Metal Oxide Varistor (MOV) Specifications

We talked about MOV in one of our blog posts and the link is given below. In this article, we will touch the specifications of the MOV.

https://embeddeddesignblog.blogspot.com/2013/11/metal-oxide-varistor-mov.html

Below is the specification snapshot from the MOV datasheet which mentions about various performance parameters:

Maximum Allowable Voltage:

This is the maximum voltage below which Varistor can be used with minimum leakage. So, when we select a MOV, our DC voltage applied must be less than or equal to this voltage beyond which leakage starts. When we say low leakage here, it is in uA and is part of the specification mentioned in the datasheet.

Varistor Voltage:

This is the wide operating voltage specification of the Varistor. We can use the Varistor in the circuit but with some leakage. This leakage is more than the leakage seen at Maximum allowable Voltage.

Maximum Clamping Voltage:

Once the over voltage situation occurs, MOV has to start conducting and then clamp the voltage to a safe level. Clamping voltage is the maximum voltage clamped by the MOV

Peak Current:

Peak current is the maximum current specification of the MOV. This current passes through the MOV under clamping voltage.

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Below is a very important I-V curve, which details the current and voltage across the MOV.

The above graph clearly shows the dependency of the voltage on the current passing through the MOV. We can see from the graph that when the current is under Maximum Leakage current, the voltage is as per the operating voltage of the circuit. As the current increases from 1mA, the voltage across MOV increases till the clamping voltage.