MOV Block and metal oxide varistor application

In general, the primary case of varistor breakdown is localized heating caused as an effect of thermal runaway. metal oxide varistor application is to a lack of conformity in individual grain-boundary junctions, which leads to the failure of dominant current paths under thermal stress. If the energy in a transient pulse (normally measured in joules)MOV Block is too high, the device may melt, burn, vaporize, or otherwise be damaged or destroyed. This (catastrophic) failure occurs when "Absolute Maximum Ratings" in manufacturer's data-sheet are significantly exceeded.