电工技术学报  2023, Vol. 38 Issue (15): 3999-4009    DOI: 10.19595/j.cnki.1000-6753.tces.221798
高电压与放电等离子体 |
高压器件封装用有机硅凝胶内气泡对其正极性方波电压下放电特性的影响
李学宝, 刘相辰, 刘思佳, 赵志斌, 崔翔
新能源电力系统全国重点实验室(华北电力大学) 北京 102206
Influence of Bubbles on the Discharge Characteristics of Silicone Gel for High Voltage Module Encapsulation under Positive Square Wave Voltage
Li Xuebao, Liu Xiangchen, Liu Sijia, Zhao Zhibin, Cui Xiang
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China
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摘要 有机硅凝胶内气泡缺陷是高压IGBT器件封装的绝缘薄弱环节。该文针对有机硅凝胶内气泡缺陷对放电特性的影响,制备了指定位置含有气泡的有机硅凝胶实验样品,提出了有机硅凝胶内部气泡含量的量化方法,面向器件运行条件下所承受的正极性重复方波电压工况,建立了基于局部放电电流脉冲测量方法的有机硅凝胶局部放电特性实验平台,提出了方波电压下放电电流脉冲的准确测量与提取的方法,通过实验获得了有机硅凝胶内气泡含量对局部放电分布特性及电流脉冲波形参数的影响规律,并给出了气泡对有机硅凝胶局部放电特性的影响机理的定性解释。结果表明:正极性重复方波电压下,有机硅凝胶的局部放电起始电压与熄灭电压均随气泡含量的增加而显著下降,反向放电比例随气泡含量的增加而增加,脉冲上升时间、下降时间随气泡含量的增加而减小。该文成果可为IGBT器件有机硅凝胶灌封工艺的改进提供指导,并为有机硅凝胶气泡含量检测奠定基础。
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李学宝
刘相辰
刘思佳
赵志斌
崔翔
关键词 IGBT器件绝缘有机硅凝胶气泡正极性重复方波电压局部放电    
Abstract:With the increasing voltage level of high-voltage IGBT modules, the package insulation of modules requires higher reliability. Therefore, the silicone gel with excellent insulation performance and low elastic modulus is widely used in the packaging of high-voltage IGBT modules. However, the bubble defect in silicone gel is the weak insulation link of package insulation. In this paper, the effect of bubble defect on the discharge characteristics of silicone gel under positive square wave voltage is investigated.
Firstly, the needle plate electrode structure is selected to form a local high field area to prevent the direct breakdown of the sample. The silicone gel samples containing bubbles in the specified position are prepared by layered potting. By analyzing the area of bright white spots in the high-definition images of the samples taken by the microscope, the amount of bubbles in the samples is estimated, and the content of bubbles in the prepared samples is determined to be 0%, 32%, 55%, and 74%, respectively. An experimental platform for partial discharge characteristics of silicone gel based on the partial discharge current pulse measurement method is established for the positive repeated square wave voltage consistent with the module operation condition.
Secondly, partial discharge experiments with different bubble contents are carried out under positive repeated square wave voltage. The statistical characteristics of PDIV and PDEV of each sample are analyzed by Weibull distribution. It is found that with the increase of bubble content, the partial discharge inception voltage(PDIV) and partial discharge extinction voltage (PDEV) of silicone gel samples are significantly decreased, especially the PDIV and PDEV of 74% bubble content samples are decreased by 42% and 46%, respectively.
Thirdly, a method to extract the discharge current pulse from the displacement current is proposed, and the obtained discharge current pulse has no distortion and no high-frequency noise. By analyzing the discharge pulses of samples with different bubble content for at least 50 cycles, it is found that with the increase of bubble content in silicone gel from 0% to 74%, the charge amount of a single local discharge in the sample shows an overall increasing trend, the proportion of forward discharge decreases from 55% to 37%, the rising and falling rate of the pulse increase by 3~5 times, and the rise time and fall time of the pulse decrease about 50%.
Finally, the discharge process with air bubbles in the silicone gel and the mechanical explanation of the effect of air bubbles on the discharge characteristics are analyzed. The simulation results show that the field strength in the bubble is larger than that in the silicone gel under the square wave voltage, while the breakdown field strength of the air is smaller. Therefore, the bubble is more prone to discharge than the silicone gel. In addition, part of the gas molecules will diffuse to the high field strength region through the silicone oil, which will also reduce the overall insulation strength of the silicone gel. In the process of partial discharge development, the electric tree inside the silicone gel will pass through the bubble, and the air components will enter the electric tree airway to participate in the discharge process, resulting in the improvement of the carrier mobility inside the electric tree airway, and then lead to the change of the partial discharge pulse waveform. The results of this paper can guide the improvement of silicone gel encapsulation technology and lay a foundation for the detection of bubble amounts in silicone gel.
Key wordsIGBT module insulation    silicone gel    void    positive repetitive square wave voltage    partial discharge   
收稿日期: 2022-09-23     
PACS: TM211  
基金资助:国家电网有限公司总部科技项目资助(5500-202299490A-2-0-KJ)
通讯作者: 李学宝 男,1988年生,副教授,博士生导师,研究方向为高压大功率电力电子器件封装。E-mail:lxb08357x@ncepu.edu.cn   
作者简介: 刘相辰 男,1997年生,硕士研究生,研究方向为高压大功率电力电子器件绝缘。E-mail:120202201087@ncepu.edu.cn
引用本文:   
李学宝, 刘相辰, 刘思佳, 赵志斌, 崔翔. 高压器件封装用有机硅凝胶内气泡对其正极性方波电压下放电特性的影响[J]. 电工技术学报, 2023, 38(15): 3999-4009. Li Xuebao, Liu Xiangchen, Liu Sijia, Zhao Zhibin, Cui Xiang. Influence of Bubbles on the Discharge Characteristics of Silicone Gel for High Voltage Module Encapsulation under Positive Square Wave Voltage. Transactions of China Electrotechnical Society, 2023, 38(15): 3999-4009.
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