Metal oxide varistors and multi layered varistors.
Metal oxide varistor circuit.
A metal oxide varistor or mov is the blue or orange colored circular component that you can commonly spot on the ac input side of any power supply circuit the metal oxide varistor can be considered as another type of variable resistor that can vary its resistance based on the applied voltage across it.
A metal oxide varistor is frequently used in different circuits along with a fuse.
The metal oxide varistor is designed to protect various types of electronic devices and semiconductor elements from switching and induced lightning surges.
This type contains a ceramic mass of zinc oxide grains in a matrix of other metal oxides such as small amounts of bismuth cobalt manganese oxides sandwiched between two metal plates which constitute the electrodes of the device.
The radial leaded disc type is the most common version.
The metal oxide varistor or mov is.
When a high current passes through a mov its resistance value decreases and acts as a short.
The metal oxide varistor or mov is a voltage dependent nonlinear device that provides excellent transient voltage suppression.
The circuit we will build is shown below.
This mov circuit will clamp up to 300vac if a power surge allowing transients into the circuit were to be that high.
They are available in many values for specific voltage ranges.
First let us consider the component to have an open circuit as shown in figure 1 a.
Metal oxide varistors movs are available in a variety of form factors and sizes for a broad range of applications.
The circuit of the mov is shown below.
These two are connected in parallel to the protected circuit.
The main components used to protect the circuit are fuse and varistor.
300vac metal oxide varistor.
The most common modern type of varistor is the metal oxide varistor mov.
Metal oxide varistor circuit.
An mov s voltage rating called the varistor voltage is the voltage across a varistor when a current of 1ma is passed through the device.
Metal oxide varistors or mov s are typically made from a small disk shaped metal zinc oxide material.
The energy of the incoming surge is partially conducted and partially absorbed protecting the circuit.
They are composed primarily of z n o with small additions of other metal oxides such as bismuth cobalt magnese and others.
Working of metal oxide varistor mov working of metal oxide varistor mov the working of a mov is shown in the figure above.
The component starts conducting as soon as the voltage across it reaches the threshold voltage.
Varistors are voltage dependent nonlinear devices which have electrical characteristics similar to back to back zener diodes.
The components needed to build this circuit are shown below.
When the circuit is exposed to a high voltage transient the varistor starts to conduct and clamps the transient voltage to a safe level.
