本文選題：氧化鋅壓敏電阻 + 老化劣化　； 參考：《南京信息工程大學(xué)》2015年碩士論文

【摘要】：低壓配電系統(tǒng)中電涌保護(hù)器(SPD)是現(xiàn)代防雷技術(shù)中重要環(huán)節(jié)之一。而SPD因各種因素造成的老化劣化會令其失效,無法保護(hù)后續(xù)電路系統(tǒng)安全,造成嚴(yán)重后果。目前的防雷技術(shù)無法精準(zhǔn)的動態(tài)判斷SPD瞬時老化劣化程度,也就無法根據(jù)保護(hù)等級需要及時更換SPD,產(chǎn)生極大隱患。針對交流環(huán)境中氧化鋅壓敏電阻芯片熱熔穿熱劣化過程中散熱能力的研究對試驗依賴性強(qiáng)的問題,在分析MOV芯片散熱能力基礎(chǔ)上,提出了利用瞬態(tài)熱阻抗參量表述其散熱特性,建立了適用于MOV芯片的瞬態(tài)熱阻抗模型,研究了片徑和熱熔穿電流對MOV芯片瞬時散熱能力的影響。實驗結(jié)果表明,熱熔穿過程中,MOV芯片散熱量除與片徑有關(guān)外,還與通過電流值有關(guān),是一隨時間和溫度變化的量,并且隨著通電時間延長其晶界勢壘高度降低同時散熱能力增強(qiáng)。實驗結(jié)果驗證了模型的正確性,說明了所建立的瞬態(tài)熱阻抗模型可定量反映MOV芯片散熱能力大小。針對氧化鋅壓敏電阻芯片在8/20ps電流沖擊初期,芯片壓敏電壓變化較小,老化程度無法通過靜態(tài)參數(shù)判別的問題,設(shè)計了沖擊老化試驗,研究了ZnO壓敏電阻芯片不同沖擊老化情況,耐受工頻恒定不同幅值過電壓過程和耐受階段流經(jīng)芯片內(nèi)部電流Iin隨時間的變化關(guān)系；結(jié)合雙肖特基勢壘理論和ZnO壓敏電阻芯片Voronoi網(wǎng)格微觀結(jié)構(gòu)模型,分析試驗結(jié)論。研究表明：耐受工頻恒定相同幅值過電壓,ZnO壓敏電阻芯片經(jīng)8/20μs電流沖擊后老化程度越深其流過芯片內(nèi)部電流Iin的初始值越大；且Iin值隨時問上升速率與初始沖擊老化程度呈正比；相同老化程度ZnO壓敏電阻芯片耐受過電壓幅值越大,耐受時間越短,Iin的初始值越大。針對氧化鋅壓敏電阻芯片在實際工作環(huán)境中會遭受過電壓作用問題,設(shè)計了暫態(tài)過電壓預(yù)處理后MOV耐受沖擊老化試驗,研究了不同幅值工頻交流暫態(tài)過電壓5s作用下MOV芯片耐沖擊老化性能變化。試驗結(jié)果表明：MOV芯片經(jīng)暫態(tài)過電壓預(yù)處理后壓敏電壓升高,耐8/20μs電流波沖擊次數(shù)增多；暫態(tài)過電壓預(yù)處理后芯片沖擊過程中壓敏電壓呈現(xiàn)下降一保持一下降過程,與未經(jīng)預(yù)處理芯片壓敏電壓變化過程有所不同。結(jié)合雙肖特基勢壘導(dǎo)電機(jī)理推論出工頻交流瞬時過電壓作用下,氧化鋅晶界兩側(cè)勢壘高度變化過程,并經(jīng)過試驗數(shù)據(jù)分析證明此推論的合理性。
[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.
【學(xué)位授予單位】：南京信息工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM862;TM54

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