Views: 1 Author: Site Editor Publish Time: 2018-12-03 Origin: Site
The varistor has a high impedance relative to the protected electronic component. When a transient overvoltage occurs (beyond the voltage that the varistor can withstand), the varistor impedance becomes only a few ohms, causing a short circuit. The fuse is blown and the electronic components on the load are thus protected. Its main purposes are: lightning protection, overvoltage protection.
The varistor letters can be used for voltage regulation, overvoltage protection, high frequency circuits, lightning protection, arc extinguishing, noise cancellation, compensation, degaussing, high energy or high reliability. Although it can absorb a large amount of surge energy, it cannot withstand continuous currents above the milliamp level, and must be taken into account when used as overvoltage protection. For the selection of varistor, two parameters of nominal varistor voltage V1mA and flow capacity are generally selected.
1. The varistor voltage is the breakdown voltage. Refers to the voltage value at the specified current. In most cases, the voltage measured with a 1 mA DC current is applied to the varistor. The varistor voltage range of the product can range from 10-9000V. Can be selected according to specific needs.
2. The flow capacity is the peak value of the maximum pulse current. The specified inrush current waveform and the specified number of inrush currents, the maximum pulse current value when the varistor voltage does not change by more than ±10%. In order to extend the life of the device, the magnitude of the surge current absorbed by the varistor should be less than the maximum flux of the product given in the manual. However, starting from the protection effect, it is required that the selected flow rate is better. If the flow rate of the product at hand does not meet the requirements for use, several single varistors can be used in parallel. The varistor voltage after parallel connection is constant, and the flow rate is the sum of the values of the individual varistor. It is required that the volt-ampere characteristics of the varistor connected in parallel are as similar as possible, otherwise the shunting may be uneven and the varistor may be damaged.
