【作者】 曹开江；

【导师】 吴广宁；

【作者基本信息】 西南交通大学 ， 高电压与绝缘技术， 2013， 博士

【摘要】 变频调速牵引电机作为高速动车的九大关键技术之一,其定子绝缘系统工作在逆变器输出的PWM高频方波脉冲电压下,是保障高速动车安全运行的关键。变频牵引电机作为高速动车的核心部件,其绝缘系统是电机的薄弱部位,承受PWM高频脉冲的持续冲击。牵引电机正在向高功率、体积小、质量轻、可靠性越来越高的方向发展,电机的绝缘系统将工作在更加严酷的电气环境下。因此,研究牵引电机定子绕组绝缘的击穿和寿命特性,分析高频方波电压下的放电特性及其对绝缘寿命的影响,探寻高频方波脉冲下的绝缘老化特性及表征参量,将推进高频方波脉冲电压下绝缘破坏理论的发展,学术价值和工程意义重大。针对牵引电机定子绕组匝间绝缘开展试验,研究了绝缘的击穿和加速老化寿命,分析了绝缘的击穿行为,发现了高频脉冲电压下绝缘的电压-重复率-上升时间联合寿命模型。结果表明：电击穿过程中电子从电场中得到的能量大于损失给晶格振动的能量,电导进入不稳定阶段,导致绝缘的迅速破坏；纳米颗粒的添加改善了聚合物的耐电树枝化能力；脉冲电压、重复率和上升时间的寿命特性都呈现为幂函数关系。采用高频高压脉冲下的局部放电检测系统,测试分析了不同脉冲参数下绞线对、电磁线以及绝缘材料的放电参量,讨论了空间电荷对放电以及寿命的作用机制。结果表明：随着脉冲重复率和电压上升率的升高,局部放电活动加剧,放电向方波脉冲的零点位置移动；空间电荷在脉冲极性翻转时气隙场强增大,电荷的存储效应增强了放电活动；纳米颗粒的添加改善了材料的电荷迁移能力,降低了材料局部场强畸变和局部放电活动。基于高频高压绝缘老化试验系统,研究了高频方波脉冲下绝缘的老化特性及表征,测试分析了不同老化时间下薄膜材料的表面形貌、剩余击穿场强和空间电荷分布特性,阐述了空间电荷对绝缘老化的影响,探索了表征绝缘老化程度的放电统计参量。结果表明：纳米粒子的添加降低了局部放电对材料的老化作用,纳米复合薄膜的剩余击穿场强下降较少；平均放电量的偏斜度可以预测绝缘的剩余寿命时间；脉冲重复率的增加、上升时间的缩短以及老化时间的增长都将导致空间电荷注入量增加,高能量热电子的产生和复合加速了绝缘老化进程。更多还原

【Abstract】 High-speed railway is built rapidly in recent years. Inverter-fed traction motors are employed for electric-multiple-units (EMUs) and are one of nine key techniques for EMUs, whose insulation is subjected to Pulse Width Modulated (PWM) impulse voltage. Insulation system is weak part of motor, and it is the key of secure running for EMUs. Higher power, smaller volume and lighter, as well as more reliable is direction of future traction motor. So insulation system of motor should be improved to meet the need of future motor. The thesis is to promote insulation aging and breakdown mechanism under high frequency impulse. Insulation breakdown and its life law, partial discharge (PD) activity and its effect on life under high frequency impulse, insulation aging and its characterization were investigated. It has important academic value and project significance.For magnet wires used in the stator coils of traction motor, electrical breakdown and electrical tree breakdown, meanwhile combining with scanning electron microscopy (SEM) and energy spectrum were analyzed, and the corresponding breakdown mechanisms were studied. Insulation failure time of magnet wires was tested under different voltage amplitude, impulse frequency and impulse rise time. The results show that during the process of electrical breakdown, when energy of electron received from electric field is higher than that transferred to the crystal lattice of polymer, conductance will become unstable. As a result, insulation was breakdown very quickly. During the process of electrical tree breakdown, tree branch resistance of polymer was enhanced because of nano particles. Life models of voltage, frequency, and rise time are all accord with power function.PD test system under high impulse voltage and high frequency was adopted. PD characteristics of twisted pair, magnet wire and polyimide film specimens were tested. PD activities, including partial discharge inception voltage (PDIV), PD parameters (mean discharge quantity, discharge number and phase resolved PD pattern) were analyzed. Relation between space charge and PD was discussed, and effect of PD on insulation life was investigated. The results show that PD activities would be more serious with increase of frequency and shortness of rise time, and move to the zero of impulse voltage. When polarity of impulse is reversed, electric field of cavity is enhanced because of space charge. Memory effect of space charge has great impact on PD activities. Diffusion ability of polymer is improved because of nano particles, which reduces the distortion of local electric field. So PD activity is weakened.Testing of electrical aging was adopted, and insulation aging characteristic was investigated. The destroy instance of films’ surface, residual insulation strength as well as space charge distribution of polyimide films were tested. The effect of space charge on insulation aging was discussed, and relation between PD parameters and aging time was researched. The result shows that reduce of residual insulation strength for nanocomposite film is lower, because accession of nano particles weakens the effect of PD on aging action for polymer. There is relationship between skewness of mean discharge quantity and aging time, and insulation condition could be judged by skewness of mean discharge quantity. More charges were injected into the film, with increase of frequency, shortness of rise time and increase of aging time. Free radical chain reaction of polymer will be induced by hot electron, which would accelerate the insulation aging process.更多还原