The Working Principle and Selection Criteria of Varistor

Sep. 13, 2021

In the electronic market, we can see various types of varistors, the sizes of Φ5, Φ7, Φ10, Φ14, Φ25, Φ32, etc. Varistors can be used for lightning protection and circuit protection in different circuits. This article will help you to understand the working principle, functions and selection criteria of varistors.

The Working Principle and Selection Criteria of Varistor

Overview of varistor:

Varistor is a resistor device with non-linear volt-ampere characteristics. It is mainly used for voltage clamping when the circuit is subjected to overvoltage and absorbing excess current to protect sensitive devices.

The working principle of varistor:

Varistor is a voltage-limiting protection device. Because of the non-linear characteristics of the varistor, when an overvoltage occurs between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby fulfilling the goal of protecting the subsequent circuit. The main parameters of varistor are: varistor voltage, current capacity, junction capacitance, response time, etc.

The role of varistor:

Even when the current flowing through the varistor increases sharply, there will be little impact on other circuits, therefore a varistor can reduce the impact of overvoltage on subsequent sensitive circuits. Using this function, the abnormal overvoltage that often appears in the circuit can be suppressed, and the circuit can be protected from overvoltage damage.

The selection criteria for varistors are as follows:

1. VDR is strictly prohibited to be installed close to heating or combustible components - a gap greater than 3mm should be guaranteed.

2. If the varistor is connected between the live part of the device and the metal shell, measures must be taken to avoid electric shock.

3. The varistor should avoid working in an environment of high temperature and high humidity such as sunlight, wind, rain, water vapor, sand dust, salt dew, and harmful gases. When necessary, use a protective box for protection.

4. In the actual application process, it is strictly prohibited to clean the varistor with solvents such as acetone, so as not to damage the epoxy resin of the VDR package.

5. The storage temperature of the varistor should be below 40 degrees Celsius, and the relative humidity should be less than 75%RH.

6. When the surge current repeatedly occurs, the peak value of the surge current and the surge energy of the varistor cannot exceed the provisions of the pulse duration characteristics.

The above content is the principle, function and selection criteria of varistors. Hopefully the content of this article can help you understand varistors better. Dongguan Zhixu Electronic Co., Ltd. (also JYH HSU(JEC)) have complete varistor models with guaranteed quality. JEC factories has passed ISO9001:2015 quality management system certification; JEC safety capacitors (X and Y capacitors) and varistors have passed national certifications of the main industrial powers in the world; JEC ceramic capacitors, film capacitors and super capacitors are in compliance with environmental protection indicators. If you have technical questions or need samples, welcome to contact us.

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