Want to move to all 208V for server racks
Lamar Owen
lowen at pari.edu
Sat Dec 4 16:05:56 UTC 2010
On Friday, December 03, 2010 02:54:37 am Chuck Anderson wrote:
> Here's a question for you. How do you calculate the total current &
> power capacity of a L21-20 or L21-30, and how do you do the
> calculations in order to balance the load between the phase legs?
> This seems like it would be a trivial thing to do, but given that the
> three legs are 120 degrees out of phase with each other, I don't think
> you can just do normal addition.
You would be correct. A pretty good three-phase calculation reference can be found at http://www.3phasepower.org/3phasepowercalculation.htm
It is vector addition, and with the angles involved you end up multiplying and dividing by the square root of 3 a lot.
Also see the wikipedia article, and here's a few others:
http://www.gavinelectrical.com/content/threephase.htm
http://www.servertech.com/uploads/documents/0000/0236/3-Phase_Power_in_the_Data_Center.pdf
That last PDF is directly related to this discussion, and a good read.
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