DCF type safety ceramic capacitor 103M
Parameters to know in circuit design
The varistor is often connected in parallel in the circuit. When the voltage across the resistor changes, the resistor short-circuits fuse the current fuse to protect the entire circuit. The role of varistor is power supply overvoltage protection and voltage regulation. Today, Xiaobian will share with you some experience and methods of using varistor in work.
1. Varistor voltage UN (U1mA): Usually, the voltage when 1mA DC current passes through the varistor is used to indicate whether it is turned on or not. This voltage is called the varistor voltage UN. The varistor voltage is also commonly represented by the symbol U1mA. The error range of the varistor voltage is generally ±10%. In the test and actual use, the varistor voltage is usually reduced by 10% from the normal value as the criterion for the failure of the varistor.
2. The maximum continuous working voltage UC: refers to the maximum AC voltage (effective value) Uac or the 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 value refers to the voltage present on the varistor when the specified 8/20μs wave impulse current IX(A) is applied to the varistor.
4. Leakage current Il: the current flowing when the maximum DC voltage Udc is applied to the varistor. When measuring leakage current, a voltage of Udc=0.83U1mA is usually added to the varistor (sometimes 0.75U1mA is also used). Generally, the static leakage current Il is required to be ≤20μA (there are also requirements of ≤10μA). In actual use, what is more concerned is not the size of the static leakage current value itself, but its stability, that is, the rate of change after the impact test or under high temperature conditions. After the impact test or under high temperature conditions, its rate of change does not more than d
