What is a varistor 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.

What is a typical application of a VDR?

These VDRs are useful for a wide variety of applications that can include: Telephone and other communication line protection. Radio communication equipment transient suppression. Surge protector power strips.

How does MOV varistor work?

The main function of MOV is to work as a surge suppressor. When the voltage across the varistor is below the clamping voltage then varistor will not conduct. The main feature of this kind of varistor is response time because the voltage spikes are shorted in nanoseconds with the device.

What is a varistor test?

A varistor is an electronic component that protects expensive devices from harmful power surges, much like a shock absorber. This may blow the equipment’s fuse, but it will protect the expensive electronics. A varistor that’s received a strong electrical jolt may remain at low resistance and should be tested.

What is the symbol for a varistor?

The varistor circuit symbol can be seen to be very similar to that of a thermistor. It consists of the 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. This indicates the no-linear nature of the varistor.

How do you check if a varistor is working?

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 do you test a varistor?

How do you test for varistor? 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.

What can a leaded disk varistor be used for?

Varistors can be used as suppressors to protect devices and circuits from transient abnormal voltages including an ESD (electrostatic discharge) and a lightning surge. For protection from a relatively large surge current (100A to 25kA), leaded disk varistors and SMD disk varistors are suitable.

Why are varistors used in voltage clamping devices?

Metal oxide varistors are the most commonly used components that are used as voltage clamping devices to protect small or heavy devices from transient voltage surges. Since a metal oxide is used in its construction, the ability to absorb short voltage transients and the energy handling capabilities are extremely high.

What’s the maximum surge current a varistor can take?

The maximum surge current a varistor can take will depend on the width of transient pulse and number of pulse repetitions. Typical widths of transient pulse are in the range of 20 microseconds to 50 microseconds. There is a chance of overheating if the rated peak pulse current is insufficient.

What are metal oxide varistors and what are their applications?

To overcome the limitations of semiconductor based varistors like Silicon carbide varistors, the Metal Oxide Varistors (MOV) have been developed. Metal oxide varistor is a voltage dependent resistor. It is also a non linear device and provides very good transient voltage surge protection.