On 2/27/2012 8:18 PM, Darrell Fuhriman wrote:
utilizing less storage elements, and producing less waste. That is true.
Or you can just design a smarter A2D power supply, which efficiently uses
the 120V single phase power.
I continue to wonder why more data centers don't use -48V DC distribution.
Because it would hugely expensive in terms of copper. to deliver 200W at
-48V DC requires copper capable of carrying 4A. To do so at 208V
requires a cable capable of 1A. There are some ways around this by
distributing at what is called high voltage DC out to the floor which
gets a slight advantage because at the same AWG, DC has a 5% efficiency
advantage vs AC. But then you have to have some significant power
infrastructure distributed at every row (almost 1 of every 3 racks) to
convert from HVDC to low voltage DC. There are not very many vendors to
do this, it's relatively new, and so the costs are a bit higher. It does
have some further advantages at the UPS because you don't have to worry
about phase matching and you can save efficiency in AC to DC and DC back
to AC conversions. The failover is simplified to some specialized
diodes, which is cool. The capital costs typically end up making the
decision a wash at the current time.
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