Want to move to all 208V for server racks

Alex Rubenstein alex at corp.nac.net
Fri Dec 3 12:23:49 CST 2010


> 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.
> 
> With the cheaper switching power supplies, one will often see significant 3rd
> harmonics in the waveforms(*).  The 3rd harmonic, across a 3 phase circuit,
> are additive on the neutral.  In worst case, your (common) neutral current
> 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 currents." I meant that to mean, as well, less harmonics.






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