The nameplates say 230 / 50 Hz, that is what they are specified for. Typically +/- 6%, maybe 10% of voltage, and maybe +/-3Hz of frequency. Maybe additionally a maximum height above sea level is given.
If you run a device out of the range of the specs you'll loose the warranty. That is a law (almost?) everywhere.
So your main issue is just ridiculous to me and not worth any further discussion.
There are some devices that will usually run out of specs without problems but on your own risk. Those obviuosly don't. Some ideas for the 'why?' have been already mentioned.
Another question is maybe if it is possible to prevent future damage for the still running ACs by changes to the hardware. Is this still of importance?
Wolfgang
