[GreenKeys] History - Why voltages and frequencies are chosen (5v & 3.3v logic, 6.3v filaments, 120/220 VAC, 50/60Hz etc)

[tony j. podrasky]

That's what we learned in engineering school.

The New York City subway system was running on something like 30Hz back
in the 50's - and you could see the lights flicker.

As a little kid I found it interesting and a little scary at the same time.

UE,
W6ESE - tony
NNNN
ZCZC

Keith Lueck wrote:
> I think 60 Hz was chosen b/c it's above the human perception for flicker 
> - although you'd think that the thermal time constants of incandescent 
> filaments (the only light source at the time) would've tended to smooth 
> that out anyway.  Certainly a low frequency was chosen to minimize the 
> rotational speed of large generating equipment.  IIRC, there used to be 
> some industrial systems that used 25 Hz, here in the US.   Don't know 
> why we ended up w/ 60 Hz and the Brits used 50... 
> 
> Early (mechanical) RF alternators had a nasty habit of flying apart - 
> literally sending shrapnel everywhere b/c of their high rotational 
> speeds and large numbers of poles....  but that's another story.  
> 
> JM2CW,
> 
> Keith
> 

-- 
Tony J. Podrasky | Weed's Axiom:
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