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

[Pete Lancashire]

Here's a paper on US line frequency

http://www.ece.umn.edu/class/ee4721/NOTES/Why%2060%20Hz.pdf


On Wed, Nov 21, 2012 at 12:57 PM, Keith Lueck <kwlueck at swbell.net> 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
>
>
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