基于多种老化模型的氧化锌压敏电阻损坏模式研究

发布时间：2018-04-10 13:51

本文选题：氧化锌压敏电阻 + 老化劣化　；参考：《南京信息工程大学》2015年硕士论文

【摘要】：低压配电系统中电涌保护器(SPD)是现代防雷技术中重要环节之一。而SPD因各种因素造成的老化劣化会令其失效,无法保护后续电路系统安全,造成严重后果。目前的防雷技术无法精准的动态判断SPD瞬时老化劣化程度,也就无法根据保护等级需要及时更换SPD,产生极大隐患。针对交流环境中氧化锌压敏电阻芯片热熔穿热劣化过程中散热能力的研究对试验依赖性强的问题,在分析MOV芯片散热能力基础上,提出了利用瞬态热阻抗参量表述其散热特性,建立了适用于MOV芯片的瞬态热阻抗模型,研究了片径和热熔穿电流对MOV芯片瞬时散热能力的影响。实验结果表明,热熔穿过程中,MOV芯片散热量除与片径有关外,还与通过电流值有关,是一随时间和温度变化的量,并且随着通电时间延长其晶界势垒高度降低同时散热能力增强。实验结果验证了模型的正确性,说明了所建立的瞬态热阻抗模型可定量反映MOV芯片散热能力大小。针对氧化锌压敏电阻芯片在8/20ps电流冲击初期,芯片压敏电压变化较小,老化程度无法通过静态参数判别的问题,设计了冲击老化试验,研究了ZnO压敏电阻芯片不同冲击老化情况,耐受工频恒定不同幅值过电压过程和耐受阶段流经芯片内部电流Iin随时间的变化关系；结合双肖特基势垒理论和ZnO压敏电阻芯片Voronoi网格微观结构模型,分析试验结论。研究表明：耐受工频恒定相同幅值过电压,ZnO压敏电阻芯片经8/20μs电流冲击后老化程度越深其流过芯片内部电流Iin的初始值越大；且Iin值随时问上升速率与初始冲击老化程度呈正比；相同老化程度ZnO压敏电阻芯片耐受过电压幅值越大,耐受时间越短,Iin的初始值越大。针对氧化锌压敏电阻芯片在实际工作环境中会遭受过电压作用问题,设计了暂态过电压预处理后MOV耐受冲击老化试验,研究了不同幅值工频交流暂态过电压5s作用下MOV芯片耐冲击老化性能变化。试验结果表明：MOV芯片经暂态过电压预处理后压敏电压升高,耐8/20μs电流波冲击次数增多；暂态过电压预处理后芯片冲击过程中压敏电压呈现下降一保持一下降过程,与未经预处理芯片压敏电压变化过程有所不同。结合双肖特基势垒导电机理推论出工频交流瞬时过电压作用下,氧化锌晶界两侧势垒高度变化过程,并经过试验数据分析证明此推论的合理性。
[Abstract]:Surge protector (SPD) in low voltage distribution system is one of the important links in modern lightning protection technology.However, the aging and deterioration of SPD due to various factors will invalidate it and can not protect the safety of subsequent circuit system, which will result in serious consequences.The current lightning protection technology can not accurately and dynamically judge the deterioration degree of transient aging of SPD, so it can not be changed in time according to the need of protection grade, which has great hidden trouble.In order to solve the problem that the research of heat dissipation ability of ZnO varistor chip in alternating current environment is dependent on the test, based on the analysis of the heat dissipation ability of MOV chip, the transient thermal impedance parameter is proposed to express its heat dissipation characteristics.A transient thermal impedance model suitable for MOV chip is established. The influence of chip diameter and hot melt current on the transient heat dissipation capacity of MOV chip is studied.The experimental results show that the heat dissipation of MOV chip is not only related to the diameter of the chip, but also to the current value, which is a quantity varying with time and temperature.The height of grain boundary barrier decreases and the heat dissipation capacity increases with the prolongation of the time of electrification.The experimental results verify the correctness of the model and show that the established transient thermal impedance model can quantitatively reflect the heat dissipation capacity of MOV chip.Aiming at the problem that the voltage of zinc oxide varistor chip changed little in the early stage of 8/20ps current shock, the aging degree of the chip could not be judged by static parameters, the impact aging test was designed.In this paper, the variation of Iin in the internal current of ZnO varistor chip with different impact aging conditions, the process of withstanding constant power frequency and different amplitudes of overvoltage, and the flow through the chip in tolerant stage with time are studied.Based on the double Schottky barrier theory and the Voronoi mesh microstructure model of ZnO varistor chip, the experimental results are analyzed.The results show that the deeper the aging degree of the varistor chip subjected to 8 / 20 渭 s current impact, the greater the initial value of the current Iin flowing through the chip.The rise rate of Iin is directly proportional to the initial impact aging degree, and the larger the overvoltage amplitude of ZnO varistor chip with the same aging degree, the larger the initial value of the short endurance time.In order to solve the problem that zinc oxide varistor chip will be subjected to overvoltage in actual working environment, the MOV shock aging resistance test after transient overvoltage pretreatment is designed.The impact aging resistance of MOV chip under the action of AC transient overvoltage of different amplitudes was studied.The experimental results show that the voltage-sensitive voltage increases after transient overvoltage pretreatment, and the impulse times of 8 / 20 渭 s current wave increase after transient overvoltage pretreatment, and the voltage-sensitive voltage decreases, maintains and decreases during the transient over-voltage pretreatment.The process of variable-voltage change is different from that of unpreprocessed chip.Based on the conduction mechanism of double Schottky barrier, the variation process of barrier height on both sides of zinc oxide grain boundary is deduced under the action of transient overvoltage of power frequency AC, and the rationality of the inference is proved by the analysis of experimental data.
【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】：2015
【分类号】：TM862;TM54

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