高能ZnO压敏电阻在能量脉冲下的动态老化

Degradation Due to Energy Pulse in High energy ZnO Varistors

研究了用于水轮发电机灭磁与过电压保护的高能ＺｎＯ压敏电阻在贮能电感释放的能量脉冲作用下的老化现象。能量脉冲可以分解为直流电场和能量两个分量。能量脉冲后，压敏电阻的特征电压、非线性系数和预击穿区Ｖ－Ａ特性都发生跌落，而且这种跌落随脉冲次数增加而增加；能量脉冲使压敏电阻发生非对称老化。高能ＺｎＯ压敏电阻在能量脉冲下的老化机理是发生在晶粒耗尽层中和富铋晶界层中的离子迁移使双Ｓｃｈｏｔｋｙ势垒降低。

The degradation phenomena due to the energy pulse in the high energy ZnO varistors used for deexcitation and overvoltage protection of hyreoelectric generator are investigated in this paper. The energy pulse,obtained by releasing the energy stored in an inductor,can be equivalent to the combination of the DC field component and the energy component. The characteristic voltages,nonlinear coefficient and pre breakdown V A characteristics will drop and the variations increase with the number of the applied energy pulse. The asymmetrical variations of the electric properties of the high energy ZnO varistors after the energy pulse arise from the deformation of the double Schottky barriers due to the ion migration occuring in the depletion layer and in the grain boundary.