A few aspects about increasing the thermal stability of low voltage ZnO based varistors

ZnO based varistors are today frequently used for making state of the art surge arresters for all voltage levels, due to some advantages like a high nonlinearity coefficient and a high energy absorption capacity. Due to their thermal activated conduction, the heat dissipation inside that semiconductor device is crucial for its service. Heat dissipation study could be done only by modeling the thermal and electrical status of the varistor in case of some special and original configurations. The new configuration proposed in this paper consists in a disc varistor with an additional brass mass used for heat extraction and dissipation. This paper presents the finite-element model used for the direct control of heat dissipation, as well as some experimental results.