Varistor protected surge protectors

Varistor protection

— protection built on varistors — resistors that can sharply reduce resistance (from billions to tens of ohms) with increasing input voltage. Designed mainly for protection against short-term impulses: in such cases, excess energy is passed through the varistor and dissipated in the form of heat. Thus, varistor circuits are similar in purpose to lightning protection (see the relevant paragraph). However, on the one hand, they are easier to connect (they do not have such strict grounding requirements), on the other hand, they are somewhat less efficient: the varistor can absorb a relatively small amount of energy, after which it is turned off by thermal protection to avoid overheating.