What is a varistor and how does it work?

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. The term is only used for non-ohmic varying resistors.

Hereof, 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.

Beside above, 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.

Consequently, what happens when a varistor fails?

A. When subjected to stresses above its ratings, an MOV can fail as a short circuit. If applied conditions significantly exceed the energy rating of the device, and current is not limited, the MOV may be completely destroyed.

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.

Do varistors have polarity?

There is no polarity. So you can mount MOVs in any direction. Other kinds of TVS, such as unipolar TVS diodes do have polarity, and it is typically indicated with a ring, like normal diodes.

How do varistors work?

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered. The name varistor is a portmanteau of varying resistor.

What is the use of varistor?

Varistors, also called metal-oxide varistors (MOVs), are used to protect sensitive circuits from a variety of overvoltage conditions. Essentially, these voltage-dependent, nonlinear devices have electrical characteristics similar to back-to- back Zener diodes.

What is clamping voltage of MOV?

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.

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 MOV do in an electrical circuit?

– 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.

Should a resistor have continuity?

The continuity range usually has a certain resistance threshold in which it considers a wire to be closed. If your resistor is of greater resistance than the threshold on your meter, then even though current can flow through it, the meter will not register continuity.

How do I test a 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. Desolder and remove the remaining lead and remove the MOV from the equipment.

What is voltage divider rule?

The voltage division rule (voltage divider) is a simple rule which can be used in solving circuits to simplify the solution. Voltage Division Rule: The voltage is divided between two series resistors in direct proportion to their resistance.

What is MOV surge protection?

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.

What are transient voltages?

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.

What is Znr?

ZNR stands for Zinc-oxide non-linear resistor, also commonly known as metal oxide varistor (MOV). Panasonic invented the ZNR surge absorber in 1968 and is a pioneer in the use of zinc oxide as a surge absorber.

What do you mean by LDR?

What is an LDR (Light Dependent Resistor)? An LDR is a component that has a (variable) resistance that changes with the light intensity that falls upon it. This allows them to be used in light sensing circuits. A typical LDR. LDR Circuit Symbol.

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. When the voltage is correct, an MOV does nothing. When voltage is too high, an MOV can conduct a lot of current to eliminate the extra voltage.

What is the full form of MOV?

Metal-Oxide Varistor

Which of the following circuit conditions does a metal oxide varistor MOV protect against?

The Metal Oxide Varistor is designed to protect various types of electronic devices and semiconductor elements from switching and induced lightning surges. When exposed to high transient voltage, the MOV clamps voltage to a safe level.