When your voltage stages are unstable (ie: power stays on, but the actual voltage level may differ a lot from your 220V common), then I think that's the type of scenario where an AVR is helpful. Uninterruptible power supply (UPS) units are not only for info facilities and overly cautious https://mylessyaab.activosblog.com/32798760/the-greatest-guide-to-uninterruptible-power-supply-cyberpower