How do you identify 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.

How do you read numbers on 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. If it reads very low resistance, the varistor is blown.

How do you select a metal oxide varistor?

The first step of choosing a MOV is determining the continuous working voltage that will be provided across the varistor, you have to choose the varistor with maximum AC or DC voltage that matches or slightly higher than the applied voltage.

What are the numbers on varistor?

They have peak current ratings from about 20 to 500 amperes, and peak energy ratings from 0.05 to 2.5 joules.

What is MOV used for?

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.

How do I select a varistor?

Select a model to provide the required voltage-clamping characteristic A final consideration is to choose the appropriate package style to suit the application. Consider the maximum continuous voltage that will be applied to the varistor including any high line conditions (i.e., 110% or more of nominal voltage).

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.

How are varistors rated?

The energy rating is determined by volume, voltage rating by thickness or current flow path length, and current capability by area measured normal to the direction of current flow. Littelfuse Varistors are available with AC operating voltages from 2.5V to 6000V. Higher voltages are limited only by packaging ability.