When your voltage concentrations are unstable (ie: power stays on, but the particular voltage level may differ quite a bit through the 220V regular), then I feel that's the sort of circumstance the place an AVR is useful. For giant power units, dynamic uninterruptible power provides (DUPS) are sometimes applied. https://marcoprqon.fireblogz.com/65070397/an-unbiased-view-of-uninterruptible-power-supply-apc