MOV is what's inside a lot of small "surge supressors" in a sturcture having a multi-grain ceramic semiconductor.
It has a rather high resistance until the voltage gets over a threshold, at which time the resistance drops (but not to zero).
- Wide operating voltages ranging from 5Vrms to 1000Vrms (6Vdc to 1465Vdc).
- Fast response time of less than 25nS, instantly clamping the transient over voltage.
- High surge current handling capability.
- High energy absorption capability.
- Low clamping voltages, providing better surge protection
- Low capacitance values, providing digital switching circuitry protection.
- High insulation resistance, preventing electric arching to the adjacent devices or circuits.
- Transistor, Diode, IC, Thyristor or Triac semiconductor protection.
- Surge protection in consumer electronics.
- Surge protection in industrial electronics.
- Surge protection in electronic home appliances, gas and petroleum appliances.
- Relay and electromagnetic valve surge absorption.
The Prevention of Overvoltage
Varistor with high resistance allows only very small electrical current passing through.The current is so called leakage current.
When surge current happened, the resistance of varistor suddenly dropped to few ohm.
With such low resistance, it allows the surge current passing through and further protects other devices that parallel with Varistor. It is so called breakdown phenomena.