Re: how does voltage from a wall plug vary with time
From: aasiyah (alam_seher_at_hotmail-dot-com.no-spam.invalid)
Date: 02/13/05
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Date: 13 Feb 2005 03:35:07 -0600
> Nick Rousewrote:
Uncle Al <UncleAl0@hate.spam.net> wrote in message
news:<420A4E25.357F5B08@hate.spam.net>...
>
> Although 50Hz lighting may flicker in absolute terms more than 60Hz
> the
> difference is not nearly as much as is perceived by those who have
> lived
> most of their lives in 60Hz areas when visiting 50Hz areas.
> Experiments have
> shown that long exposure to one frequency of flicker causes a
> distinct
> notch in the visual frequency response. In visiting America from
here
> in Britain, I find the lighting somewhat more flickery that at home
> but not as much as American friends visiting here who find it hard
> to see how I put up with such lighting.
> Transformers built for 50Hz are not less efficient than those built
> for 60Hz.
> but plug in a transformer built for 60Hz into a 50Hz supply and it
> will heat
> up more. If built to operate at the same maximum magnetic flux
levels
> (by having proportionately greater core cross section or
> proportionally more primary
> turns or a bit of both) a 50Hz transformer would be more efficient
> than
> a 60Hz one although bigger.
> Even higher frequencies give much smaller devices but not
necessarily
> much cheaper as
> steps have to be taken to keep the losses down. 400Hz aircraft
> transformers tend to use very thin laminations of cobalt iron which
is
> many times more expensive than silicon steel used at 50 & 60 Hz
>
> The cleanliness of the sinewaves is very dependant on the nature of
> the
> load in your vicinity. A largely linear load will leave the
waveform
> clean
> but substantial non-linear loads such as discharge lighting,
> rectifiers or
> non-power factor corrected switched mode power supplies can distort
> the
> voltage waveform for other users substantially. 5% harmonic
> distortion is quite
> common close to sights where such loads make up a large fraction of
> the
> power used locally.
>
> The original question asked about wall plugs (sockets) in Europe.
> Anti-phase
> live conductors are never found in domestic supplies (although
> building
> sites use portable transformers that transform 240 or 230V down to
an
> earthed
> centre tapped 110V). As stated in an earlier post three phase
supplies
> are very rare here in domestic situations and in the few cases they
> are used
> they tend to be fixed wiring. I have not come across any three phase
> sockets approved for use in Europe that you would want in your
house.
>
> Nick Rouse
Why isnt three phase used, what is the 'danger'?
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