Matching Surge Protective Devices to Their Environment

A method is described for the rational selection of metal oxide varistors as surge protective devices in low-voltage applications, combining data on the surge environment and device characteristics. Fuses that may be connected in series with the varistors will be exposed to current surges resulting from the varistor operation. Experimental results on the effect of repetitive current surges on such fuses are described, and some guidance is provided on the necessary derating of fuses for series applications with varistors.