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Power Hardware

Are Data Centers Finally Ready For DC Power? 462

Posted by samzenpus
from the edison-wins-again dept.
1sockchuck writes "It's been five years since a landmark study outlined the potential benefits of DC power distribution in data centers. But adoption of DC in data centers remains limited, even as the industry aggressively pursues a wide array of other energy savings strategies. Advocates of DC distribution are hoping a new study will jump start the conversation about DC distribution, which can save energy by eliminating several wasteful AC-to-DC conversions within a data center. Meanwhile, an industry association for DC power adoption, the EMerge Alliance, has formed a new technical standards committee for data centers, and is advancing a 380-volt DC power standard. Will DC distribution ever gain momentum in data centers?"
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Are Data Centers Finally Ready For DC Power?

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  • by ravenspear (756059) on Wednesday November 30, 2011 @04:43PM (#38219358)

    I told you bitches I would prevail one day!

    • by rolfwind (528248) on Wednesday November 30, 2011 @04:51PM (#38219476)

      Not really. AC was the answer to how to transport electricity long distances.

      Currently, it is still converted to DC in a huge amount of devices, in the computer at the PSU. Few devices use AC iirc, something like a fan/ceiling fan probably has an AC motor because a DC motor would slice your finger off if you decided to play with the blades. So, the question then just remains how to optimize the point of conversion. It's rather like the electric car-fossil-fuel-electric-plant/gasoline car debate: have a bunch of small inefficient combustion engines or a large efficient one but deal with transport losses (along with a bunch of other issues).

      In this case, just where along the line do you convert the AC to DC. Since DC can't really travel far at all without significant losses, I guess that would be at the rack level?

      • by Wonko the Sane (25252) * on Wednesday November 30, 2011 @04:57PM (#38219578) Journal

        AC was the answer to how to transport electricity long distances

        AC was used because using transformers to convert between voltage levels was more efficient than motor-generators and solid state electronics hadn't been invented yet. All other things being equal, DC is always more efficient than AC for long distance transmission.

      • by Elder Entropist (788485) on Wednesday November 30, 2011 @05:04PM (#38219718)
        Very high voltage was the answer to how to transport electricity long distances. AC was the answer to how to convert that high voltage to safer/useful low voltages cheaply. Very high voltage DC can lose less power over distance than AC. On smaller/cheaper wires too due to the AC skin effect.
        • by afidel (530433)
          That's only true with very expensive solid state components that didn't exist when the decision to go AC was made and it also ignores the fact that DC branching is extremely complex so it only works when you are moving power from generation site to large single use site, a wider grid is much harder to do with DC.
        • Re: (Score:3, Informative)

          by bkcallahan (2515468)
          A/C skin effect applies *based on frequency*; I assure you skin effect at 50/60Hz, even at high voltages, is negligible -- Doesn't matter if it's 420kV or 4.2V. A circuit at 29.350 MHz at low voltages has to worry a LOT more about it than a 50/60Hz line voltage. (And it really starts kicking off at the start of the microwave range, 300MHz, and is exceptionally important by the end of the microwave range 3GHz.) The reason A/C is used is based off of Ohm's law and is based on current and resistance; Jack u
      • by Mr Z (6791) on Wednesday November 30, 2011 @05:05PM (#38219738) Homepage Journal

        The problem with DC back in Edison's day was that you couldn't easily step it up or down. DC doesn't have higher losses than AC at the same voltage. In fact, DC radiates less energy away than AC does, and is therefore more efficient [wikimedia.org].

        Ohmic losses all come down to I^2 * R. R is the resistance of the cable, and I is current. To deliver a given amount of power, you have to have a certain V*I. To reduce Ohmic losses, then, you have to reduce the amount of current, which means going up in voltage.

        Incidentally, that's also what's driving automobile manufacturers toward 48v instead of 12v [automotive-eetimes.com], since it would cut the current from the battery by a factor of 4, thereby reducing the amount of loss in the wiring by a factor of 16. That means you can use smaller wires to deliver the same amount of power, safely.

        • Re: (Score:2, Interesting)

          by Anonymous Coward

          It's not only the radiation that makes AC less efficent. It is also how you can build conductors.

          If you built just a simple very long cylinder out of copper, it is the perfect conductor for DC. For AC only the border is used, as the electric field presses electrons there. So with AC you have to use complex cables working around this, while with DC you get better behaviour with a simpler and less expensive design.

          You won't get that for small voltages. But for the big power lines going long distances, this is

        • by ssyladin (458003)

          As an aside, car manufacturers are also moving towards higher voltage because that gives them easier access to drive high-power systems like power steering. Currently most power steering is pneumatically driven, which comes with a hefty overhead cost in terms of manufacturing and maintenance. With a high-voltage bus to drive it, the complex machinery simplifies it to an electric motor and some gears.

        • The problem with DC back in Edison's day was that you couldn't easily step it up or down.

          There's also the problem that, at reasonable transmission voltages, if you shock yourself on 60Hz AC, you're likely to spasm off the terminals within a few cycles, but a DC shock is more likely to cause your muscles to lock you onto the source where you will stay until fried extra crispy, unless helped off by a bystander.

      • by khallow (566160) on Wednesday November 30, 2011 @05:06PM (#38219754)

        Since DC can't really travel far at all without significant losses, I guess that would be at the rack level?

        Transmission losses are actually less than for AC. They don't lose energy to inductance with nearby conducting loops and impedance losses are about the same as for a three phase line with same RMS voltage. The real problems are conversion to and from AC, and the fact that DC operates at a much lower voltage (low voltage results in high losses, whether AC or DC) when in actual servers.

        The idea behind DC powered centers is that the AC to DC conversion is done in one place, away from the servers so that a) the heating load of the center is lower, and b) it can be done in one place with a relatively efficient converter rather than in a thousand places with less efficient designs. The accompanying baggage as I gather is that you're either running a lot of power-losing low voltage lines or doing some sort of power-losing DC voltage step down inside the center.

        • The typical computer power supply and almost everything else anymore uses a rather efficient switching power supply, it takes the input power, rectifies it, runs it through a transformer by switching the DC on and off at high frequency, then rectifying the output from the transformer to supply the rest of the computer. The power supplies change from 115 VAC to 230 VAC input by a simple switch, the 230 VAC , which has a peak to peak voltage of 325 volts, just a stones throw from 380 VDC. The only reason that

      • by EETech1 (1179269) on Wednesday November 30, 2011 @05:39PM (#38220290)

        That's why they use 380 volts! One big splice goes to all the 12 volt stuff, then another splice comes off of that splice to do the 5 volt stuff. It is not run through regulators, it just happens automatically due to the superior characteristics of DC power! They also tap into the ground wire at various places to get the -5 and -12. Magic I tell ya!

        It sees it's best efficiencies running near 100% utilization through so you want to plan your workloads accordingly, or you risk watching your $#!+ let out it's magic smoke! So all in all it should drive down the price of "the cloud" by forcing competition!

        Win, Win!

    • by WaffleMonster (969671) on Wednesday November 30, 2011 @07:22PM (#38221128)

      I told you bitches I would prevail one day!

      There seems to be a popular/fundemental misunderstanding of the tesla/edison debate.

      DC is MORE effecient on the wire than AC given the same voltage, amperage and wire gauge.

      The reason for this is in AC systems eddy currents induced by changing electric fields at 50/60hz cause electrons to migrate away from the core effectivly reducing wire size.

      Why AC has been the choice for so long is an engineering problem.

      Building rectifiers to convert AC to DC from huge AC generators which produce virtually all of our electricity with the kinds of voltages needed to carry massive quantities of volumes of energy is difficult, unreliable and ineffecient..even today.

      Back then it was practically impossible. The choice between Tesla and Edison really boiled down to high vs low voltage. Low voltage transmission required impossible quantities of copper or decentralized generation.

      Tesla wanted larger more centralized generation which given what we use for fuel these days is an exceedingly smart move.

  • by Anonymous Coward on Wednesday November 30, 2011 @04:44PM (#38219368)

    How many little wall-warts does the average house have? Tens? We need low voltage DC in our houses, and standardize all the little widgets on one of (say) two voltages. Each outlet could supply them in a dedicated connector alongside the current AC.

    • Re: (Score:2, Insightful)

      You've apparently never ran electrical wire in the home nor understand why that would be a completely insane idea.
      • by LehiNephi (695428) on Wednesday November 30, 2011 @04:58PM (#38219602) Journal
        I do/have done both (run electrical and understand the implications), and GP has a point. When I think of the things in our house that *must* run on AC, it's only our fridge, freezer, and HVAC. Everything else in the house either converts it to DC or could run quite happily on DC. For certain you'd want to have a different kind of plug for DC devices, but even that would give us an opportunity to 1) standardize on one global plug standard, at least for DC, and 2) allow us to design a small, rugged, safe type of plug.

        Or is there some implication that I'm missing, and that you decided not to point out, in favor of flaming GP?
        • by vlm (69642) on Wednesday November 30, 2011 @05:05PM (#38219724)

          For certain you'd want to have a different kind of plug for DC devices, but even that would give us an opportunity to 1) standardize on one global plug standard, at least for DC, and 2) allow us to design a small, rugged, safe type of plug.

          Aka the famous (in some circles) Anderson Power Pole. Go ask a ham radio guy.

          The thing I love about in house DC distribution, which I have in my house, is it forces at least a token effect at "green power reduction". Suddenly given the choice of a 12 volt 6 watt LED fed by $2 of small gauge wire vs something resembling welding cable wire to run a 200 watt halogen, you make the ecologically correct choice.

          I used to use cast off surplus 200 watt desktops for my mythtv frontends. Unholy pain to run on 12 V. Now I use 5 watt Zotac boxes. Good for everyone in every way.

        • by nschubach (922175)

          What bothers me is all the new LED bulbs that have transformers in them (guessing, because they get hot! ... feels like wasted energy) to power the LED bulbs when you could have just run a 12VDC line and powered them all on a central transformer like garden lights. I'd think it would be more efficient to run DC to lighting and certain outlets like those where small devices would sit (with standard plugs as you mention) and keep 112-120VAC for things like the appliances.

          You could also centralize a backup ba

          • by Obfuscant (592200) on Wednesday November 30, 2011 @05:57PM (#38220506)

            What bothers me is all the new LED bulbs that have transformers in them (guessing, because they get hot! ... feels like wasted energy)

            High power LEDs get hot because you are running good amounts of current through them, not because there is a transformer. Transformers are pretty much useless with the DC current that runs LEDs.

            I'd think it would be more efficient to run DC to lighting and certain outlets like those where small devices would sit ...

            The problem comes in deciding what voltage to use. 12V means you need rather hefty wires to get the required current for some devices. A 6W LED needs half an amp at 12V. If you use a voltage that makes the current resonable, then you need to convert that voltage to what your device needs, every place you have a device.

            Sending 380V means you can use the same or smaller wires than you'd use for 120V systems, but you'll be busy converting that 380V DC to 12V DC or 5V DC or 1.2V DC -- and while DC-DC conversion has gotten a lot better, it is still more complicated than a simple transformer.

          • by c++0xFF (1758032)

            Well, it's not exactly a transformer, but you're essentially correct -- a high-power LED bulb needs to be supplied its forward voltage at a constant current, which means rectifying and bucking the voltage down. There's lots of schemes to do this, some more efficient than others. The current limiting resistor scheme most of us are familiar with is about the most inefficient way, but it's also very inexpensive. LDOs and linear regulators are still very inefficient. Buck converters are better, but very exp

        • All AC appliances and DC power adapters use a standard voltage of 110v in US/Canada/etc., 220v in other parts of the world (UK/etc.). To implement DC in the house, you would either have to standardize on a specific DC voltage or create a smart power standard (i.e. similar to POE for network gear). Today, most devices that require AC/DC adapters, convert to different DC voltages. That being said, most mobile devices have been standardized to the USB standard of 5V.

          • by nschubach (922175)

            There are a lot of different voltages for DC transformers, but taking a look around my house this past year I spotted mostly 12VDC. I had one 20VDC (Laptop) but the rest were 12. In the past, I've seen 6 and 9 volt transformers, but I rarely see these anymore.

        • by amorsen (7485)

          When I think of the things in our house that *must* run on AC, it's only our fridge, freezer, and HVAC

          If your fridge, freezer, and HVAC are halfway decent, they convert to variable-frequency AC. Fixed-frequency AC motors are inefficient unless the load is constant (and load isn't constant in those applications).

      • by AK Marc (707885)
        Then can you explain why running 12VDC along-side 120VAC (assuming they are sufficiently separated/shielded to not induce 120VAC on the DC line) is a "completely insane idea." Just saying "if you knew what you were talking about, you'd know why it's a bad idea, but I'm too stupid to explain why, I can just mock" isn't very useful
        • It's a matter of how many watts you expect to supply and how large the wires must be to supply that power at 12 volts while maintaining the voltage at the outlets within an acceptable range.
  • by Anonymous Coward on Wednesday November 30, 2011 @04:46PM (#38219392)

    DC power is the standard in the telecom industry.

    I design systems based around HP's BladeSystem, and the DC power modules just drop in and go. It's very easy, works great, and most of all, my telecom customers love them.

    • by Shatrat (855151) on Wednesday November 30, 2011 @04:54PM (#38219510)
      I work with DC power in Telecom and it has 3 huge advantages I can think of off the top of my head:

      1) You centralize your rectification. Instead of having hundreds of power supplies running at 80% efficiency, you can have a large rectifier system running at up to 96%.
      2) Lead Acid batteries are hugely more reliable and less expensive than equivalent UPS systems, and provide more holdover time. They're still expensive and finicky, but many times less so than a UPS.
      3) Any old technician with a brain in their head can run DC power feeds to equipment relatively safely due to the low voltages involved. AC power work of any kind should have a qualified electrician involved.

      • by vlm (69642) on Wednesday November 30, 2011 @05:11PM (#38219830)

        4) Done right with a positive ground system, leads to less corrosion problems with outside plant. Admittedly "inside" the data center, if you're got corrosion, you're doin it wrong.

        5) Less AC hum. We had some microwave site to site short hop gear back in ye olde NTSC days that could only be run off battery without 60 hz interference bars on the screen. Not technologically relevant anymore, but the point remains that DC is always going to be cleaner than AC.

        6) Better lightning protection. I'm sure its happened, but I've never heard of losing a telco DC bus. Big conductors, giant batteries across them, lightning is just not an issue anymore at the power level (still need to ground feedlines / waveguide / whatever you've got at home like that)

        7) dump most of the power conversion heat in the battery room where its all built to handle high temp and no one visits (other than occasional battery maint). Cheaper cooling in the data center, data center is somewhat more habitable, etc.

      • I work with DC power in Telecom and it has 3 huge advantages I can think of off the top of my head:
        3) Any old technician with a brain in their head can run DC power feeds to equipment relatively safely due to the low voltages involved. AC power work of any kind should have a qualified electrician involved.

        Short the posts of a car battery, count the number of milliseconds it takes the pliers to be welded to the leads... Then come back here and tell us all about how low voltage is "safe" and requires no qualifications.

      • Any old technician with a brain in their head can run DC power feeds to equipment relatively safely due to the low voltages involved.

        Voltage only determines if it can overcome the resistance of your skin (and maybe clothing). Beyond that, it doesn't matter. Amperage, on the other hand, determines the power -- the amount of damage the current will cause.

        10 milliamps can kill you. But without at least several dozen volts behind it, it won't make it through your body.

        But. Put something nice and conductive (like a tool) across a low-voltage circuit and you'll get an arc from the short. You don't need high voltage with that conductive ma

    • by the linux geek (799780) on Wednesday November 30, 2011 @04:57PM (#38219582)
      Yeah, I've never quite figured out why telecoms have standardized on 48VDC while everyone else completely ignores its existence. Most midrange servers (HP Integrity and Nonstop, iirc most smaller SPARC Enterprise boxes, some commodity stuff) are available in 48VDC configurations, so it's not like there's a lack of hardware for it.
      • by mjwalshe (1680392)
        because telcos have much much more stringent requirements for up time - a major switch failure is a once in a lifetime event for most people - we have had 3 failures for amazon in the last 4 months at work.
        • Oh, certainly. My post was more a question of why everyone else has ignored 48VDC, not why telcos use it.
          • Afaict there are a few issues with 48V DC for a dataceventer.

            1: it's nonstandard (in the computer industry) so you pay a premium for equipment that runs off it and reduce your choice of equipment.
            2: It's lower voltage so for a given level of tolerable loss your cables have to be much bigger
            3: It's DC so it's more prone to arcing making all your switches and protective devices more expensive and basically ruling out the use of plug and socket connections for anything other than final connection of individual

    • by uncledrax (112438)

      ^ This ^
      Although we're a ISP grown from a Telecom.. so we have large DC plants at most of our sites anyway, so for us, it's just asking our vendors for DC options... most vendors DO have DC PSU options.. it's more of a pain to adapt to the annoying 21" 2-post telecom racks we have.. :/

  • by Animats (122034) on Wednesday November 30, 2011 @04:47PM (#38219406) Homepage

    There's no particular reason that 380 VDC distribution should help efficiency. You still need about two more levels of switching power supply before power reaches the ICs.

    Google's proposal that motherboards should need only 12VDC made more sense. Drives already run on 12VDC, and there's already a level of power conversion near the CPU to get the desired CPU voltage. The USB devices do need +5, but a 12VDC to 5VDC switching converter can handle that. And single-voltage power supplies are more efficient and simpler than multi-voltage ones.

    • Wouldn't you just end up putting a switching power supplies elsewhere and create heat problems, then?

      • by compro01 (777531)

        You already do that anyway. Motherboards take most of their power at 12V and regulate it down to what's needed.

        A modern CPU can use up to 65-ish watts, but runs at about 1.5V, so you're needing 43.3 amps of current. You're not going to be running that little voltage and that much current down a reasonably sized wire of any useful length.

        Videocards do the same thing.

    • by Mr Z (6791) on Wednesday November 30, 2011 @05:10PM (#38219812) Homepage Journal

      The current carrying capacity of the wires would need to be about 30 times larger, though, to deliver the same amount of power. That's pretty huge. To go to 12v everywhere, you'd need huge current-carrying wires everywhere (think "as big as your car battery cables or bigger"). To carry 1kW through a 380V line, you only need to handle 2.6A. To carry 1kW through a 12v line, you need to handle 83A. And that's just one beefy server.

      Now think of your house wiring. Outside of your major appliances, where do you see runs higher than 15A or maybe 30A? There's a reason high voltage is good.

    • by mjwalshe (1680392)
      bollocks do you not understand ohms law - running any thing non trivial on 12v dc is a non starter - any telecom engineer will(and thats on 48V have amusing horror stories about near death (if they where lucky) with big dc systems and that is using 48V
    • by amorsen (7485)

      There's no particular reason that 380 VDC distribution should help efficiency. You still need about two more levels of switching power supply before power reaches the ICs.

      It is easier to step down DC than AC. You don't have to contend with keeping current up during the parts of the wave where AC supplies close to zero power. Instead you just chop at a sufficiently high frequency that your ripple current gets sufficiently low.

  • why 380v? (Score:4, Interesting)

    by wierd_w (1375923) on Wednesday November 30, 2011 @04:49PM (#38219430)

    Wouldn't it make more sense to drive at 12v with an insane amperage behind it, than to drive at 380v and garantee the necessity of a voltage regulator rated for high voltages?

    I mean, the whole reason for doing away with ac current was to eliminate the rectifier and regulator circuits, which belch heat into the data center. Using 380v, which no datacenter device that I know of uses natively (well, maybe the innards of a crt, but that's actually much higher than 380v... AND a deadend tech.), seems kinda... well.... unproductive.

    Is it because of impedence problems or something?

    • by bigtrike (904535) on Wednesday November 30, 2011 @04:53PM (#38219500)

      Lower voltages require larger conductors to carry the same current. Copper isn't that cheap.

      • by wierd_w (1375923)

        Skin effect.. that's right.

        But you can get around that with multistranded wire, right? A bundle of 7 small conductors netting the same approximate volume as 1 big conductor has substantially more conduction surface.

        • by nzac (1822298) on Wednesday November 30, 2011 @05:13PM (#38219862)

          No the skin effect is for (High frequency) AC.

          For DC impedance is determined by the material and the cross section area.

          It does make the cables easier to bend though.

          • by wierd_w (1375923)

            *smacks forehead*

            [Note to self: Avoid asking questions about EE, a field you DID NOT take in college, while recovering from a head cold and while under the influence of medication. Seriously, you'll thank me later. There is a reason why the bottle says not to operate heavy machinery. Hint: it also applies to high energy electronic devices.]

        • by pclminion (145572)

          It's not skin effect, it's the fact that P = VI. If the machine draws 500 watts at 12 volts, the current in the conductor must be 42 amps. The power dissipated in the conductor is I^2*R. Suppose you're willing to dissipate 10 watts in the conductor. That means 10 watt = (42 amp)^2*R, which implies the conductor resistance must be 0.005 ohms.

          Suppose that instead you supply the power at 380 volts. The current is now only 1.3 amps. 10 watt = (1.3 amp)^2*R, which means a conductor resistance of 6 ohms, which is

      • by nzac (1822298)

        Lower voltages require larger conductors to carry the same power, (due to I^2*R losses). Copper isn't that cheap.

        FTFY

        Losses in a wire are determined by the current alone.

      • by vlm (69642)

        Lower voltages require larger conductors to carry the same current. Copper isn't that cheap.

        And you're limited on the high end by state electrician licensing boards who require "high voltage license" instead of regular license somewhere around 440 volts to 600 volts. So however cool you think it might be to design your entire infrastructure around 1024 volt DC, the cost of electricians would be much cheaper if you can keep it under 400 volts.

        Obviously there are some states where this doesn't matter, all I can say is I've heard of cutover points of 440 volts, 600 volts, in some weird combination o

    • by DerPflanz (525793)

      High current ('insane amperage') needs very thick cabling. Not very cheap or efficient. For transport, high voltage AC is the best choice. That's why transport networks use that.

      I didn't do the math on DC transport/distribution in datacenters, but it at first glance it does need high voltage for transport, just to keep the cabling anywhere near affordable. Change to lower voltages when needed.

      • by amorsen (7485)

        For transport, high voltage AC is the best choice.

        For transport, high voltage DC is the best choice. No impedance worries, no phase to keep in sync over thousands of km. AC is legacy.

    • Re:why 380v? (Score:4, Informative)

      by Urban Garlic (447282) on Wednesday November 30, 2011 @05:01PM (#38219652)

      Basic Ohm's law -- the resistive loss through a DC wire is the voltage drop across the wire, times the current through the wire. But the voltage drop across the wire is proportional to the current, it's just I*R, so the total power dissipated in the wire itself (i.e. not transferred to the load) is I*I*R. So, you want the current going to the load to be as small as possible. But, of course, the load still needs to get all the power it needs, so the operating voltage (which is distinct from the through-the-wire voltage *drop*, of course) needs to be higher if the current is lower.

      So, high operating voltages reduce distribution losses.

      The same analysis works for AC too, and is the reason that trans-continental transmission wires have such crazy-high voltages. AC has additional losses due to radiation and induction, of course.

    • by hpa (7948)
      380 V is presumably because it is the phase-to-phase voltage in 220 V 3-phase wiring, so there is plenty of distribution products already rated for that voltage. Why 380 V and not 400 V (230 V 3-phase, which is the modern standard) is a good question; it might have been what they actually intended.
  • The article says that 380v DC is the sweet spot, but why? Here in the US 440v (3 phase) AC is pretty common, as is 220v AC. I realize there's a world of difference between AC and DC, but that's about all I can think of. 380/4=95 x 4v rails I suppose? Someone with an EE degree or master electrician jump in here and explain this to me please.

    • Re:Why 380v? (Score:5, Informative)

      by RichMan (8097) on Wednesday November 30, 2011 @05:02PM (#38219664)

      440 * sin(120) = 381.05 ....

      3 phase has 2 ways of looking at the voltages, Y or delta.
      The 3 phase delta is 440v when you measure between any pair of the 3 wires. The center point is ground. You don't see that in delta, but you do when measuring it in Y form. The same signals that are 440v when measured as a pair are 3 x 380v when looked at in the Y configuration.

      So 3 phase 440v gives you 3x 380v to ground.

      As to the 12v/5v/1.5v/ whatever you are going to have to do DC to DC all over the place. Better to have as high a voltage as possible for less current and less losses.

    • by Mr Z (6791)
      Well, it would allow for about a 10% sag in the AC source, if that was 440v. 90% of 440v is 396v, which gives you some margin for conversion losses.
    • by russotto (537200)

      The article says that 380v DC is the sweet spot, but why? Here in the US 440v (3 phase) AC is pretty common, as is 220v AC. I realize there's a world of difference between AC and DC, but that's about all I can think of.

      They've probably figured that common power supplies designed for 240VAC can be run off 380VDC by bypassing the rectifier diodes. Doing the math gets you 340V, but maybe they've looked at the actual devices available or in common use.

    • by vlm (69642)

      The article says that 380v DC is the sweet spot, but why? Here in the US 440v (3 phase) AC is pretty common, as is 220v AC. I realize there's a world of difference between AC and DC, but that's about all I can think of. 380/4=95 x 4v rails I suppose? Someone with an EE degree or master electrician jump in here and explain this to me please.

      OK

      Look at the input stage of a stereotypical switchmode power supply. in 120 volt mode you see a voltage doubler config. In 220 volt config you see a plain ole straight rectifier. (If you ever wondered why you can run a switcher configured for 220 on 120 with no fireworks, but config for 120 and plug into 220 and it blows up, now you know) Your DC voltage to the input of the switch mode chopper is gonna hover right around......... 380 volts. No point getting overly precise because line voltage and comp

  • by mlts (1038732) * on Wednesday November 30, 2011 @04:58PM (#38219588)

    If one has worked in a telco, we already have a standard, and that is 48VDC. This is the domain of the Sun Netras of yore.

    If I were to recommend a voltage, why not plain old 12VDC? Yes, the amps have to be high, but we already have a connector for this (beats wiring up things by hand and throwing a breaker), and it is not hard to find off the shelf hardware to support this, be it batteries, power distribution units, inverters/converters, solar panels with MPPT controllers, and so on. We have two large markets (RV/marine) that are dedicated to 12VDC.

    Why not just use an established standard? 12VDC works and has a lot of support, or if a higher voltage is needed, then 48VDC.

    384VDC just seems to be asking for trouble. It would require yet another separate connector that can't be plugged into 120VAC or 240VAC, generators would have to have an adapter for it. It would require a complete retooling to get to that standard.

    Making another voltage level is throwing the baby out with the bathwater. Why not just go with an established DC voltage level?

    Take 12VDC. Most generators, from the expensive inverters by Honda or Yamaha can generate that, as well as the construction grade open-framed ones.

    • why not plain old 12VDC?

      Look up the rating of the power supply currently operating your computer then calculate how many amps would be required to deliver that power at 12 volts. Look up the gauge of wire that would be required to supply that much current without melting the insulation. Then multiply by the number of computers in a typical data center.

    • by geekmux (1040042)

      384VDC just seems to be asking for trouble. It would require yet another separate connector that can't be plugged into 120VAC or 240VAC, generators would have to have an adapter for it. It would require a complete retooling to get to that standard....

      I'm sorry, but according to the 1%, you've exceeded the allowed threshold for Common Sense with your remarks here. Such atrocities against Greed will not be allowed or tolerated.

      Anytime a new standard is being proposed, you can bet there are several people standing behind it poised to make money off it. And based on your suggested necessary changes, they stand to make a lot of money off this new standard.

      Who ever said the creation of new standards needed to make sense anymore? We're here to feed the 1% a

    • by mkiwi (585287)

      384 VDC is a common voltage used in "Boost" regulators that are universal input. That's probably why that voltage was used. You obviously can't power a microprocessor off of a 384V line (SiC would be necessary to withstand the high voltage). There has to be some sort of switching going on.

      I have not RTFA, but what would make sense to me would be to use a boost converter to get 384V, send that 384V all around the building, then convert it down to 12V, 5V, 3.3V, and 1.2V using a few large DC-DC converters.

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