高导热氮化铝/环氧树脂复合材料的高频沿面放电特性

High Frequency Surface Discharge Characteristics of Aluminum Nitride/Epoxy Resin Composites With High Thermal Conductivity

环氧树脂(epoxy resin,EP)因其优异的绝缘性能被用作高频变压器的主绝缘材料,但受限于材料的散热能力在强电-热耦合应力下容易发生沿面放电,采用三维导热网络法进行改性是有效的解决方案。该文采用硅烷偶联剂接枝改性氮化铝颗粒,分别制备填料随机分布与含导热网络的氮化铝/环氧树脂复合材料,与纯环氧树脂同时进行高频沿面绝缘特性与放电过程温度分布测试。实验结果表明,含氮化铝三维导热网络的EP复合材料可在提升高频绝缘性能的同时抑制材料表面的高频致热效应,在10kV/10kHz高频正弦电压下,相比于纯环氧树脂,总放电幅值从81.47V下降到了24.01V,放电后材料表面最大温升由145.9℃下降至117.6℃。进一步给出环氧复合材料的导热-绝缘协同提升机理:(1)导热网络结构在提供规整的热流传输通道的同时,抑制了填料与基体界面的电场畸变;(2)导热网络结构能显著提升表面浅陷阱密度,减少电荷脱陷的势垒,增强对放电的抑制作用;(3)在高频沿面放电过程中,f/K-AlN/EP自身导热率提升迅速,电导率提升缓慢,消散热量与抑制放电的趋势提升显著,提升了高频沿面放电寿命。

Epoxy resin(EP)is used as the main insulation material of high-frequency transformer because of its excellent insulation performance.Due to the heat dissipation ability of the material,it is easy to discharge along the surface under the strong electric-thermal coupling stress.It is an effective solution to use three-dimensional heat conduction network method for modification.In this paper,aluminum nitride/epoxy resin composites with randomly distributed fillers and heat conduction skeleton are prepared by grafting modified aluminum nitride particles with silane coupling agent.The surface insulation characteristics and temperature distribution during discharge are tested at high frequency with pure epoxy resin.The experimental results show that the EP composite material containing aluminum nitride three-dimensional thermal conductivity network can improve the high-frequency insulation performance while suppressing the high-frequency heating effect on the material surface.Under a high-frequency sinusoidal voltage of 10 kV/10 kHz,compared to pure epoxy resin,the total discharge amplitude decreases from 81.47 V to 24.01 V,and the maximum temperature rise on the material surface after discharge decreases from 251.9℃to 117.6℃.The mechanism of thermal conduction-insulation synergetic enhancement of epoxy composites is further presented.First,the thermal conduction network structure can suppress the electric field distortion at the interface between the filler and the matrix by reducing the spacing between the fillers while providing a regular heat flow transmission channel.Then,the heat conduction network structure can significantly increase the density of shallow traps on the surface,reduce the potential barrier of charge trap,and thus enhance the inhibition of discharge.Next,in the process of high-frequency surface discharge,the thermal conductivity of f/K-AlN/EP increases rapidly,the conductivity increases slowly,and the trend of dissipating heat and suppressing discharge increases significantly,which improves the life of high-frequency surface discharge.