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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

#121

Post by teleforce »

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…

>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.

This!

The soon people realized these facts the better. The pervasive high rise buildings did not happen before the invention of modern cranes.

Exactly twenty years ago I was doing a novel research on GaN characterization, and my supervisors made a lot money with consulations around the world, and succesfully founded govt funded start-up company around the technology. Together with SiC, these are the two game changing power devices with wideband semiconductor technology that only maturing recently.

Heck, even the Nobel price winning blue LED discovery was only made feasible by GaN. Watch the excellent video made by Veritasium for this back story [1].

[1] Why It Was Almost Impossible to Make the Blue LED:

https://youtu.be/AF8d72mA41M

Re: Data centers are transitioning from AC to DC

#122

Post by adiabatichottub »

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.

Maybe if by "same voltage" we mean DC voltage the same as AC peak voltage. When we talk about AC voltage we are referring to root-mean-square (RMS) voltage. It's kind of like saying the average, though for math reasons the average of an unbiased sine wave is 0. Anyhooo, 1 VRMS into a load will produce the same power as 1VDC. If AC delivered less power than DC at the same voltage then life would be very confusing.

Re: Data centers are transitioning from AC to DC

#123

Post by anonymousiam »

chrneu wrote: post #104
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…

the internet really needs to stfu about tesla and get over that oatmeal comic that spawned a billion internet myths. dude was a decent inventor but suffered from chronic mental health issues and, in his lifetime, wasted so much time/energy/money and burned so many bridges with his horrible attitude. there's a reason most people didnt like him in his day, he was a depressed asshole who alienated everyone around him, a…

Tesla was an outstanding technologist, but a poor businessman. He had a "vision" (actually more than one) about how his ideas could transform the world. Some of his ideas were amazing, but he was swindled out of his patents because the investors knew he had a passion and wanted to see them in use. The polyphase AC motor or fluorescent light bulb could have made him millions.

IMHO, the vision he had about universal free electricity (transmitted wirelessly) was the dumbest. It was a novel idea, and he invested a lot (his time and other people's money) in it. The problem with his idea is that there was no way to monetize it (and profit from it). (There were also the technical issues of the power loss over distance (1/R^2), the harm to the environment, and the interference with radio communications.)

Edison was quite a villain. He stole many of his "inventions", and orchestrated a PR campaign against Tesla touting the "evils" of AC power. AFAIK, the electric chair was either invented or inspired by him.

I know these things because I've read many books on various topics related to Tesla, and all of this knowledge predates the Internet.

Re: Data centers are transitioning from AC to DC

#124

Post by _fizz_buzz_ »

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...

Obviously 48VDC has been around and internally they will probably still step down to 48V. But these 48V islands are nowadays inter connected by regular AC grid. They want to replace that interconnection with a 800VDc bus. I kind of assume they chose 800vdc because there are already bunch of stuff available from EVs which also have 800vdc battery packs now.

Re: Data centers are transitioning from AC to DC

#125

Post by adiabatichottub »

jacquesm wrote: post #113
bigiain wrote: post #101

Earlier quoted context omitted.

You're _so_ right! I'm pretty sure you have my delivery address from when I bought sorted Lego from you about 10 years back. Let me know when to expect the 100,000Amp test equipment! I shall make sure I wear better PPE than just my reading glasses. :-)

This would be the funniest thing to do. 100K Amps is doable, the question is for how long. That would be one very impressive bank of capacitors. And to turn a 00 into plasma would have some spectacular side effects, such as raining molten copper across a sizeable area. Just your reading glasses would indeed not be enough, there probably isn't any PPE that I would consider entirely safe other than sufficient distance…

Ho ho ho, you asked for it:

https://www.youtube.com/watch?v=OC7sNfNuTNU

Re: Data centers are transitioning from AC to DC

#126

Post by aidenn0 »

mjuarez wrote: post #35
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.

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.

RTL and DTL both needed negative-voltage relative to ground, as do many analog circuits.

Re: Data centers are transitioning from AC to DC

#127

Post by mcbishop »

teleforce wrote: post #121
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…

>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. This! The soon people realized these facts the better. The pervasive high rise buildings did not happen before the invention of modern cranes. Exactly twenty years ago I was doing a novel res…

I've heard the EV charging has played a big role in the maturation of GaN / SiC.

Re: Data centers are transitioning from AC to DC

#128

Post by aidenn0 »

jacquesm wrote: post #98
manwe150 wrote: post #93

Earlier quoted context omitted.

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…

> 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.

If you ever have to do it again, you can probably get a transformer rated high enough for power-tools for cheaper than replacing all of your power tools.

Re: Data centers are transitioning from AC to DC

#129

Post by qingcharles »

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…

It's a pretty decent chunk of power down a POTS cable too, as it was designed to ring multiple big chunky metal bells in the days of yore.

I was wiring in a phone extension for my grandma once as a boy and grabbed the live cable instead of the extension and stripped the wire with my teeth (as you do). I've been electrocuted a great number of times by the mains AC, but getting hit by that juicy DC was the best one yet. Jumped me 6ft across the room :D

Re: Data centers are transitioning from AC to DC

#130

Post by teleforce »

mcbishop wrote: post #127
teleforce wrote: post #121

Earlier quoted context omitted.

>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. This! The soon people realized these facts the better. The pervasive high rise buildings did not happen before the invention of modern cranes. Exactly twenty years ago I was doing a novel res…

I've heard the EV charging has played a big role in the maturation of GaN / SiC.

Yes, EV and high frequency electronics (microwave, mmWave, photonics) that require very fast switching capability.
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