基于显微组织的MOV在不同冲击条件下的破坏机理研究

发布时间：2018-03-25 02:16

  本文选题：MOV　切入点：结晶度　出处：《南京信息工程大学》2016年硕士论文

【摘要】：针对MOV在10/350 ps波形和8/20 μ s波形冲击下的破坏的问题,本文使用扫描电镜(SEM)结合材料成分分析X射线衍射仪(XRD)研究了氧化锌压敏电阻(MOV)在高电压冲击过程中伴随的物质变化,从微观结构及组分角度分析MOV在电涌冲击下的破坏机理。研究表明：在8/20μ s波形冲击破坏后期,MOV中的Sb203对整体致密性的控制能力明显下降,内部晶粒尺寸有所增加,晶界面之间有挤压破坏的特征；在10/350μ s波形冲击破坏过程中,大量的热量会造成MOV中Bi2O3的逐渐挥发,从而导致MOV内部离子迁移不均匀；8/20 μ s波形冲击下破裂损坏的MOV内部微观结构并不一定发生很大的变化,受破坏程度与冲击次数有关；但无论遭受哪种类型的冲击破坏,MOV的破坏实质是内部的微观物质由晶态逐渐转变成半晶态过程。针对MOV在单次8/20μ s波形和同时序多次脉冲冲击下的破坏问题,本文基于黑龙江省防雷中心的多脉冲冲击平台,采用XRD-Rietveld全谱拟合法和SEM-EDS分析研究了氧化锌压敏电阻(MOV)在单脉冲与多脉冲冲击条件下的破坏机理,以压敏电压(U1mA)和漏电流(Iie)为自变量建立了对MOV结晶度的预测模型。研究表明：脉冲之间的时间间隔对MOV的寿命长短有很大的影响；在单脉冲的冲击破坏实验中Bi203与尖晶石中Bi12ZnO20之间会相互转化,而在多脉冲的冲击下各MOV的受损存在差异,有的与单脉冲的破坏类似,有的MOV在大电流冲击下温度升高会引起Bi203的挥发,造成MOV穿孔破坏；但在任何冲击条件下,MOV的破坏实质都是内部的各微观成分由晶态逐渐变为半晶态过程。针对MOV多片并联在冲击老化过程中各阀片的配合问题,本文通过冲击实验,红外温枪测温,SEM扫描电镜分析表征等实验手段研究了MOV多片并联在冲击老化过程中温度差的变化。研究表明：在长期电涌冲击下,并联体中各MOV受损情况不尽相同,受损较严重的MOV甚至会出现穿晶破坏现象,将导致其阻性与其他MOV的阻性产生很大差异,当再次经受电涌冲击时其将会吸收更多的冲击电流,这样就会造成各MOV的通流量不同,从而产生温度差。根据此现象,设计了一种嵌入式多点温度无线监控系统,该系统能判断电涌保护器中各MOV的配合情况以及整体的老化程度,具有针对性强,实时高效的特点。
[Abstract]:In order to solve the damage problem of MOV under the shock of 10 / 350 PS and 8 / 20 渭 s waveforms, the material changes of ZnO varistors during high voltage shock were studied by means of scanning electron microscopy (SEM) and material composition analysis (XRD). The failure mechanism of MOV under surge impact is analyzed from the point of view of microstructure and composition. The results show that the control ability of Sb203 in 8 / 20 渭 s wave shock damage is obviously decreased, and the internal grain size is increased. During the impact failure process of 10 / 350 渭 s wave, a large amount of heat will cause the gradual volatilization of Bi2O3 in MOV. As a result, the internal microstructure of MOV which is damaged by 8 / 20 渭 s waveforms of non-uniform ion migration is not necessarily changed greatly, and the degree of damage is related to the number of shocks. However, no matter what type of shock damage the MOV is subjected to, the essence of the damage is the gradual transformation of the internal microscopic matter from crystalline to semi-crystalline state. In view of the failure problem of MOV under a single 8 / 20 渭 s waveform and simultaneous sequential multiple pulses, Based on the multi-pulse impact platform in the lightning protection center of Heilongjiang Province, the failure mechanism of ZnO varistor under single pulse and multi-pulse impact is studied by XRD-Rietveld full-spectrum fitting and SEM-EDS analysis. The prediction model of MOV crystallinity was established using varistor voltage U1mAand leakage current as independent variables. The results show that the time interval between pulses has a great influence on the lifetime of MOV. In the single pulse impact failure experiment, the Bi203 and Bi12ZnO20 in spinel transform each other, but the damage of each MOV is different under the impact of multiple pulses, some of them are similar to the damage of single pulse. Some MOV under the impact of high current temperature will cause Bi203 volatilization, resulting in MOV perforation damage; However, under any impact conditions, the essence of the failure of MOV is the gradual transformation of the microcosmic components from crystalline to semi-crystalline. In view of the problem of the matching of various valves in parallel connection of MOV during impact aging, the impact experiments are carried out in this paper. The change of temperature difference during shock aging of MOV was studied by means of scanning electron microscope (SEM) analysis and characterization of infrared thermometer. The results showed that the damage of MOV in the parallel was different under long term surge shock. The more severely damaged MOV may even have transgranular breakage, which will lead to a great difference between its resistance and that of other MOV. When it is subjected to the surge shock again, it will absorb more shock current, which will result in different flux of each MOV. According to this phenomenon, an embedded multi-point temperature wireless monitoring system is designed. The system can judge the coordination of MOV in surge protector and the aging degree of the whole system. It has the characteristics of strong pertinence and high efficiency in real time.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM862;P427.3
，

本文编号：1661094