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kuppahalli
Active Contributor

Join Date: Mar 2011
Posts: 22

UPS Neutral

07/15/2011 5:28 AM

Why UPS output panels require Double Nutral.

Kindly explain

Regards

Murali
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cuba_pete
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Join Date: Dec 2010
Posts: 1895
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#1

Re: UPS nutral

07/15/2011 11:36 AM

Two is better than one (cheaper and easier to work with). Harmonic "control".
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pwr2thepeople
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Join Date: Aug 2007
Location: Indiana, USA
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#2

Re: UPS nutral

07/15/2011 6:28 PM

Non-linear loads cause harmonics in the power system. In 3-phase, 4-wire systems, the triplen harmonics (every 3rd odd multiple of the base frequency) are additive in the neutral connection. This causes excessive losses and heating of the neutral. By doubling the size of the neutral, the impedance (and therefore the losses and the heating) are reduced.

Emerson has a good explanation here.

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kvsridhar
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#3
In reply to #2

Re: UPS nutral

07/15/2011 11:21 PM

GA to you, and thanks for the excellent link.

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electricalexpert65
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Join Date: Oct 2009
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#4

Re: UPS Neutral

07/27/2011 9:46 AM

To carry the real "RMS" Neutral Current, which includes Triplen Harmonic Currents too, which accumulate in the Neutral, apart from the Fundamental Frequency Current. The true RMSNeutral Current can go as high as 200% of the phase current. And, any UPS is the main source of such triplen harmonic currents. Hence, the UPS Neutral is sized 200% (Double Neutral) so that it does not overheat even in the above situation.
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