281–290 of 432 posts
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> If there was anything like a high power transistor back then he would have used that. Mercury arc rectifiers were used long before his death.
Yes, but a rectifier only rectifies . That's not going to give you DC-DC conversion - let alone converting it to a higher voltage for long-distance transmission.
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…
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Yes, I read that. There had better be a backup system. MOSFETs tend to fail ON, and there's a megawatt going into each rack. Somehow this seems the wrong approach to AI.
Fail spectacularly Data center workers are gonna need those big yoink sticks and those thick arc-fault bibs that furnace operators wear.
It's not that bad. It's just ordinary industrial protective gear.
[1] https://www.mcmaster.com/products/arc-flash-protection-face-...
[2] https://www.mcmaster.com/products/electrical-protection-glov...
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Something to consider, and something I got a vivid demonstration of while playing with solar panels, DC arcs aren't self-extinguishing, unlike AC arcs. At one point I stuck a voltage probe in, and the arc stuck with it as I pulled the probe away. It also vaporized the metal tip of the probe. My understanding is that DC breakers are somewhat prone to fires for this reason, too.
> My understanding is that DC breakers are somewhat prone to fires for this reason, too. I think its that DC breakers are more expensive, so people use AC rated breakers instead. They are both rated for 400v @10 amps, its the same thing right? It turns out they are not, and most people, even electronics types rarely play with 200v+ of DC.
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…
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Sidenote: Whenever someone tells you that (vital) reserves of some ressource are going to run out soonish (implying drastic consequences), you should be extremely skeptical: Such predictions have an abysmal historic track record, because we tend to find workarounds both on the supply side (=> previously undiscovered reserves) as well as flexibility on the demand side (using substitutes). This applies historically for…
> Such predictions have an abysmal historic track record, because we tend to find workarounds both on the supply side (=> previously undiscovered reserves) as well as flexibility on the demand side (using substitutes). That's a classic example of the "preparedness paradox" [1]. When no one raises the alarm in time or it is being ignored, resources can go (effectively) exhausted before alternatives can be found, or co…
Yes we can run out of oil, but nobody really knows if or even when that will happen. Right now I'm guessing we won't run out because wind and solar is so much cheaper for most purposes everyone is shifting anyway - this will take decades to play out.
Installing a ceiling fan used to be treacherous and so heavy. Also loud and buzzy after installed. Now the fans in these things are so lightweight and easy.
seeing the same in many more areas (lighting, etc)
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Because the chassis is connected to ground (as in, a literal grounding rod hammered into the soil) and by definition your 0V reference point. The crucial difference is the direction in which the current is flowing: is it going "in to", or "out of" a hot wire? This becomes rather important when those wires are leaving the building and are buried underground for miles, where they will inevitably develop minor faults. W…
So, there is a true value for 0? Does that mean when you have electronics and use multiple dc-dc converters all the inputs and outputs share the same ground, it's not just the values for that pair of wires? And if I want to use a telephone on an incorrectly wired 48dc circuit, I could switch the positive and negative wires, as long as the circuit in the telephone is isolated and never touches ground? Thanks. Somehow…
I think a circuit should mostly care about the deltas, but when you’re talking about things like phone lines, the earth becomes part of your circuit. You can’t influence its potential (it’s almost exactly neutral because any charge imbalance gets removed by interaction with the interplanetary medium) so everything else is going to end up being determined by what you need for their relative potential to that.
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> DC will creep much easier than AC Can you say more about "creep"? Is the resistance changing? Or is material actually migrating? Also curious why it's worse using DC.
https://www.eevblog.com/forum/beginners/understanding-high-v...
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> If you went 48 straight to POL voltages then you would have horrific converter performance. What's horrific converter performance in numbers? An isolated flyback (to 12V) should be able to hit >92% and doesn't care if it's fed -48V or +48V or ±24V. TI webench gives me 95% though I'd only believe that if I'd built and measured it. What's the performance of your -48V → +48V? [with the caveat that these frequently req…
-48 to 48 claims something like 97% (load dependent of course). It also needs to arbitrate between two input supplies for glitchless redundancy, plus have PM bus and other spec mandated stuff. There is no technical reason why you cant go -48 -> 12 as you state with good efficiceny, but we cant get hold of a part that ticks all the boxes. Horrific performance by my definition would be 48v to say 1v. We only realistica…