What is a metal oxide varistor used for?
This type is commonly known as the metal-oxide varistor (MOV). Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages.
How do you test for metal oxide varistors?
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 metal oxide 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).
Are metal oxide varistors polarized?
No. Since MOVs provide bidirectional clamping, they are not a polarized device.
How do I check my varistor?
Turn the multimeter on and set it to read resistance times 1000 ohms. 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.
Do varistors degrade over time?
To address these transients, Metal Oxide Varistors (MOVs) are widely used in electronic circuits and power supplies. They absorb surges in the circuit input and maintain the voltage within acceptable limits. However, these surges and overvoltage transients can degrade MOVs over time.
What happens if a varistor fails?
Under different current conditions, failure modes include electrical puncture (see Figure 4), physical cracking (see Figure 5), and thermal runaway. Cracking happens because varistors are basically a ceramic material, and hitting them with a sharp high-amplitude surge is like hitting a dinner plate with a hammer.
