[133041] in North American Network Operators' Group
RE: Want to move to all 208V for server racks
daemon@ATHENA.MIT.EDU (Alex Rubenstein)
Fri Dec 3 13:27:58 2010
From: Alex Rubenstein <alex@corp.nac.net>
To: Gary Buhrmaster <gary.buhrmaster@gmail.com>, Jay Nakamura
<zeusdadog@gmail.com>
Date: Fri, 3 Dec 2010 13:23:49 -0500
In-Reply-To: <AANLkTinfMFZ+iNTvQ4zmYg0DukSBkNDTmotrWkrGxh92@mail.gmail.com>
Cc: NANOG <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> btw, one thing I do not recall seeing on this thread is that 208v avoids =
one of
> the common problems with 120v, which is the third harmonic issue.
>=20
> With the cheaper switching power supplies, one will often see significant=
3rd
> harmonics in the waveforms(*). The 3rd harmonic, across a 3 phase circui=
t,
> are additive on the neutral. In worst case, your (common) neutral curren=
t
> may exceed the line currents. Proper engineering for significant 120v
> distribution in new DC construction often requires double sized neutrals =
to
> mitigate against this.
> Using 208v mitigates this particular issue.
I should have been clearer, when I originally said, "it lessens neutral cur=
rents." I meant that to mean, as well, less harmonics.
