You can still find rotary frequency converters out there
They are big, loud, and not sort of thing you'd want in a non industrial space, but never the less....
From what one understands electronic especially modern offerings of frequency converters offer a more fine tuned output (pure sine waves, etc...). This makes them a good match for equally modern appliances/equipment that have sensitive electronics nowadays.
Believe it or not NYC subway system still used old rotary converters until rather recently (1999).
https://en.wikipedia.org/wiki/Rotary_converter#Obsolescence
https://en.wikipedia.org/wiki/Frequency_converter
They are big, loud, and not sort of thing you'd want in a non industrial space, but never the less....
From what one understands electronic especially modern offerings of frequency converters offer a more fine tuned output (pure sine waves, etc...). This makes them a good match for equally modern appliances/equipment that have sensitive electronics nowadays.
Believe it or not NYC subway system still used old rotary converters until rather recently (1999).
https://en.wikipedia.org/wiki/Rotary_converter#Obsolescence
https://en.wikipedia.org/wiki/Frequency_converter