How to choose a zinc oxide varistor?

The action clamping of the varistor is similar to the breakdown conduction mechanism of the semiconductor component, and its action delay is very small, generally in the order of ns. A varistor is a voltage-limiting protection device. Taking advantage of the nonlinear characteristics of the varistor, when the overvoltage occurs between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, so as to realize the protection of the subsequent circuit.

Zinc oxide varistor is a polycrystalline semiconductor ceramic component made of zinc oxide as the main body, doped with a variety of metal oxides, and made by a typical electronic ceramic process. The varistor has a symmetrical volt-ampere characteristic curve, and the current flowing through the MOV increases exponentially with the increase of the voltage at both ends of the MOV. In the actual application process, MOV is generally connected in parallel in the circuit, and when the circuit is working normally, it is in a high-impedance state and does not affect the normal operation of the circuit.

When the circuit has an abnormal transient overvoltage and reaches its on-voltage (varistor voltage), the MOV quickly changes from a high-impedance state to a low-impedance state, dissipates the instantaneous overcurrent caused by the abnormal transient overvoltage, and clamps the abnormal transient overvoltage within a safe level, so as to protect the subsequent circuit from the damage of abnormal transient overvoltage.

High surge absorption capacity, a variety of surge absorption capacity: standard, high surge, ultra-high surge, the physical size of the varistor determines its surge absorption capacity;

The response speed is ns-level.

The voltage range is 18V to 1800V, and the voltage accuracy is usually 10%, which meets the needs of low voltage to high voltage applications;

MOVs are all plug-in devices, with various sizes, Dongwo Electronics can provide MOVs with a diameter of 5mm-53mm;

The flow rate of a single unit can reach several hundred amperes to tens of thousands of amperes.

Zinc oxide varistor disadvantages:

An aging component, often used in series with a gas discharge tube when protecting a high-power power supply port, slows down aging and prolongs service life;

The parasitic capacitance is large, which will cause high-frequency signal transmission distortion in high-frequency signal systems;

A varistor is a metal-oxide-semiconductor nonlinear resistor with zinc oxide as the main component.

The object of weighing is "analysis of pure Bi2O3, MnCl2 4H2O, CoCl2 6H2O, Cr(NO3)3 7H2O and Ba(NO3)2", and the ratio requirement of each substance is that the mixed substance is "Bi2O3:Mno2:CO2O3:".

ba（no3）2：cr2o3=：17%：：

3%", which is actually the preparation of "72% Bi2O3+" by "analyzing pure Bi2O3, MnCl2 4H2O, CoCl2 6H2O, Cr(No3)3 7H2O and Ba(No3)2".

MnCl2 4H2O and CoCl2 6H2O both contain chlorine, so there are chloride ions in the solution, and NH4HCO3 NH3 H2O is used to remove chloride ions.

As for the pH value and concentration of the H4HCO3 NH3 H2O buffer solution, it does not require it, as long as the pH value of the solution that comes out of your final solution is OK.

The most important parameters for the selection of varistors are: maximum allowable voltage, maximum clamping voltage, and inrush current that can be withstanded.

First of all, it should be ensured that the maximum allowable voltage of the varistor is greater than the maximum value of the output voltage of the power supply; Secondly, it should be ensured that the maximum clamping voltage will not exceed the maximum inrush voltage allowed by the subsequent circuit; Finally, it should be ensured that the inrush current flowing through the varistor does not exceed the inrush current that it can withstand.

Other parameters, such as the rated power and the maximum energy pulse that can be tolerated, can be determined by simple calculations or experiments.

The parameters of zinc oxide varistor are Zhixu electronics, and you can also do samples.