Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Data centers are transitioning from AC to DC

spectrum.ieee.org

Post reply on HN
Print view View original

181–190 of 432 posts

Re: Data centers are transitioning from AC to DC

#181

Post by throw0101c »

jacquesm wrote: post #53
KnuthIsGod wrote: post #49

Waiting for home DC. It is silly to have AC to DC converters in all of my wall connected electronics ( LED bulbs, home controller, computer equipment etc )

Not going to happen. For the same reason that the US never converted to a higher domestic voltage even though there are many practical advantages. The transition from one system to another at the consumer level would be terrible, even if there would be some advantage (and I'm not sure the one you list is even valid, you'd get DC-DC converters instead because your consumers typically use a lower voltage than the house…

> Not going to happen. For the same reason that the US never converted to a higher domestic voltage even though there are many practical advantages.

It would be relatively easy for the US to go to 240V: swap out single-pole breakers for double-pole, and change your NEMA 5 plugs for NEMA 6.

For a transition period you could easily have 240V and 120V plugs right next to each other (because of split phase you can 'splice in' 120V easily: just run cable like you would for a NEMA 14 plug: L1/L2/N/G).

What would be the real challenge would be going from 50 to 60Hz.

Re: Data centers are transitioning from AC to DC

#182

Post by crote »

mr_toad wrote: post #172
hristov wrote: post #9

It is absolutely stupid to talk about this as edisons revenge. If Tesla had the modern high power transistors needed to get high voltage dc out of the ac produced from a spinning turbine he would be all for high voltage dc too. Tesla understood that high voltage was needed for efficient long range transmission. He also understood that transformers were the inly remotely efficient way to climb up to and down from thes…

> If there was anything like a high power transistor back then he would have used that. Mercury arc rectifiers were used long before his death.

Yes, but a rectifier only rectifies. That's not going to give you DC-DC conversion - let alone converting it to a higher voltage for long-distance transmission.

Re: Data centers are transitioning from AC to DC

#183

Post by rkomorn »

throw0101c wrote: post #181
jacquesm wrote: post #53

Earlier quoted context omitted.

Not going to happen. For the same reason that the US never converted to a higher domestic voltage even though there are many practical advantages. The transition from one system to another at the consumer level would be terrible, even if there would be some advantage (and I'm not sure the one you list is even valid, you'd get DC-DC converters instead because your consumers typically use a lower voltage than the house…

> Not going to happen. For the same reason that the US never converted to a higher domestic voltage even though there are many practical advantages. It would be relatively easy for the US to go to 240V: swap out single-pole breakers for double-pole, and change your NEMA 5 plugs for NEMA 6. For a transition period you could easily have 240V and 120V plugs right next to each other (because of split phase you can 'splic…

> What would be the real challenge would be going from 50 to 60Hz.

Other way around, no? The US is already 60Hz.

Edit: I mostly remember this because the SNES games I used to buy in the US and brought back to Europe ran noticeably slower.

Re: Data centers are transitioning from AC to DC

#184

Post by jacquesm »

Tempest1981 wrote: post #156
jacquesm wrote: post #77

Earlier quoted context omitted.

The 'what is safer' question for DC and AC at the same effective current and power has a mixed set of answers depending on conditions. For instance, DC is more likely to cause your muscles to contact and not let go (bad), but AC is more likely to send your heart into ventricular fibrillation (sp?, also bad). AC arcs are easier to extinguish than DC arcs, but DC will creep much easier than AC and so on. From a persona…

> DC will creep much easier than AC Can you say more about "creep"? Is the resistance changing? Or is material actually migrating? Also curious why it's worse using DC.

https://www.eevblog.com/forum/beginners/understanding-high-v...

Re: Data centers are transitioning from AC to DC

#185

Post by jacquesm »

swamp_donkey wrote: post #158
jacquesm wrote: post #96

Earlier quoted context omitted.

I have a couple of those narrow escapes one of which led me to put a significant chunk of Eastern Amsterdam out of power. Another involved Beryllium oxide. 9 lives are barely enough.

Ah! Perhaps you are a member of the gigawatt club? Eligible for entry once you have accidentally tripped off 1000 MW of load or generation! No sweeping that under the table

I'm the idiot that sent a fairly high voltage spike into the grid setting off a cascade. Even years later I do not fully understand how it could happen, you'd think the grid would be low impedance enough to absorb a spike like that. But it set off a cascade on a part of the local grid that was known to be weak.

Re: Data centers are transitioning from AC to DC

#186

Post by jacquesm »

wincy wrote: post #157
jacquesm wrote: post #53

Earlier quoted context omitted.

Not going to happen. For the same reason that the US never converted to a higher domestic voltage even though there are many practical advantages. The transition from one system to another at the consumer level would be terrible, even if there would be some advantage (and I'm not sure the one you list is even valid, you'd get DC-DC converters instead because your consumers typically use a lower voltage than the house…

I just wish I could run my air conditioner and my desktop computer at the same time without flipping the breaker. The RTX 5090 is a space heater and will easily peg at the 600W it’s rated for, and so with that and an air conditioner window unit, I have to run a long cable from another unused room if I want to do anything that stresses the video card.

You can use nvidia-smi to reduce the powerdraw of the card to just below what will trip the breaker.

Re: Data centers are transitioning from AC to DC

#187

Post by ta9000 »

mikkupikku wrote: post #178
AndrewDucker wrote: post #170

Earlier quoted context omitted.

Why would we run out of Ga?

There's a component of modern culture that trains and expects people to be extremely pessimistic about long term human development. It results in situations above, where without any further information people just assume by default that were going to run out of a thing and are on some collision course with not just a disaster, but every single conceivable one. (Gallium is a byproduct of aluminum production. We aren't…

[flagged]

Re: Data centers are transitioning from AC to DC

#188

Post by crote »

HWR_14 wrote: post #154
mjuarez wrote: post #35

Earlier quoted context omitted.

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.

Can you explain why it's -48 VDC as opposed to 48 VDC with the + and - inputs mislabeled?

Because the chassis is connected to ground (as in, a literal grounding rod hammered into the soil) and by definition your 0V reference point.

The crucial difference is the direction in which the current is flowing: is it going "in to", or "out of" a hot wire? This becomes rather important when those wires are leaving the building and are buried underground for miles, where they will inevitably develop minor faults.

With +48V corrosion will attack all those individual telephone wires, which will rapidly become a huge maintenance nightmare as you have to chase the precise location of each, dig it up, and patch it.

With -48V corrosion will attack the grounding rod at your exchange. Still not ideal, but monitoring it isn't too bad and replacing a corroded grounding rod isn't that difficult. Telephone wires will still develop minor faults, but it'll just cause some additional load rather than inevitably corroding away.

Re: Data centers are transitioning from AC to DC

#189

Post by dist-epoch »

Animats wrote: post #118

800V to each rackmount unit, with hot plugging of rack units? That's scary. The usual setup at this voltage is that you throw a hulking big switch to cut the power, and that mechanically unlocks the cabinet. But that's not what these people have in mind. They want hot-plugging of individual rackmount units. GE has a paper about the power conversion design, but it doesn't mention the unit to rack electrical and mechan…

Or maybe you can require technicians to be in full-protection electrical suits.

Re: Data centers are transitioning from AC to DC

#190

Post by dist-epoch »

stego-tech wrote: post #8

I've been hearing this line for over a decade, now. "Immersion cooling will make data centers scale!" "Converting to DC at the perimeter increases density!" Yes, of course both of those things are true, and yes, some data centers do engage in those processes for their unique advantages. The issue is that aside from specialty kit designed for that use (like the AWS Outposts with their DC conversion), the rank-and-file…

These are GigaWatt data centers. For a single one they buy equipment by the container ship. Nothing is niche about it.
Post reply on HN