What Causes The Varistor To Break Down

What Causes The Varistor To Break Down

A varistor is a resistive component with nonlinear volt-ampere characteristics. It is mainly used for voltage clamping when the circuit is subjected to overvoltage, and absorbs excess current to protect sensitive devices.

The main parameters of varistors are: varistor voltage, flow capacity, junction capacitance, response time, etc. During use, what are the reasons for the damage of the varistor?

How a varistor works:

When the voltage applied to the varistor is lower than its threshold, the current flowing through it is extremely small, which is equivalent to a resistor with infinite resistance. That is, when the voltage applied to it is below its threshold, it acts as an off-state switch. When the voltage applied to the varistor exceeds its threshold, the current flowing through it surges, which is equivalent to a resistor with infinitesimal resistance. That is, when the voltage applied to it is higher than its threshold, it acts as a closed switch.

Causes of varistor breakdown: 

①The number of overvoltage protection exceeds the default number.

②Ambient operating temperature is too high.

③The varistor is squeezed so its shape is deformed.

④Whether it has passed the quality certification (inferior production material and process)

⑤The surge energy is too large, exceeding the absorbed power.

These reasons will cause damage to the varistor. When using it, you need to pay attention to its working temperature, the quality of the varistor, and so on. Correct use can reduce unnecessary troubles.

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