The capacitive current and conduction current of zinc oxide varistor ceramic materials for nanosecond pulse electronic breakdown

ZnO varistors are employed to protect for the electric circuits of information system, control system and high voltage engineering. Many studies on the pulse response of ZnO varistors used pulse power supplies or spark-gap more pulse power to provide electrical pulse excitation. The test system is designed to study the pulse response of ZnO varistor ceramics at DC bias. Both capacitive current i_C and conduction current i_R is clearly observed in the ultrafast electric current pulse output by ZnO varistors. The test results can be analyzed by using the switching characteristics of PCSS's and the conduction mechanisms of ZnO varistor ceramics. In the linear mode of SI-GaAs PCSS's, the composite electric pulse with capacitance current i_C and conduction current i_R can be obtained when the ZnO grain boundary is broken down. Because it needs to take some time to break down ZnO grain boundaries, and then, the capacity of grain boundaries decays rapid and the varistors sends out a conductance current, there is a certain delay between i_R and i_C which is observed clearly. These ultrafast pulse response characteristics of ZnO varistor ceramics provide an experimental data for the rationality of the theory of ZnO grain boundary.