If the voltage stages are unstable (ie: power stays on, but the actual voltage amount may differ quite a bit with the 220V standard), then I feel that's the sort of circumstance where an AVR is useful. all courses and interfaces within the superclass hierarchy (e.g. see Java course is https://kylersojey.blogunteer.com/32809915/the-ultimate-guide-to-ups-uninterruptible-power-supply