First, the protection principle of zov varistor A zov varistor is a voltage-limiting protection device. Using the non-linear characteristics of a varistor, when an excessively high voltage appears between the two poles of the zov varistor, the varistor can clamp the voltage to a relatively fixed value, thereby Achieve protection for the subsequent circuit.
Second, the cause analysis of zov varistor damage
The failure mode of the zov varistor is mainly short circuit, but the short circuit itself does not cause damage to the zov varistor, because the resistance is at the positive and negative inlets of the power supply; the insurance is not damaged, which proves that the damage of the varistor is not a short circuit or overcurrent. The cause may be that the surge energy is too large, and the zov varistor is burned beyond the absorbed power; when the overcurrent passed is too large, the valve disc may be burst and open.
So, what are the causes of damage to the zov varistor?
1. Over-voltage protection times;
2. Surrounding working temperature;
3. Whether the varistor is squeezed;
4. Whether it has passed quality certification;
5. The surge energy is too large to exceed the absorbed power;
6, the pressure is not enough;
7. Excessive current and surge, etc.
In addition, the zov varistor has a short service life and its performance will decrease after repeated impacts. Therefore, after long-term use, the lightning arrester composed of zov varistor must pay attention to maintenance and replacement.