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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

#161

Post by eszed »

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…

I lived in a 19th century house in San Francisco that had gorgeous plaster work medallions on the ceilings - think cherubs and fruits - in the middle of which were the light fixtures. One day my dumb-ass flatmate made an ill-advised attempt to DIY his light fixture and cracked the still-active gas line embedded in the ceiling. Sometime in the 1920s - the date was printed on a sticker in the electrical panel - when they electrified the house, they'd wrapped the electrical wires around the gas pipes, and left them otherwise in situ. Crazy stuff.

Re: Data centers are transitioning from AC to DC

#162

Post by fc417fc802 »

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?

Ahckhually US residential is split single phase, not two phase. https://en.wikipedia.org/wiki/Split-phase_electric_power

I think the answer to your question is that it mostly doesn't matter for personal mug size quantities of hot water and if it does matter to you there are readily available competing options such as dedicated taps for your kitchen sink.

Perhaps the biggest reason is that a traditional kettle on any half decent electric range will match if not exceed the power output of any imported electric kettle. Many even go well beyond that with one burner marked "quick boil" or similar.

Re: Data centers are transitioning from AC to DC

#163

Post by beAbU »

aaronbrethorst wrote: post #138
chrneu wrote: post #104

Earlier quoted context omitted.

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…

We’re talking about Nikola Tesla, not Elon Musk, and I don’t think Musk is gay.

I think you need to read the post you are responding to again.

Re: Data centers are transitioning from AC to DC

#164

Post by beAbU »

idiotsecant wrote: post #65
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.

I still have a bunch of 48vdc comms gear in my powerplant.

Why do you have a powerplant?

Re: Data centers are transitioning from AC to DC

#165

Post by fc417fc802 »

flowerthoughts wrote: post #149
adrr wrote: post #23

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

I'm renovating a house, and have been considering 24V or 48V DC outlets in a few rooms. Semiconductors become more expensive above ~32V, so 24V might be the sweetspot. However, there's also PoE (24 or 48V!), so maybe that's the right approach. It's not like each outlet is going to run a heater anyway.

Lower voltage makes voltage drop across the line proportionally worse. Depending on the purpose PoE is probably the way to go since the wiring and hardware is all standardized and safety certified.

Unless you mean running AC and installing inverters in the wall? What is this even for? All my electronics are DC but critically they all require different voltages. The only thing I might benefit from would be higher voltage service because there are times that 15 A at 120 V doesn't cut it.

Re: Data centers are transitioning from AC to DC

#167

Post by elcritch »

qingcharles wrote: post #129
MathMonkeyMan wrote: post #42

Earlier quoted context omitted.

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…

I discovered the same exact thing wiring a second phone line to my bedroom as a teenager. I jumped into a pile of fiberglass insulation! :/

Re: Data centers are transitioning from AC to DC

#168

Post by elcritch »

throw0101d wrote: post #22
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.

> 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. IEEE 802.3bt can deliver up to 71W at the destination: just pull Cat 5/6 everywhere. * https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_i... * https://www.usailighting.com/poe-lighting

And pay $60 per Ethernet POE+ light bulb.

Re: Data centers are transitioning from AC to DC

#169

Post by torginus »

adiabatichottub wrote: post #81
torginus wrote: post #69

Earlier quoted context omitted.

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.

I mean, most AC circuit breakers use electromagnets to trip on overcurrent (as well as bimetallic strips using thermal methods for sustained high current).

Electromagnets dont work for DC, so your breaker will never trip. For thermal protection, you need current, so that checks out, and it would make sense for it to be rated under 50V as thats considered the highest voltage thats not life threatening on touch.

PV Batteries in general have a very high current (100s of A) at ~50Vish volts, so I dont think there's a major usecase for using household breakers for them.

Im still not getting your point BTW, switches and breakers are two separate things, with different workings, and household (and datacenter) DC would be I think around 400ish V, which is a bit higher than the peak voltage of AC, but still within the arc limits of household wiring (at least in 230V countries).

The advantage of DC is that you use your wiring more efficiently as the mean and peak wattage is the same at all times. Going with 48V would mean high resistive losses.

Re: Data centers are transitioning from AC to DC

#170

Post by AndrewDucker »

ta9000 wrote: post #160
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…

Does that mean when we run out of Ga there are no more LED TVs?

Why would we run out of Ga?
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