

深入研究碳钢在交流作用下的腐蚀状况具有十分重要的意义。采用自行设计搭建的交流电流腐蚀试验装置,通过测试碳钢接地材料在土壤模拟溶液中的腐蚀电位、电化学曲线及腐蚀失重数据,对其在交流电杂散电流作用下的腐蚀状况进行研究,以期掌握在交流杂散电流作用下土壤中碳钢的腐蚀倾向和速率。结果表明:在杂散电流作用下,碳钢在土壤模拟溶液中的腐蚀倾向增大,且碳钢的腐蚀速率随着电流密度的增大而加快。     

调速型鼠笼式异步磁力联轴器的轴向力研究

调速型鼠笼式异步磁力联轴器即永磁调速器,它的力学参数、磁场分布对其传递能力及整个系统的稳定性与可靠性具有很大的影响,因此有必要对其工作时的轴向力进行深入研究.基于等效面电流法,推导出联轴器在低转差率下的螺旋进给/退出轴向力计算表达式;同时采用电磁场分析软件Magnet对其进行模拟分析,得到了不同啮合长度、不同转差率下的螺旋进给/退出轴向力值,并进行了对比分析.调速型鼠笼式异步磁力联轴器轴向力由完全啮合状态至脱离状态呈现先增大后减小的趋势;在相同输入转速情况下,转差率越大,轴向力越小,在脱离状态时趋于稳定值.这对于调速型鼠笼式异步磁力联轴器以及其它类型磁力联轴器的理论研究、参数设计与优化及其应用都有着一定的理论意义及实际应用价值.     

电流脉冲加热瞬态热物性测量技术

对国内外电流脉冲加热技术的发展状况进行了综述评价.针对获取温度方法不同,主要介绍了黑体法、积分球法和激光偏振法三种基本形式的测量系统,进而介绍了扩展参数测量装置.又较为详细地介绍了作者自己研制的测量装置和特点.最后作者展望了电流脉冲加热技术的最新研究动态和发展方向.     

碳纤维增强复合材料雷击损伤实验及电-热耦合仿真

为了研究碳纤维增强复合材料(CFRP)在雷电流作用下的损伤规律,对CFRP进行了雷电流直接效应实验和电-热耦合效应仿真。首先,利用冲击电流发生装置进行了雷电流的直接效应实验,对比了不同电流峰值情况下CFRP的表面损伤情况,并通过C扫描观察了内部损伤。实验结果表明:CFRP的损伤范围随电流峰值增大而显著增大,且内部损伤的范围远大于表面损伤的范围。之后,对试件进行了电-热耦合有限元分析,并利用叠加的温度场范围近似表示内部损伤的范围,与实验结果的对比说明了此方法的有效性。不同类型及不同作用积分的冲击电流作用下的电-热耦合分析结果表明,作用积分是影响损伤范围的重要因素。     

Probing Access Resistance of Solid-state Nanopores with a Scanning Probe Microscope Tip

An apparatus that integrates solid-state nanopore ionic current measurement with a scanning-probe microscope is developed. When a micrometer-scale scanning-probe tip is near a voltage-biased nanometer-scale pore (10–100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, the relative pore resistance increases due to the tip and ΔR/R0 is estimated as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ΔR/R0 also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, ≈10 nm, experiments show that ΔR/R0 depends on salt concentration as predicted by the Poisson and Nernst–Planck equations. Furthermore, the measurements show that ΔR/R0 goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally; they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip.