Analysis on the damage of varistor

Varistor is a kind of voltage limiting protection device. Using the nonlinear characteristics of the varistor, when the overvoltage appears between the two poles of the varistor, the voltage clamp can be positioned to a relative fixed voltage value, thus the protection of the back stage circuit can be realized.

The failure mode of a varistor is mainly a short circuit, but a short circuit does not cause damage to a varistor, because the resistance is both positive and negative at the power supply inlet; the insurance is a good proof that it is not caused by a short circuit or overcurrent, but that the surge energy may be too large. Over absorbed power burns out the varistor; when the passing overcurrent is too large, it may also cause the valve to crack and open the circuit.