【作者】 张沛红；

【导师】 雷清泉；

【作者基本信息】 哈尔滨理工大学 ， 高电压与绝缘技术， 2006， 博士

【摘要】 纳米科学技术的发展为新材料的开发和对现有材料的改性提供了新的思路和途径,纳米介质的出现,开辟了电介质新的应用领域。与传统介质比较,纳米复合介质的电、热、机械性能有了很大的改善。随着电力电子技术及新型半导体器件的迅速发展,八十年代以后,越来越多的交流变频调速电动机得到了广泛应用。由于局部放电等原因,许多变频电机的寿命只有1-2年,甚至有些电机在试运行阶段就发生击穿破坏。美国Dupont公司与ABB、西门子公司合作,于1995年研制出耐电晕聚酰亚胺薄膜,其耐电晕时间在20kV/mm场强下可达105小时,接近云母纸水平,但是没有见到从电介质理论的角度对其耐电晕机理进行深入研究的报道。本文借助扫描电镜和原子力显微镜分析了Dupont耐电晕聚酰亚胺薄膜的结构,比较了电晕老化后原始和耐电晕聚酰亚胺薄膜的表面形貌,得出Dupont耐电晕聚酰亚胺薄膜是三层结构,上下两个表层中含有较多的Al-无机化合物,是无机-有机复合结构。耐电晕聚酰亚胺薄膜之所以耐电晕,可能是因为集中在表面层的无机物质的高的热导率可以消散电晕产生的热量,减小了热击穿的危险,同时由于电晕放电作用在无机物上,而无机材料具有更好的耐电晕性和更高的耐受电晕产物腐蚀的能力。耐电晕聚酰亚胺薄膜中的无机相电晕老化后呈现更浓密的絮状团簇,无机-有机相界面间有很好的浸润性,而原始薄膜没有这一现象。研究了Dupont原始及耐电晕聚酰亚胺薄膜的介电谱特性、电导电流特性、退极化电流特性和热激电流特性,得出耐电晕薄膜的电老化阈值高于原始薄膜,且均随电晕老化场强的增加而下降。原始和耐电晕薄膜的载流子视在迁移率的变化范围分别为1.1×10-13m2/Vs-7.5×10-14m2/Vs和1.2×10-13m2/Vs-3.0×10-14m2/Vs,相应的陷阱深度变化范围分别为1.185eV-1.200eV和1.168eV-1.220eV。根据电导电流的温度特性得出,耐电晕薄膜的载流子活化能为0.76eV,原始薄膜为0.93eV。两种薄膜的热激电流峰值随极化场强增加而增加,原始薄膜的峰温基本不变,耐电晕薄膜略向高温移动。对热激电流曲线分峰处理,得出两种薄膜的活化能分别为0.65-0.91eV和0.60-0.90 eV。耐电晕薄膜中的浅陷阱,可能是薄膜耐电晕性提高的重要原因。研究了溶胶-凝胶法合成的含量分别为5wt%,10wt%,12.5wt%,15wt%和20wt%的纳米Al2O3复合聚酰亚胺薄膜的介电常数、介质损耗角正切与频更多还原

【Abstract】 The progress in nano-science and technology provided a new train of thought and a way for developing new materials and modifying the present materials. The appearance of nanodielectrics opened a new application field of the dielectrics. The electrical, thermal and mechanical properties of nanodielectrics were better than those of conventional ones. With the development of power electronics technology and new semiconductor devices, more and more AC frequency conversion adjustable-speed motors have been widely used especially after 1980’s. However, the life of the motor was only about one or two years due to partial discharge, what is more, the insulations in some motors were breakdown during the test running. Cooperating with ABB and Siemens, Dupont developed the corona-resistant polyimide film, the corona-resistant time of which could be up to 105 hours under 20kV/mm field, approaching the level of mica paper. The further research on the mechanism of corona resistance from the dielectric theory has not reported.The construction of Dupont corona-resistant polyimide film was analyzed by means of SEM and AFM, and the surface morphology of the original film and the corona- resistant film were compared with each other after aged. We found that Dupont corona-resistant film is three layers in construction and the two surface layers containing more Al-compound are inorganic-organic composite. The reason of the corona resistance of this film may be that the inorganic substance concentrating in the surface layers has higher heat conductivity, which can dissipate the heat produced by corona, and thus reduces the danger of thermal breakdown. Meanwhile, corona acts on the inorganic substance, which has good corona-resistance and ability to tolerate the corrosion of the corona products. After corona aging, the inorganic phase in the corona-resistant film appears flocculating cluster and infiltrated organic phase well. On the contrary, there is no such phenomenon taking place in original film.The investigation of the characteristics of dielectric spectrum, the conduction current, the depolarizing current and the thermally stimulated current of Dupont original and corona resistance films shows that the threshold of the corona-resistant film is higher than that of the original film and decreases with the increase of the更多还原