On Tue, 28 Feb 2012, Edward Ned Harvey wrote:
From: [email protected] [mailto:[email protected]]
On Behalf Of Doug Hughes
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
Which is more expensive?
You run AC to your UPS, convert it to DC, convert it back to AC, deliver it
to your systems, and convert it to DC again...
Or
You run AC to your big UPS, and deliver 48V DC to all your systems using 4A
wire.
I've been thinking about this issue for home use, especially with Solar
power.
currently you take the DC input (solar), run it through an inverter to
feed it to a UPS, to convert it to DC (to charge the batteries), to
convert back to AC to run to the power supply in the PC to convert back to
various DC levels to use inside the machine.
While AC->DC converters are ~90% efficient, DC -> AC inverters are less
so, topping out around 70-80% efficiency.
It seems like it should be possible to do a lot better.
David Lang
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