DC is also great at: Corosion Explosions Arc welding Electrocution
I wonder if the cost savings take into account the price of all that thick copper needed to transmit DC throughout the datacenter. I've seen firsthand, 2 inch copper cables. There's a datacenter downtown that already has dc infrastructure in place, and a big battery, power stepping/switching, and UPS room. It might be more energy efficient, but I wouldn't bother with it, unless you could deliver +-12, =-5, and +3.3 to the rack. DC-to-DC conversion is notoriously inefficient. If you totally ruled that out, you might actually *see* some of the power savings. The other problem I'd see is with DC, the voltage (noticeably) decreases over distance. If that's noticeable in a datacenter, you'd have to have same-length runs to each rack. Might be especially nice if you didn't have to cool the large AC-to-DC substation as much as the datacenter, or if you could just put it on the roof. It will also probably be less safe, by the nature of DC not pulsing to release two shorted connections. DC circuit breakers are more expensive, and most folks are less experienced with DC.
On Dec 19, 2007 6:56 AM, Oren Beck [email protected] wrote:
On Dec 18, 2007 8:22 PM, David Nicol [email protected] wrote:
I've been suggesting this kind of thing for years
http://www.news.com/8301-11128_3-9835281-54.html?part=dtx&tag=nl.e433
-- Looking back, I realize that my path to software as a career began at the age of seven, when someone taught me to count in binary on my fingers. _______________________________________________ Kclug mailing list [email protected] http://kclug.org/mailman/listinfo/kclug
Actually, the standard telecom voltage has been 48 vdc, With two interesting triviata.
The term "Ring" refers to the ring of a plug that is the direct ancestor of what we use for musical instruments today
So "Tip" refers to the TIP of that same plug.
The other odd details of note are that in the original "Bell System" most phone wiring for POTS was on either Red Green Yellow 3w cable or Red Green Yellow Black 4c wire.
The oldest connections used Red and Green for the talk and dial circuit and the Yellow was often used for either Ringing or party line user identification -where the GREEN wire was POSITIVE and called TIP. The RED wire was Negative and called Ring The Yellow wire was called SLEEVE or the rearmost part of the plug with BLACK as a second sleeve in my recall of the systems. Curiously when I fact checked myself the Yellow wire use seemed to be regional and not totally consistent even in the same region..
Oren Beck
816.729.3645 _______________________________________________ Kclug mailing list [email protected] http://kclug.org/mailman/listinfo/kclug