Hello Mechanical,
here's my 2 cents...
the output frequency of an AC generator / alternator depends on the RPM... most common number of poles are 2, 4 , and 6 pole... the drive speed for 60/ 50 hz is 3600/3000 RPM for a 2 pole, 1800 / 1500 RPM for a 4 pole, 1200 / 1000 RPM for 6 pole..
sounds...