[Milsurplus] 60 Hz.

[Richard Brunner]

 Can anyone say why 60Hz was chosen?

Several reasons:
Machinery construction (motors, transformers) is most economical and 
efficient at 50-60 cycles.  As the frequency goes up equipment gets smaller 
requiring less iron and copper, but much over 60 cycles the iron losses 
start increasing unreasonably.

For power transmission the cable reactance becomes significant at higher 
frequencies.

50-60 cycles was considered a reasonable compromise for incandescent light 
flicker.  I have seen lights on a 25 cycle system, and light flicker is very 
noticable.

Low frequency (16 2/3, 25 cycles) is advantageous for traction motors, but 
when it is rectified to use dc, or a cycloconverter (changing higher 
frequency to lower frequency) is used, there is no advantage in low 
frequency power.  Indeed, new systems use 50-60 cycle power distribution for 
traction.

Richard Brunner, AA1P