Question: why us has 60 hz frequency supply?
Answer: THE HISTORICAL REASON BEHIND 60Hz SYATEM USED IN USA. The use of 50 versus 60 Hz is purely due to historical reasons, with companies in the US making 60 Hz equipment and those in Europe making 50Hz equipment so that they have a monopoly. ... Frequencies between 16⅔ Hz and 133⅓ Hz were used on different systems.