Technology & Computing

What is varistor used for?

By: Alfredo RicoUpdated: December 21, 2020

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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.

In this manner, how do I know if my varistor is bad?

If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown. Resolder the disconnected lead if the varistor's resistance reads good. If the varistor is blown, disconnect the remaining lead and solder a new varistor of the same rating in its place.

How does varistor protect circuit?

Therefore, when circuit protection from voltage surges is required, a varistor is used as a voltage protection device. When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.

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.

What happens when a varistor fails?

For an MOV to operate without failure or degradation it must quickly dissipate absorbed energy and return to its standby operating temperature. Degradation and catastrophic failures may occur if an MOV is subjected to transient surges beyond its rated values of energy and peak current.

Related

Do varistors have polarity?

However metal-oxide-varistors are symmetric by construction. Typically a layer of zinc-oxide is sandwiched between two metal plates. There is no polarity.

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. However, a capacitor cannot suppress voltage surges in the same way a varistor can.

What is the difference between varistor and thermistor?

is that varistor is an electronic component having a variable resistance; used to protect circuits against power surges while thermistor is a resistor whose resistance varies rapidly and predictably with temperature and as a result can be used to measure temperature.

What does a surge arrestor do?

A surge arrester is a protective device for limiting voltage on equipment by discharging or bypassing surge current. An arrester does not absorb lightning or stop lightning. It diverts the lightning, limits the voltage and protects the equipment installed in parallel.

What causes transient voltage?

Voltage Transients are defined as short duration surges of electrical energy and are the result of the sudden release of energy previously stored or induced by other means, such as heavy inductive loads or lightning. Random transients, on the other hand, are often caused by Lightning and Electrostatic Discharge (ESD).

What is Clamping Voltage in varistor?

This rated or clamping voltage is the voltage across the varistor measured with the specified DC current of 1mA. That is, the DC voltage level applied across its terminals that allows a current of 1mA to flow through the varistors resistive body which itself is dependant upon the materials used in its construction.

How do you select metal oxide varistor?

For example, selecting a MOV or silicon varistor for that matter, for voltage, its maximum continuous rms voltage rating should be just above the highest expected supply voltage, say 130 volts rms for a 120 volt supply, and 260 volts rms for a 230 volt supply.

What is MOV in electrical?

– A Metal Oxide Varistor (MOV) is a voltage suppression device that filters and clamps the transient in an electrical circuit. A Varistor is a Variable Resistor, sometimes referred to as Voltage Dependant Resistors (VDRs) by some manufacturers.

How do you calculate MOV?

This is the electrical energy that the MOV can safely absorb at least once before failing. You can calculate the energy by multiplying peak surge volts by amps, and then by seconds of time. For example, 1,000 volts x . 1 amps x .

What is clamping voltage?

Clamping voltage, also referred to as let through voltage or the Voltage Protection Rating (VPR), is the amount of voltage a surge protector permits to pass through it to the attached load (ex: a TV) during a surge event. The clamping voltage is 600V.

How do MOV surge protectors work?

In the most common type of surge protector, a component called a metal oxide varistor, or MOV, diverts the extra voltage. As soon as the extra current is diverted into the MOV and to ground, the voltage in the hot line returns to a normal level, so the MOV's resistance shoots up again.

What is a MOV surge protector?

A metal oxide varistor, or MOV, is an electronic component that protects equipment from voltage surges in a power line, such as from lightning strikes. Simple and inexpensive, the MOV absorbs the energy in a surge, preventing it from damaging other devices in a circuit.

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 work of rheostat?

A rheostat is a variable resistor which is used to control current. They are able to vary the resistance in a circuit without interruption. The construction is very similar to the construction of a potentiometers. It uses only two connections, even when 3 terminals (as in a potentiometer) are present.

What is a Metrosil?

Metrosil is used to limit the peak voltage developed by the current transformer (CT) under internal fault conditions to a value below the insulation level of the CT, relay and interconnecting leads.