On Mon, 24 Dec 2007 11:57:28 -0500 snipped-for-privacy@aol.com wrote: | On Sat, 22 Dec 2007 11:12:11 -0800 (PST), " snipped-for-privacy@gmail.com" | wrote: | |>Need to figure the power factor for 208v power in our data center. I |>know that 208v power is more efficient than 120v but I want to figure |>the power factor in talking with customers. |>
|>So here's how we sell it. |>
|>- 20A / 120v power |>- 20A/ 208v power (assuming 2 phase) |>- 30A/ 208v power (assume 2 phase) |>- 60A/208v power - 3 phase. |>
|>Power power factor do I use to calculate the wattage any one circuit |>will run. |>
|>I'm using this formula: |>
|>A x V = WATTS |>
|>How do I calculate this with a power factor for 208v power? | | Your main issue is "what is the harmonic content on the neutral". If | this "data center" is really racks of single phase line to neutral | loads you should upsize the neutral at least 2 wire sizes to be on the | safe side.
But what if we run all the equipment directly on line-to-line power, at
208 volts in the typical case of three phase power in a large data center, or at 240 volts where they are supplied only with single phase? There will be no harmonics on the neutral in the 208/120 system because the neutral is not connected. And if each transformer supplying that system is D-Y (as opposed to Y-Y), there are again, no neutral currents upstream.
Now there will be harmonics on the phase lines. But it's less so because there are only 2 load groups contributing to triplens instead of 3 as in the case of the neutral in L-N loads.