[QuadList] Mains frequencies==(was Quad - progressive or interlaced?)

[Ted Langdell]

On Apr 10, 2010, at 3:23 AM, Trevor Brown wrote:

> I would like to say that 405/25  and 625/25 in the UK was forward  
> thinking
> Ie 24 FPS films could be played at 25FPS and nobody would notice,
> but it was because of the mains frequency and if you locked to it  
> picture hum would not move
> I don’t know why the mains was 50hz, I don’t think we planned it  
> that way in anticipation of television coming
> but you have to win one now and again.
>
> Trevor
> UK Member
>



The reason why we have incompatible AC power frequencies is this:
http://en.wikipedia.org/wiki/Utility_frequency

Though many theories exist, and quite a few entertaining urban  
legends, there is little certitude in the details of the history of 60  
Hz vs. 50 Hz.
The German company AEG (descended from a company founded by Edison in  
Germany) built the first German generating facility to run at 50 Hz,  
allegedly because 60 was not a preferred number. AEG's choice of 50 Hz  
is thought by some to relate to a more "metric-friendly" number than  
60. At the time, AEG had a virtual monopoly and their standard spread  
to the rest of Europe. After observing flicker of lamps operated by  
the 40 Hz power transmitted by the Lauffen-Frankfurt link in 1891, AEG  
raised their standard frequency to 50 Hz in 1891.[5]
Westinghouse Electric decided to standardize on a lower frequency to  
permit operation of both electric lighting and induction motors on the  
same generating system. Although 50 Hz was suitable for both, in 1890  
Westinghouse considered that existing arc-lighting equipment operated  
slightly better on 60 Hz, and so that frequency was chosen.[6]  
Frequencies much below 50 Hz gave noticeable flicker of arc or  
incandescent lighting. The operation of Tesla's induction motor  
required a lower frequency than the 133 Hz common for lighting systems  
in 1890. In 1893 General Electric Corporation, which was affiliated  
with AEG in Germany, built a generating project at Mill Creek,  
California using 50 Hz, but changed to 60 Hz a year later to maintain  
market share with the Westinghouse standard.




Ted Langdell
Secretary

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