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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

#91

Post by [deleted] »

arijun wrote: post #14
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…

Also, if anything would have been Edison's revenge it would have been HVDC, where they're sending power long distances with DC. (But as you said, even there it wouldn't make a ton of sense, since they were arguing in a different era).

[deleted]

Re: Data centers are transitioning from AC to DC

#92

Post by jazzyjackson »

analog31 wrote: post #34
kccqzy wrote: post #29

Earlier quoted context omitted.

That’s actually a recent phenomenon. Before the age of electronics most household appliances either worked with AC or DC equally well (like incandescent bulbs) or worked well with AC only given the technology at the time (think anything with a motor, fans, HVAC compressors etc).

Taking it to an extreme, the house I lived in while in grad school had wall lamp fixtures that doubled as electric and gas lamps. At some point I imagine it would have been possible to choose between using electric or gas by either flipping the switch or turning a valve. They said "Edison Patent" on them. We could have lit the house on AC, DC, or gas. Thinking about the failure modes gave me the heebie jeebies, but t…

It’s kind of fun that light switches predate electricity. I think you used to turn a key, I guess you were turning a valve? Now that I think of it using a key to operate a valve makes a lot of sense but you don’t see it too often, well, I guess you want to turn things off without needing to find a key…

Re: Data centers are transitioning from AC to DC

#93

Post by manwe150 »

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…

I suppose that still begs the question somewhat, since the US does have 240V (2 phase) already driving many appliances. Why hasn’t it ever become standard for luxury kitchens to have a European-style outlet for use with a European kettle? I know the US already has a different 240V plug shape, so it might have to be an unlicensed installation, but surely someone wanted hot tea faster and did that calculus before?

Re: Data centers are transitioning from AC to DC

#94

Post by jacquesm »

bigiain wrote: post #85
jacquesm wrote: post #78

Earlier quoted context omitted.

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!_

It's almost worth the experiment and your cables are a sacrifice I'm willing to make. For science, of course.

Re: Data centers are transitioning from AC to DC

#95

Post by themafia »

arijun wrote: post #14
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…

Also, if anything would have been Edison's revenge it would have been HVDC, where they're sending power long distances with DC. (But as you said, even there it wouldn't make a ton of sense, since they were arguing in a different era).

The two primary reasons to do that are to allow the intertie of two AC grids that are not otherwise synchronized, and to take advantage of "earth return" paths when necessary to double the capacity of the line. The latter you may need to consider just to make the line cost effective over an equivalent AC span.

Re: Data centers are transitioning from AC to DC

#96

Post by jacquesm »

bigiain wrote: post #79
jacquesm wrote: post #67

Earlier quoted context omitted.

You got super lucky.

Yep. Super super lucky. I suspect my reading glasses are the only reason I can still see anything.

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.

Re: Data centers are transitioning from AC to DC

#98

Post by jacquesm »

manwe150 wrote: post #93
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 suppose that still begs the question somewhat, since the US does have 240V (2 phase) already driving many appliances. Why hasn’t it ever become standard for luxury kitchens to have a European-style outlet for use with a European kettle? I know the US already has a different 240V plug shape, so it might have to be an unlicensed installation, but surely someone wanted hot tea faster and did that calculus before?

Well, as you say, it would not be according to code and the insurance company might have something to say about it. It's also single phase but not quite the way you do it in the USA, it would be a neutral and a phase whereas in the USA I think it is 2x110. Finally, it's 50 Hz rather than 60 which would work fine for resistive loads but not so well for inductive ones such as transformers and motors.

In all likely not worth the trouble. When I moved to Canada I gave away most of my power tools for that reason and when I moved back I had to do that all over again.

Re: Data centers are transitioning from AC to DC

#99

Post by adgjlsfhk1 »

arijun wrote: post #38
adgjlsfhk1 wrote: post #19

Earlier quoted context omitted.

AC is less efficient than DC at a given voltage. The advantage of AC is that voltage switching is cheap, easy and efficient. Switching DC voltage is way harder, more expensive, and less efficient. However the switching costs are O(1) and the transmission losses are O(n) so for some distance (currently somewhere around 500 km) it's worth paying the switching cost to get super high voltage DC. The big thing that's chan…

> AC is less efficient than DC at a given voltage To expand on this, a given power line can only take a set maximum current and voltage before it becomes a problem. DC can stay at this maximum voltage constantly, while AC spends time going to zero voltage and back, so it's delivering less power on the same line.

this iirc is the smallest of 3 problems. the other 2 are skin effect (AC wires only store power on the outside of the wire) and capacitive effects (a write running parallel to the ground is a capacitor and AC current is equivalent to constantly charging and discharging the capacitor)

Re: Data centers are transitioning from AC to DC

#100

Post by defrost »

pocksuppet wrote: post #86
scheme271 wrote: post #73

Earlier quoted context omitted.

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?

Ruins the fun and interrupts instilling respect deep into the bones of interns.

Allegedly

While on "work experience" from high school I was put on washing power lines coming straight out of the local power station near the ocean - lots of salt buildups to clear.

Same deal, flashover suits and occasional arcs .. and much laughter from the ground operators who drifted the work bucket close.

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