The prominent failure mode for the MOV is sustained overvoltage. Under these conditions, the MOV begins to conduct power frequency (50 Hz to 60 Hz) current. The MOV ultimately reaches its maximum energy capacity and enters thermal runaway.

What happens when MOV fails?

The prominent failure mode for the MOV is sustained overvoltage. Under these conditions, the MOV begins to conduct power frequency (50 Hz to 60 Hz) current. The MOV ultimately reaches its maximum energy capacity and enters thermal runaway.

How do you test an MOV?

To test a MOV, apply a high voltage with a current limiting resistor in series (1M ohm?). The MOV should conduct and you them measure the voltage across it. Checking the actual voltage with the spec. voltage should indicate as to its possible use.

What is the working principle of MOV?

An MOV is a voltage dependent device which has an electrical behavior similar to back to back zener diodes. changes from a near open circuit to a very low value, thus clamping the transient voltage to a safe level. pulse is absorbed by the Varistor, thereby protecting vulnerable circuit components.

How many types of MOV are there?

There are two main varistor variants: Ceramic / metal oxide varistor: This form of varistor is the most widely used and it is the form that is often referred to when the term varistor is stated. The varistor is bidirectional and is based around a ceramic or metal oxide.

How do I check my MOV varistor?

Turn the multimeter on and set its function knob to read resistance. Touch the meter probe tips to the MOV’s leads and measure its resistance. If it has a resistance much under 100 ohms, it has blown.

How do I read varistor code?

Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.

How do I know if my varistor is bad?

How does a varistor fail?

Under different current conditions, failure modes include electrical puncture (see Figure 4), physical cracking (see Figure 5), and thermal runaway. Cracking happens because varistors are basically a ceramic material, and hitting them with a sharp high-amplitude surge is like hitting a dinner plate with a hammer.

What happens when a varistor fails?

How do I select a MOV varistor?

The first step of choosing a MOV is determining the continuous working voltage that will be provided across the varistor, you have to choose the varistor with maximum AC or DC voltage that matches or slightly higher than the applied voltage.

What is MOV component?

A Metal Oxide Varistor (MOV) is a protection component used in power supply circuits that is powered directly from AC mains. It is used to protect the circuit from high voltage spikes by varying its resistance.

Can I replace a varistor with a capacitor?

You can replace it with a new one provided it is for the same voltage levels that it triggers. This AC and DC voltage ratings are the important parts and then the energy capacity. Energy cap. is not a major issue in Computer PSUs since the usually use a small varistor there.