MOV (Metal Oxide Varistors) are critical components required in most power supplies when compliance with surge requirements is a must. The surge withstand voltage will depend on the size of the bulk capacitors (if any present), series components (like inductors for EMI filters) and also to a certain degree on how the layout is made.

The rated current refers to the maximum current that can repetitively go through the Varistor without major degradation of the component itself. Care should be taken that the varistor has a current rating above the maximum current flowing through it during a surge event.