Nominal parameter of varistor

Varistors are represented by the letter "MY", if “J”is added to the household one, The letters W, G, P, L, H, Z, B, C, N, K are used for voltage stabilization, overvoltage protection, high frequency circuit, lightning protection, arc extinguishing, noise elimination, compensation, demagnetization, high energy or high reliability respectively. Although varistors can absorb large surge energy, they cannot withstand sustained currents above milliamperes, which must be taken into account when being used as overvoltage protection. In the selection of varistor, two parameters, nominal voltage-sensitive voltage V1mA and current-current capacity, are generally selected.

The so-called voltage-sensitive voltage, that is, breakdown voltage or threshold voltage. It refers to the voltage value under the specified current, which is measured when the 1mA DC current is passed into the varistor in most cases. The voltage range of the product can range from 10 to 9, 000 V. It can be selected correctly according to specific needs. Generally, V1mA1. 5VpU 2.2VAC, in which V p is the peak value of the rated voltage of the circuit. VAC is the effective value of rated AC voltage. The choice of voltage value of ZnO varistor is very important, which is related to the protection effect and service life. If the rated power supply voltage of an electrical appliance is 220 V, the voltage value of the varistor

V1mA=1.5Vp=1.5×1.414×220V=476V，V1mA=2.2VAC=2.2×220V=484V，Therefore, the breakdown voltage of the varistor is between 470-480V.