Polarization absorption currents and conduction response characteristics of zinc oxide varistors

The absorption currents and conduction response characteristics of zinc oxide varistors were measured with step voltage pulses of different amplitude, and a series resistance was used to stimulate the ZnO grain resistance of zinc oxide varistors. Based on an analysis of the experimental results, three kinds of absorption current were found, and an equivalent circuit describing the electrical properties of zinc oxide varistors was developed. It is deduced that conduction response time results from the equivalent capacitance of the grain boundary, and there is a close relation between the conduction delay phenomenon and the polarization absorption current. The larger the ZnO grain resistivity the shorter is the conduction response time