Surge protection of low-voltage AC power by MOV-based SPDs

Protection against surges and transient voltages is an essential part of almost any properly designed electrical and electronic equipment today. And the Metal Oxide Varistor (MOV) is the single most important component in the overwhelming majority of the surge protection devices (SPD) designated to provide such protection. The level of protection provided by the SPD and its duration in service depend very much on the properties of the MOV. We discuss the ways of improvement of three major characteristics of the MOV-based SPDs. These properties are: the clamping (residual) voltage, the ability to withstand a temporary overvoltage, and the longevity. The improvement of these characteristics can be achieved by the selection of the right type of MOVs, by the special MOV packaging technology, and by making the length of wires connecting a SPD to the circuit as short as possible.