Degradation of Metal-Oxide Varistors by Steep Current Impulses

Metal-Oxide Varistors (MOV) are semiconductive ceramics with a highly non-linear voltage-current characteristic. The excellent clamping behaviour of this arrester material against fast surges is investigated experimentally in a very special circuit. In addition the changes of the most important characteristics of the material due to steep current impulses are measured. The main investigated parameter is the influence of the current steepness upon the AC power loss. Further parameters are the pulse polarity and the magnitude of the AC voltage. For certain effects a physical explanation will be given.