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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

#421

Post by shiroiuma »

fragmede wrote: post #398
shiroiuma wrote: post #397

Earlier quoted context omitted.

>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? I've heard of Americans getting EU plugs for things like this, but it's extremely uncommon. The simple answer is: Americans…

If speed is the issue, Japanese water boilers keep water at or near boiling so there's less of a wait, and they operate on 110v.

These make absolutely no sense and are extremely wasteful if you're only making 1 or 2 cups of tea per day. They make a lot of sense if you're in an office full of tea-drinkers though. Home users are more likely to be in the first group.

Re: Data centers are transitioning from AC to DC

#422

Post by shiroiuma »

matt-p wrote: post #404
shiroiuma wrote: post #378

Earlier quoted context omitted.

Large home appliances probably mostly need DC power these days too. Look at clothes washers: they all have variable-speed reversing motors, so they're probably using brushless DC motors (which use motor drives that are fed with DC, and output variable-frequency and variable-amplitude sinusoidal waves to drive the motor). HVAC seems to be similar, with variable-speed motors and compressors. I don't think that much stu…

[HVAC] true for the fans and controllers but surely you wouldn't DC feed a compressor.

Aren't compressors these days usually variable-speed?

Re: Data centers are transitioning from AC to DC

#423

Post by jacquesm »

swamp_donkey wrote: post #158
jacquesm wrote: post #96

Earlier quoted context omitted.

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.

Ah! Perhaps you are a member of the gigawatt club? Eligible for entry once you have accidentally tripped off 1000 MW of load or generation! No sweeping that under the table

You brought back a memory, a second hand one, but still a great story. A guy I knew long ago had emigrated from NZ to NL. His main claim to fame in NZ was that one day he showed up drunk for work. In itself this wouldn't have been memorable, if it wasn't for his job, which was to manage a relatively small hydro plant on one of three shifts. On that particular day the plant had to be brought back online after being out for service and since it was really old the synchronization was manual. You had to control the flow of the water, monitor two concentric spinning wheels with the one driven by the grid and the other driven by the local genny and when the phase markings were lined up 'just so' you had to engage this frankenstein level switch to couple the grid to the generator and from there on inertia did it's thing so you could open up the gate to allow more water so the generator would start leading the grid effectively generating power.

Any kid could do it. Probably. But not a drunk one and instead of waiting long enough for both wheels to stay synchronized indicating there would be only a small jump in phase he just said f* it and connected the two anyway. Predictably, this led to a serious disturbance to the grid which in turn caused a whole lot of other stuff to disengage. Since his chances for re-employment on account of his new-found fame were somewhat minimal he decided to emigrate instead :)

Re: Data centers are transitioning from AC to DC

#424

Post by the_cosmos »

wat10000 wrote: post #409
the_cosmos wrote: post #399

Earlier quoted context omitted.

Voltage is _always_ relative; you only ever measure differences between two points. Voltmeters have two probes. Ground is just a convenient reference, not a universal zero. And while Earth can act as a reference or return path in some systems, it’s not perfectly neutral or fixed...it’s just large enough to approximate that in practice. (The interplanetary medium aka aether doesn't exist) Objects don’t repel because t…

Can't you define zero as the limit of the potential at infinity? And neutral charge bodies in empty space are generally close to that. The interplanetary medium absolutely exists. I'm not talking about aether. I'm talking about the soup of dust, gas, and particles that fills space in the solar system. It contains a lot of charged particles, which is what keeps Earth extremely close to neutrally charged. Any deviation…

Yeah, I did mistake what you were trying to say. We’re just coming at this from two different sides... physics does have the convention that absolute zero potential is defined at infinity. I was looking at it strictly from a practical circuit perspective, where 'zero' is just wherever we stick the ground probe, and we only ever calculate for the relative deltas. And we generally don't have wires that can make it to the interplanetary medium or the edge of the infinite ground plane :)

Re: Data centers are transitioning from AC to DC

#425

Post by anonymousiam »

fsh wrote: post #155
anonymousiam wrote: post #123

Earlier quoted context omitted.

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 fr…

Essentially none of this is true. The war of the currents was between Edison and Westinghouse, not Tesla. Tesla's downfall was that he turned into a crackpot who rejected modern science, such as Maxwell's equations, and started defrauding investors. Edison was an outspoken opponent of the death penalty, and the electric chair used AC simply because it is much more deadly.

Westinghouse was using Tesla's patents. Get your facts right.

Every so often, I see or hear a new narrative of history that does not align with reality. I used to wonder how this could happen, but one of my sons explained to me that in his college history courses (in multiple accredited universities), the professors would teach their version of history, using their notes as the course material. They circularly cite other like-minded revisionist material, and most of their students just accept what the professor says as fact. He has seen this again and again in both lower and upper division courses.

This is a disturbing trend, and aside from "woke culture" indoctrination, I don't know what's behind it, or why these professors are not held to basic academic standards.

https://geekhistory.com/content/george-westinghouse-used-tes...

Re: Data centers are transitioning from AC to DC

#426

Post by anonymousiam »

HWR_14 wrote: post #152
anonymousiam wrote: post #123

Earlier quoted context omitted.

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 fr…

Edison did not invent the electric chair. When the inventors were trying to choose between using AC or DC he helped them decide on AC as part of his PR campaign.

These (and many other) sources cite Edison funding a campaign to use AC to electrocute animals, to show that it was more dangerous than DC.

https://www.energy.gov/articles/war-currents-ac-vs-dc-power

https://www.discovermagazine.com/the-cruel-animal-testing-be...

Re: Data centers are transitioning from AC to DC

#427

Post by wat10000 »

the_cosmos wrote: post #424
wat10000 wrote: post #409

Earlier quoted context omitted.

Can't you define zero as the limit of the potential at infinity? And neutral charge bodies in empty space are generally close to that. The interplanetary medium absolutely exists. I'm not talking about aether. I'm talking about the soup of dust, gas, and particles that fills space in the solar system. It contains a lot of charged particles, which is what keeps Earth extremely close to neutrally charged. Any deviation…

Yeah, I did mistake what you were trying to say. We’re just coming at this from two different sides... physics does have the convention that absolute zero potential is defined at infinity. I was looking at it strictly from a practical circuit perspective, where 'zero' is just wherever we stick the ground probe, and we only ever calculate for the relative deltas. And we generally don't have wires that can make it to t…

Space is only ~60 miles away, that's not that much wire. Getting one end up there is left as an exercise for the electrician....

I think it all ties together. Ground potential as in sticking things in the actual ground is in practice pretty much the same as that theoretical potential at infinity, because space has enough charged particles flying around to equalize the imbalance. But it doesn't really matter from a practical perspective when making circuits.

Re: Data centers are transitioning from AC to DC

#428

Post by pdpi »

kjs3 wrote: post #410
Brian_K_White wrote: post #382

Earlier quoted context omitted.

And in normal use, how often do you handle or cycle an rj45 vs a usb? Even when it's your job the usb are still handled and cycled way more often. You might handle 100 ethernet jacks today, but it won't be the same one 100 times. You plug it in and don't touch that one again for 5 years.

You mean the ethernet cable in my laptop? Couple of times a day. The box under my desk? Often? How about the hundreds of devices I work with that have RJ45 connectors for serial access? All the time? Are you seriously telling me you hold up a (decently made) ethernet cable next to a USB-C connector and think "yeah...the one a fraction of the size of the other is obviously mechanically stronger". Is this some Apple sh…

No, but looking at the two side by side, I do think that the one with a fragile clip that shears off every time somebody trips on it is going to be more of a problem than the friction fit one that will just come off.

Re: Data centers are transitioning from AC to DC

#429

Post by idiotsecant »

beAbU wrote: post #164
idiotsecant wrote: post #65

Earlier quoted context omitted.

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

Why do you have a powerplant?

Because I am an electrical engineer in a powerplant and I am responsible for those systems.

I don't own it personally, I say it in the same sense someone says 'my building' when they mean 'place my apartment is at'

Re: Data centers are transitioning from AC to DC

#430

Post by Animats »

dotancohen wrote: post #385
t0mas88 wrote: post #300

Earlier quoted context omitted.

EV chargers take a different approach. There is no power on the connector while you're plugging it in. It then locks in place before the contactor closes and power is delivered. Unplugging is the same, power is removed before the plug is unlocked for release.

Do the EV chargers not have an alternative disconnect sequence for when the two sides are forcibly mechanically separated? Either by accident, malicious intent, or mechanical failure of some component.

Yes. See UL 2594.[1] There's a lot of monitoring on those things, plus regular circuit breakers and GFCIs.

[1] https://www.intertek.com/batteries/automotive-battery-ev-tes...

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