A varistor, also known as a voltage-dependent resistor, is often an important electronic component in circuits, helping to prevent excessive voltage surges that could cause significant damage.
If you don’t know too much about them and how they work, it might be worthwhile to learn a little more before you buy one – it could make all the difference to your circuit to simply buy the right component rather than one that isn’t quite as suitable for the task at hand.
What does a varistor do?
Due to the fact that these can be used to protect circuits from voltage surges, it’s not hard to see why they can be a useful component. There’s also the fact that they can help to promote optimal operating conditions, which is another advantage that’s worth considering.
It’s important to note that, even if the voltage is lower than what the varistor was designed for, it can’t typically handle continuous surges.
While the project at hand might determine the specifications that you need from the component, you’re likely to find that these are generally important for any electronics where there’s a risk of excessive voltage.
Compared to other similar components, like TVS diodes, for example, varistors can be an excellent choice for several reasons, including being cost-effective, having higher clamping voltages, and overall being good for electronics that need a high capacitance.
Attributes of a varistor
Before you go ahead and buy a voltage-dependent resistor, it’s important to know the different things that go into making one and how this can have an impact on the effectiveness and longevity of the component. Here are some of the specifications that you should take into consideration:
• Capacitance – You’ll often find components in the range of 100-1000F
• Clamping voltage – The voltage across the terminals that cause it to close the circuit
• Leakage current – The current flowing while it’s in a non-conducting state
• Max. energy absorption – The limits that the varistor can dissipate for a pulse duration
• Response time – The duration where the circuit is exposed to the excess voltage before the varistor activates
• Surge current – The peak current of a waveform for pulse duration that can be applied without the varistor failing
When should you use a varistor?
As mentioned above, they can be great in many situations, but some applications are more common than others. In general, you’ll find varistors in power generating equipment, household electronics, telecommunication lines, and much more. For the most part, varistors are seen in most pieces of technology that we use on a daily basis.