Failure protection of varistor (2)

When the high power frequency transient overvoltage acts on the varistor, it may make the varistor short-circuit at the moment (low impedance short circuit), while the temperature safety tube is too late to fuse and may fire. In order to avoid this phenomenon, an impact resistance fuse (single frequency fuse may not be fused when aging failure) can be connected to each varistor. Also, the varistor can be used in series with the ceramic gas discharge tube, and the ceramic gas discharge tube is not guided in normal operation, and the varistor has no leakage current. It can greatly prolong the service life. When the surge is impacted by the surge, the ceramic gas discharge tube first penetrated and the surge voltage was limited by the varistor. The total residual pressure is both. And, slightly increased (tens of volts); after the impact of the past, due to the pressure sensitive resistor limiting the current, the discharge tube can not keep on and extinguish the arc and return to normal working state. When the varistor is short circuited, the ceramic gas discharge tube flows through a large power frequency current will also quickly fail, but its failure mode is the overwhelming majority. It's open, so it's not easy to cause a fire.