----- Original Message -----
From: Chris Wells
To: Tania Grant
Sent: Saturday, August 18, 2001 10:54 PM
Subject: Re: CE test suite for computers
Jumping into the middle of this.......
In Europe there are a lot of older buildings with half sized neutrals relative
to the supply phases.
In the USA we tend to have newer designs and tend to have at least neutral
circuits = to the phase circuits.
In newer buildings we are pushing for 200% neutrals.
This is all due to the effect of single phase loads and the tripplen harmonics
they create.
The 3, 9 etc do not cancel on the neutral- they tripple up on the neutral
causing large harmonic loads.
This can cause voltage drops on the phases and over heating of the neutrals -
even fires.
I assume this is why Europe is pushing for PFC front ends on Power supplies
above 50 or is it 75W?
The PFC front end does correct Power Factor, but more importantly it pulls
current closer to a 50 or 60 Hz sinusoide.
It eliminates much of the lower harmonics with distortion only showing up at
the higher harmonics like the 27th or higher.
At that point the THD levels are very low and insignificant.
Is this related to the Energy STar Program - I have no idea.
Hope this makes some sense relative to the disscussion :-)
Regards
Chris Wells
Senior Design Engineer
Cutler-hammer
well...@eaton.com
----- Original Message -----
From: Tania Grant
To: John Woodgate ; emc-p...@majordomo.ieee.org
Sent: Saturday, August 18, 2001 12:32 PM
Subject: Re: CE test suite for computers
Dear Mr. Woodgate,
Most people will never understand anything unless it is explained to them.
Merely stating
that the power distribution in Europe and America is not the same, is not an
explanation but could even be construed as a lofty put-down.
If anyone out there can explain the difference between American and European
power distribution, and why harmonics are not such a big problem in the U.S., I
am sure that many of us will be extremely grateful.
And can someone explain to me why the European Community is adopting the
American Energy Star Program? -- Albeit rendered in their own language!
taniagr...@msn.com
----- Original Message -----
From: John Woodgate
Sent: Friday, August 17, 2001 3:37 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: CE test suite for computers
I read in !emc-pstc that Pettit, Ghery <ghery.pet...@intel.com> wrote
(in <d5e932f578ebd111ac3f00a0c96b1e6f09506...@orsmsx31.jf.intel.com>)
about 'CE test suite for computers', on Fri, 17 Aug 2001:
> Also EN 61000-3-3 needs to be considered. Useless standards, if you
ask me.
>
That's because you, like most Americans, do not understand the problems
in Europe. Because the power distribution networks in Europe and the
Americas are very differently configured, you have far fewer problems
with harmonics and voltage changes, and voltage changes seem to be much
more tolerated, in USA anyway.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Eat mink and be dreary!
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