If the voltage ranges are unstable (ie: power stays on, but the particular voltage degree may differ lots from the 220V normal), then I believe that's the kind of situation exactly where an AVR is useful. This reply incorporates a number of the most valuable measurements of this issue on https://tattoo07406.blogsvirals.com/32943764/helping-the-others-realize-the-advantages-of-uninterruptible-power-supply-cyberpower