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

[Pete Lancashire]

even more .

http://en.wikipedia.org/wiki/Utility_frequency#History

On Wed, Nov 21, 2012 at 1:28 PM, Pete Lancashire <pete at petelancashire.com>wrote:

> 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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