压敏电阻冲击老化过程中残压比变化的分析

Analysis on the Varying of ZnO Varistor's Residual Voltage Ratio During the Process of Impulse Degradation

残压比是衡量压敏电阻性能的一项重要指标,针对压敏电阻在冲击老化过程中残压比的变化问题,通过对压敏电阻样品进行8/20μs雷电流冲击老化试验,发现残压比在标称电流(In)冲击老化试验过程中呈现缓慢降低--缓慢增加--快速上升的变化趋势;根据双肖特基势垒理论及热老化理论分析,得出冲击过程中残压比的大小主要由晶界层状态所决定,残压比快速上升阶段是由于晶界层大量破坏的结论;提出了利用残压比变化率来衡量压敏电阻老化程度的方法,在实际应用中具有参考价值。

The Residual voltage ratio is an important index for ZnO varistor. In order to research the varying of ZnO varistor＇s residual voltage ratio during the process of impulse degradation, samples of ZnO Varistor are impacted by 8/20μs impulse current. Under the impact of In impulse current, It is found that the residual voltage ratio will first decrease slowly, and then increase slowly and finally increase sharply. Based on double Schottky barrier theory and thermal aging theory, the residual voltage ratio is determined by the state of grain boundaries; the sharply-increasing stage of residual voltage ratio is resulted from the destruction of grain boundaries. It is proposed that the change rate of residual voltage ratio can better estimate the degradation degree of ZnO varistor, which has a certain reference value in the practical application.