The varistor is usually connected in parallel in the circuit. When the voltage at both ends of the resistor changes, the short circuit will fuse the current and protect the whole circuit. The role of varistor is power supply overvoltage protection and voltage stability, today xiaobian to share some experience and methods of using varistor in work.

1, varistor voltage UN(U1mA) : usually in the varistor through 1mA DC current voltage to indicate whether the signal voltage, this voltage is called the varistor voltage UN. The symbol U1mA is also commonly used for varistor-sensitive voltage. The error range of varistor is generally ±10%. In test and practical application, the failure criterion of varistor is usually taken as 10% drop of varistor voltage from normal value.

2. Maximum continuous working voltage UC: refers to the maximum AC voltage (effective value)Uac or maximum DC voltage Udc that the varistor can withstand for a long time. Generally Uac≈ 0.64U1Ma, Udc≈ 0.83u1Ma.

3. Maximum clamping voltage (limiting voltage)VC: The maximum clamping voltage is the voltage present on the varistor when the specified 8/20μs wave IX(A) is applied.

4. Leakage current Il: the current that flows when the maximum DC voltage Udc is applied to the varistor. Leakage current is usually measured by applying a voltage of Udc=0.83U1mA to the varistor (sometimes 0.75U1mA). Generally, static leakage current Il≤20μA(also ≤10μA). In practice, the more concerned is not the size of the static leakage current value itself, but its stability, that is, the rate of change after impact test or under high temperature conditions. After impact test or under high temperature condition, the rate of change is not more than one times, it is considered stable.