Metal Oxide Varistor

September 19, 2024 Post a Comment

Metal oxide varistor

Metal Oxide Varistors and Multi-Layered Varistors Therefore, MOVs are typically used for the suppression of lightning and other high energy transients found in industrial or AC line applications. Additionally, MOVs are used in DC circuits such as low voltage power supplies and automobile applications.

What does a MOV do in an electrical circuit?

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.

What happens when 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.

What is the meaning of metal oxide varistor?

Glossary Term: Metal Oxide Varistor Definition. A Metal Oxide Varistor (MOV, or surge-suppressor) is a discrete electronic component that diverts excessive voltage to the ground and/or neutral lines.

Why do you need a varistor?

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. A capacitor may be installed across the signal lines. However, this capacitor cannot suppress voltage surges.

What is the working principle of varistor?

Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered.

Why do we need MOV?

Hence MOVs are normally used in parallel with a fuse, to protect circuits from high voltage spikes. In this article, we will learn more about MOV Working and how to use it in your designs to protect your circuits from voltage spikes.

Does a varistor have polarity?

Varistor (Variable resistor) is a nonlinear resistive element of the voltage dependence that resistance changes with applied voltage. Varistor is equivalent with Zener diode of two series connection. Therefore, do not have polarity.

How does varistor protect circuit?

When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit. When the voltage surge does not exceed the varistor voltage, the varistor works as a capacitor.

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.

Do varistors fail open or short?

Varistors short circuit when an overage in potential is applied to it.

Why does a varistor burn out?

The surge energy is too large and exceeds the absorbed power; 8, the pressure is not enough; 9, current and surge are too large and so on. The safety of the use of varistors has always been a problem that needs attention.

What is the difference between resistor and varistor?

A varistor is a voltage dependent resistor (VDR). The resistance of a varistor is variable and depends on the voltage applied. The word is composed of parts of the words “variable resistor”. Their resistance decreases when the voltage increases.

Is metal oxide varistor a resistor?

The Metal Oxide Varistor or MOV for short, is a voltage dependant resistor in which the resistance material is a metallic oxide, primarily zinc oxide (ZnO) pressed into a ceramic like material.

What is the use of varistor in power supply?

A disk varistor is used for surge protection. When power is supplied from an alternator to a battery, disconnection of a battery line generates a large surge voltage. The varistor bypasses the surge voltage to protect an ECU and others.

How does a metal oxide varistor fail?

This failure mode can be caused by long-duration overvoltage, such as switching from a reactive load or thermal runaway of the MOV connected to the ac mains. Open circuit failures are possible if an MOV is operated at steady state conditions above its voltage rating.

How do I choose a varistor?

Choose a varistor with an energy absorption rating that equals or slightly exceeds the energy values associated with the event the circuit may experience. If, however, the transient voltage is due to an external event, the magnitude of the source energy is unknown.

Can you remove a varistor?

Just leave it open. Simply remove it untill you find a replacement. The circuit will work without it.

What is the symbol of varistor?

Varistor symbol The symbol of a varistor circuit is very similar to that of a thermistor. It consists of a basic resistor symbol of a rectangle with a diagonal line through it that has a small added section parallel to the body of the resistor symbol which indicates the nonlinear nature of the varistor.

Is a MOV a varistor?

MOV refers to the metal oxide varistors. MOV has a symmetrical volt-ampere characteristic curve (as shown in Figure 1). When MOV is applied, it is generally connected in parallel in the circuits.