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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

#11

Post by arijun »

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…

Surely if it makes sense for the big players, they will do it, and then the benefits will trickle down to the rest? Like how Formula 1 technology will end up in consumer vehicles.

Re: Data centers are transitioning from AC to DC

#12

Post by adamking »

shdudns wrote: post #3

How is DC better than a three phase delta 800Vrms, at 400Hz? - Three conductors vs two, but they can be the next gauge up since the current flows on three conductors - no significant skin effect at 400Hz -> use speaker wire, lol. - large voltage/current DC brakers are.. gnarly, and expensive. DC does not like to stop flowing - The 400Hz distribution industry is massive; the entire aerospace industry runs on it. No ne…

> no significant skin effect at 400Hz -> use speaker wire, lol

now run that unshielded wire 50 meters past racks of GPUs and enjoy your EMI

> The 400Hz distribution industry is massive; the entire aerospace industry runs on it

nothing in that catalog is rated for 100kW–1MW rack loads at 800Vrms

> 3 phase @ 400Hz is x6 = 2.4kHz... Your PSU is now 14 diodes and a ceramic cap

you still need an inverter-based UPS upstream, which is the exact conversion stage DC eliminates

> large voltage/current DC breakers are.. gnarly, and expensive. DC does not like to stop flowing

SiC solid-state DC breakers are shipping today from every major vendor

> DC-DC converters are great, but you're not going to beat a transformer in efficiency or reliability

wide-bandgap converters are at 95%+ with no moving parts

Re: Data centers are transitioning from AC to DC

#14

Post by arijun »

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).

Re: Data centers are transitioning from AC to DC

#15

Post by cjbgkagh »

sghiassy wrote: post #13

I’ve always wondered about these new High-Voltage DC (HVDC) transmission lines. I always thought AC’s primary benefit was its transmission efficiency?? Would love to learn if anyone knows more about this

https://en.wikipedia.org/wiki/High-voltage_direct_current

Re: Data centers are transitioning from AC to DC

#16

Post by bluGill »

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.

Re: Data centers are transitioning from AC to DC

#17

Post by umvi »

I don't understand why new houses don't just have one high quality AC/DC converter so you can just use LED lighting without every bulb needing its own AC/DC converter. I imagine the light bulb cartel wouldn't really like that.

Re: Data centers are transitioning from AC to DC

#18

Post by bluGill »

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…

Tesla also design the modern induction motor which needs ac. Though these days we often run them on a phase generator which has a dc step.

Re: Data centers are transitioning from AC to DC

#19

Post by adgjlsfhk1 »

sghiassy wrote: post #13

I’ve always wondered about these new High-Voltage DC (HVDC) transmission lines. I always thought AC’s primary benefit was its transmission efficiency?? Would love to learn if anyone knows more about this

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 changed in the last ~30 years is a ton of research into high voltage transistors, and fast enough computers to do computer controlled mhz switching of giant high power transistors. These new super fancy switching technologies brought the switching costs down from ludicrous to annoyingly high.

Re: Data centers are transitioning from AC to DC

#20

Post by bluGill »

umvi wrote: post #17

I don't understand why new houses don't just have one high quality AC/DC converter so you can just use LED lighting without every bulb needing its own AC/DC converter. I imagine the light bulb cartel wouldn't really like that.

It wouldn't work. leds need low voltages, meaning massive wires. you can run the voltage change on ac or dc. Ac just needs a few capacters to smooth the wave out.
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