The voltage and current of the zinc oxide varistor are in a special nonlinear relationship.When the voltage across the voltage equals or exceeds its sensitivity,The resistance will be from infinity, quickly reduced, similar to the short circuit,Blown circuit pre-fuse.To achieve the purpose of protecting the circuit after the class.For a small current, high voltage pulse,Because it is equivalent to short circuit,So the high pulse was bypassed by the varistor,When the high voltage has passed,His resistance and restore to infinity,Thus protecting the post-stage circuit,Not being hit by high voltage or high pulse.

When the voltage across the varistor is slightly higher than the nominal rated voltage,Varistor will rapidly breakdown conduction,And from the high impedance state into a low resistance state,Working current also increased dramatically.When the voltage at both ends is lower than the nominal rated voltage,Varistor can be restored to high impedance state.When the voltage across the varistor exceeds its maximum limit voltage,The varistor will be completely damaged by the breakdown,Can not be self-recovery.