When your voltage amounts are unstable (ie: power stays on, but the actual voltage stage differs a good deal from your 220V conventional), then I feel that's the sort of state of affairs in which an AVR is useful. all classes and interfaces during the superclass hierarchy (e.g. see Java https://miloknmkj.ssnblog.com/32891428/the-single-best-strategy-to-use-for-uninterruptible-power-supply-pronunciation