Brownouts (fnarr fnarr)
I used to work somewhere that had one of the first HP/PA HPUX systems (I think, mid 1990s) outside the USA. They were very pleased with their automatic voltage sensing auto-switching PSU that just worked with 110V or 240V or whatever, supposedly. We were in Barrington Hall, in a village. At least the place had 3-phase supply.
We had brownouts.... we also had power cuts and the supply was delicate enough that procedure was to turn off everything we could when it went dark; sysadmins would then come round and turn it on one by one so that the startup load of all the discs didn't happen all at once and trip it out again.
But in some shapes of brownout, the HP/PA machine's clever PSU auto-switched to 110V. Great. But it was very slow at switching back to 240V when the mains came back up, and failed with smoke. Every time the project was delayed a week whilst they shipped another PSU; after some months they sent a better PSU without the stupid in it, and all was well.