Why is the varistor called overvoltage protection device?

The varistor is not a sensory pressure. It is a voltage susceptor. It is a bit like a fuse. It will break down beyond its own voltage and be protected by an open circuit. The varistor is a voltage-limiting protection element that absorbs or releases the lightning induced overvoltage and the operating overvoltage present in the line. At the same time, as a component of the line system and equipment, it must also withstand the temporary over-voltage of the low-voltage power supply line and equipment. Voltage.

Therefore, the varistor must withstand the effects of lightning overvoltage, operating overvoltage and temporary power frequency overvoltage when applied in the line. The varistor voltage is usually expressed by the voltage at 1 mA DC current across the varistor. Pass the flag voltage. This voltage is called varistor voltage and is also commonly used to indicate that the error range of the varistor voltage is generally plus or minus ten percent.

In test and practical use, the varistor voltage is usually reduced by 10% from the normal value as a criterion for varistor failure. In addition, its large impulse width of inrush current is much smaller than the actual pulse current width of high-power semiconductor systems, so short-circuit conditions often occur. Varistors are often used as overvoltage protection devices, but their current capacity is large, but the capacity is not large.

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