Can a varistor go bad?

The varistor, normally having a very high resistance, responds to the voltage spike by absorbing its energy with a very low resistance. This will also blow the equipment’s fuse but protect the expensive electronics. If the varistor is visibly burnt through or broken, it is bad; replace it.

Why is MOV burned?

We found that due to neutral disconnection, neutral reference point in board will increase rapidly which will cause a line to neutral voltage of more than 320V rms which is higher than normal condition of 230V. Since MOV used was rated for 300V rms AC voltage maximum, which result in MOV burnt issue.

How does MOV varistor work?

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.

Can you remove a varistor?

Just leave it open. Simply remove it untill you find a replacement.

What happens if a varistor fails?

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.

Can I remove varistor from circuit?

Metal-oxide varistors (MOVs) are the most widely used device for protecting sensitive electronics from damaging overvoltage transients. To date, most consider MOVs to be sacrificial devices, expected to disconnect (open) in the event of a failure. Unfortunately, this is not the case.

How do I know if my varistor is bad?

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 does varistor protect circuit?

Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.

Can MOV go bad?

Most surge protectors contain MOVs (Metal Oxide Varistors). After enough events, the MOV will fail and leave you with no protection. But an MOV can fail catastrophically if there is no current-limiting fuse in series with it. And if a current-limiting fuse blows, it will let a serious voltage peak go undamped.

How does a varistor fail?

Varistors need to absorb the energy deposited by temporary overvoltage, switching surges, or lightning impulses. That in turn has a direct relation to failure modes, which include electrical puncture, physical cracking, and thermal runaway. …