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Varistors are voltage-dependent resistors that act as internal surge protectors in electrical circuits. They resist electricity based on the energy flowing through them, channeling and diverting currents to specific locations. They are found in almost all modern electrical appliances and are most important in generators and transformers. Varistors are made of metal composites that absorb and conduct electricity at certain levels. They are not safety devices, but they can prevent serious problems by setting limits at acceptable energy levels. Different uses have different capacity requirements and specifications.
A varistor, also sometimes called a “voltage-dependent resistor,” is a part of the electrical circuit that helps channel and shunt volts to keep the energy levels flowing through it constant. Understanding the specifics of what it does and how it works can be tricky. However, on a very general level, these components function as internal surge protectors and help keep electrical currents contained within a given device. They are usually made of metal composites that have been specially formulated to absorb and conduct electricity at certain levels, even though they are not normally considered to be true conductors. Almost all modern electrical appliances contain them and they are perhaps most obvious and most important in things like generators and transformers which receive regular surges of high voltage currents.
What does he do
The word “varistor” is a portmanteau of the words “variable” and “resistance,” and in layman’s terms, that’s exactly what this component does: it resists electricity based on how much energy is flowing through it and how strong that energy is. Its main role is to act more or less like a spark gap that protects circuits from runaway voltage. Without them, electric currents could flow freely through a high-level system. This could be dangerous to humans and also runs the risk of frying or damaging the circuit itself.
These components are often very small, although their dimensions are usually relative to the type of device or appliance in question. In smaller devices such as personal computers or home electronics they usually do not exceed about 0.4 cm in diameter, but in generators and transformers they can be much larger. Most are circular and generally have two pins or prongs extending from them and into the circuit of whatever they’re working to protect. Many of the smaller examples are circular in shape and often said to resemble small coins or tiny batteries, although square-shaped models are also common. There’s a lot of variation when it comes to looks, and a lot of that has to do with the specifics of the use. Small appliances necessarily have different needs than bigger, more powerful things like telecom hubs and computer servers.
Most common uses
Most devices that use electricity need voltage suppression, which means that almost every electronic device, from alarm clocks to industrial machinery, needs a variable resistor. In small appliances this component is often not very noticeable and often works in conjunction with other voltage control measures to provide basic surge protection. Surge protectors — long strips of outlets that plug into wall outlets — are some of the most common places to find these resistors in your home. However, the bigger machines are the ones that tend to depend on them more openly.
Things like transformers, telephone switchboards, and large mechanical appliances often depend on powerful resistors to prevent total meltdown and dangerous working conditions. Varistors in these settings tend to be a bit more powerful and often have the ability to trigger the entire device to shut down if too high voltages are detected. This usually requires immediate repairs and eventual replacement of the tracking device, but in most cases can save the device as a whole.
How does it work?
Generally speaking, these components work by diverting currents through an array of ion-charged particles sandwiched between two opposing metal plates to create barriers and junctions, effectively channeling currents to specific locations. The most common type is known as a metal oxide varistor or MOV. Examples in this category use grains of zinc oxide to absorb and more or less trap moving currents and force those currents to flow in only one direction. When currents fold back on themselves, the risk of problems increases.
Grains usually carry an electric charge in and of themselves, which helps when it comes to absorbing and directing currents. In most cases it also leads to greater adaptability. Small currents with low to moderate voltages pass through the plates and usually don’t require much action. However, high voltage currents can overwhelm normal diode junctions, which causes resistors to kick into action. As a result, the MOV can be said to have high resistance at low voltages but low resistance at high voltages. In other words, it’s flexible in a variety of settings.
Importance of energy containment
The primary role of this type of device is to channel and divert energy, but it is not a safety device. Too powerful bursts of energy can damage or even destroy it. Lightning, for example, often destroys these types of resistors or causes them to melt.
However, most problems can be predicted and in most cases resistors are able to prevent serious problems. Two of the most important parameters are the response time, i.e. how long it takes for the device to fail, and the defined maximum current and breakdown voltage, which set limits at acceptable energy levels. Different uses have different capacity requirements and specifications.
