jnord3d ago

In Edison’s Revenge, Data Centers Are Transitioning From AC to DC

https://spectrum.ieee.org/data-center-dc

Data Center DC Embraces 800V Power Shift

Could switching to 800 V DC be the key to more efficient data centers?

IEEE Spectrum
Show threadotterley

DC power has been an option for datacenter equipment since I was a young lad racking and stacking hardware. Cisco, Dell, HPE, IBM, and countless others all had DC supply options. Same with PDUs. What’s old is new again.

See e.g. https://www.dell.com/support/kbdoc/en-us/000221234/wiring-in...

PowerEdge: Wiring instructions for a DC power supply unit | Dell US

This article provides some checklist to prevent unnecessary components replacement on DC power supply implementation.

Mar 25 at 1:34amWeb
Show threadbluGill3d ago
48vdc was common in phone exchanges. They filled the basement with lead-acid batteries and to could run without the grid for a couple weeks. In turn the phone was 99.999% reliable for decades.
Show threadmjuarez3d ago

Not to be _that_ guy, but it was technically -48V DC.

Honestly, that was pretty surprising to me when I had to work with some telco equipment a couple of decades ago. To this day, I don't think I've encountered anything else that requires negative voltage relative to ground.

Show threadyostrovs3d ago
Check out older English cars.
Show threadbluGill3d ago
positive ground used to be in all cars. When they went from 6 volts to 12 the disadvantages became appearant fast and so everyone went negative ground then (mid 1950s). I am not clear why positive ground was bad (maybe corrosion?)
Show threadservo_sausage3d ago
Is that something other than a labelling convention? Is ground actually connected to a earth stake?
Show threadCamperBob23d ago
Cathodic protection against corrosion was the goal of using -48V, in the telcos' case.
Show threadjacquesm3d ago
Yes, and that tiny little difference can cost you a lot of expensive gear if you run it off the battery and plug in a serial port or something like that. You'll also learn first hand what arc welding looks like without welding glass.
Show threaddivbzero3d ago
Interesting, so this is why the phone line still worked when power was out across the whole town.
Show threadMathMonkeyMan3d ago

Yeah I always heard that the phone lines carried their own power, and in Florida the phones did keep working when the power went out, but I never knew why.

So the grid was always charging up the lead acid batteries, and the phone lines were always draining them? Or was there some kind of power switching going on where when the grid was available the batteries would just get "topped off" occasionally and were only drained when the power went out?

Show threadbluGill3d ago
Grid charging batteries, phone draining them as I understand. Of course there were switches all over the us so I can't make blanket claims but from what I hear that was normal.
Show threadidiotsecant3d ago
I still have a bunch of 48vdc comms gear in my powerplant.
Show threadAbanoubRodolf3d ago
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