What are varistors used for?

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.

Why would you put a resistor in a circuit?

In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

Why MOV is used?

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 is the function of voltage dependent resistor?

A varistor is a device with a non-linear volt-ampere characteristic. It is mainly used to clamp the voltage when the circuit is subjected to overvoltage and absorb excess current to protect sensitive devices. It is also called “Voltage-Dependent Resistor” abbreviated as “VDR”.

How do metal oxide varistors work?

When exposed to high transient voltage, the MOV clamps voltage to a safe level. A metal oxide varistor absorbs potentially destructive energy and dissipates it as heat, thus protecting vulnerable circuit components and preventing system damage. Varistors can absorb part of a surge.

What happens when 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.

What can be used as a resistor?

All electrically conductive materials are somewhat resistive, too. Because of this, even a good electrical conductor, such as metal wire, can be used as a resistor. Resistance can be adjusted by limiting how thick the wire is, and by increasing or decreasing the conductive path through the wire.

What does a resistor do to current?

Resistors let you choose how much current flows for a given voltage since you can think of wires as having no resistance (simplified). In short: Resistors limit the flow of electrons, reducing current. Voltage comes about by the potential energy difference across the resistor.

What is a MOV in electrical?

An MOV is a voltage dependent device which has an electrical behavior similar to back to back zener diodes. ▪ When exposed to high voltage transients, the MOV’s resistance. changes from a near open circuit to a very low value, thus clamping the transient voltage to a safe level.

Do varistors have polarity?

Does a varistor have polarity? In the case of metal oxide varistor, a zinc-oxide layer is basically sandwiched between two metal electrodes. As a result, there is no polarity.

How do you use varistor in a circuit?

As such varistors are used in sensitive electronic circuits to ensure that if the voltage does suddenly exceeds a predetermined value, the varistor will effectively become a short circuit to protect the circuit that it shunts from excessive voltage as they are able to withstand peak currents of hundreds of amperes.

What is the difference between fuse and varistor?

Unlike the fuse or circuit breaker which offers over-current protection, the varistor provides over-voltage protection by means of voltage-clamping in a similar way to the zener diode. In many ways the varistor looks similar in size and design to a capacitor and is often confused as being one.

What are the applications of a varistor?

Applications of Varistors. Protection of Electrical and Electronics Circuit: Varistors protect electrical and electronics circuit by allowing excessive current to pass through them. Varistors are connected parallel to the electrical or electronic component in the circuit.

What is the voltage of the varistor in the circuit?

The general fluctuation of the domestic power grid is 25\%. A varistor with the voltage of 470V to 620V should be selected. Selecting a varistor with a higher voltage can reduce the failure rate and prolong the service life, but the residual voltage is slightly increased.

What is the nonlinear behaviour of a varistor?

The resistance shows nonlinear behaviour with applied voltage. The varistors protect the circuit by allowing excess current to flow through them and prevent the circuit from getting damaged.The current- voltage characteristics of varistor also possess nonlinear characteristics.

What is the difference between an ordordinary resistor and a varistor?

Ordinary resistors obey Ohm’s law, while the voltage and current of the varistor have a special non-linear relationship. When the voltage at both ends of the varistor is lower than the nominal rated voltage, the resistance value of the varistor is close to infinite, and there is almost no current flowing through the inside of the varistor.