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Data centers are transitioning from AC to DC

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Re: Data centers are transitioning from AC to DC

#81

Post by adiabatichottub »

torginus wrote: post #69
adiabatichottub wrote: post #48

Earlier quoted context omitted.

Really depends on what we're talking about. A lot of electrical safety equipment has a DC rating, usually something like 90VDC/300VAC. Also, most DC equipment just isn't going to have the stored energy to generate a big arc. Well, except batteries, and we're already piling them all around us.

I mean it depends, but for dual rated stuff has both a voltage and current limit, both of which are way lower. Like typically a 230V/20A AC switch can switch 24VDC/2A. And the energy is not in the equipment, its in the mains (or batteries like you said, or PV panels)

Right, but that's why I mentioned safety equipment. Your common DIN-mount UL-489 branch circuit breaker will be rated for the same trip current, same short circuit current rating (SCCR), but lower voltage. So you can use the same wiring and breakers as you might have with AC and your 48V battery bank won't vaporize the $5 hardware store toggle switch that somehow became a shunt.

Re: Data centers are transitioning from AC to DC

#84

Post by pocksuppet »

MathMonkeyMan wrote: post #42
bluGill wrote: post #16

Earlier quoted context omitted.

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.

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 dra…

The phone grid predated the electrical grid. There was no other choice for power.

Actually, there was one. Even earlier phones had their own power. A dry-cell battery in each phone, and every 6 months, the phone company would come around with a cart and replace everyone's battery. Central battery was found to be more convenient, since phone company employees didn't have to go around to everyone's site. Central offices could economize scale and have actual generators feeding rechargeable batteries.

Re: Data centers are transitioning from AC to DC

#85

Post by bigiain »

jacquesm wrote: post #78
bigiain wrote: post #75

Earlier quoted context omitted.

If you could get that 100,000Amps flowing through your speaker wire, the vaporised copper and the plasma channel would probably keep your 100MW flowing, at least until your building caught fire.

Even your monster cable? ;)

Well, it'd still vaporise, but it'd sound smoother and more musical as it did it, and the soundstage from the plasma arc would be _stunning!_

Re: Data centers are transitioning from AC to DC

#86

Post by pocksuppet »

scheme271 wrote: post #73
ericd wrote: post #45

Earlier quoted context omitted.

heh man, I'm glad you got out of that easy, I definitely wore safety glasses 100% of the time after my experience. I think a lifetime of experience with dangerous wall outlets and harmless little 1.5V/9V DC cells teaches us the wrong lessons about DC safety. I've since heard stories of wrenches exploding when they fall across EV high voltage battery terminals. Wrenches aren't supposed to be explosive. The electrician…

A bunch of those big breakers require two people. One person in a flash suit and another with a 2m long pole around the first person. That way if an arc flash happens, the second person can yank the first person to safety without also getting hurt.

Why don't they use the pole to flip the breaker from 2m away?

Re: Data centers are transitioning from AC to DC

#87

Post by jazzyjackson »

scarecrowbob wrote: post #76
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 )

Well, having spent some time operating a 12VDC system last year when I moved into some shacks, I will say that I find it a lot more convenient to run 120VAC. I end up converting stuff anyhow, because all my loads run at different voltages- even though I had my lights, vent fan, and heater fans running on 12V I still ended up having to change voltages for most of the loads I wanted to run, or generate a AC to to charg…

Catch me wiring my house with 20V USBC ;)

Re: Data centers are transitioning from AC to DC

#88

Post by catlikesshrimp »

Mistletoe wrote: post #58
adrr wrote: post #23

Our houses should be DC. So wasteful to have all these bricks to change to AC to DC.

Modern bricks really aren’t that inefficient though. An Apple charger is like 90% efficient. A DC to DC converter is about that efficient or worse.

The power adapters became so efficient that we have to transition to wireless charging to keep it down

The irony...

Re: Data centers are transitioning from AC to DC

#90

Post by tverbeure »

bluGill wrote: post #16
otterley wrote: post #7

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...

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.

-48V! :-)
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