If the voltage stages are unstable (ie: power stays on, but the actual voltage amount may differ a good deal within the 220V regular), then I think that's the kind of circumstance where by an AVR is useful. For large power models, dynamic uninterruptible power supplies (DUPS) are sometimes made https://sergiovxyyx.fitnell.com/74580280/examine-this-report-on-uninterruptible-power-supply-ups