EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: mikeselectricstuff on July 22, 2014, 10:34:34 pm
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https://www.littleboxchallenge.com/ (https://www.littleboxchallenge.com/)
I kinda think they're trying to solve the wrong problem though.
Why spend all that effort converting HVDC to AC, only for a large proportion of appliances just rectify it back to HVDC again.
I wonder if they'd have been better off looking at ways to make appliances work safely & efficiently form variable HVDC supplies
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that's thinking outside the box. (sorry)
Totally agree, we can convert DC voltages very efficiently now so why not use it for most low-medium power appliances and especially lighting.
I guess you still need a grid tied inverter/rectifier though. That wont change soon.
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I also think they might be solving the wrong problem, by concentrating on size, instead of on efficiency and cost. Granted, if you make it small, you may have to make it reasonably efficient, because any waste energy has to be dumped as heat, and small boxes have trouble getting rid of heat without causing damage. But size is much less closely correlated with cost. I think the world needs cheap and efficient inverters more than it needs tiny ones.
I can agree with mikeselectricstuff's logic, as well. It's probably better to figure out how to avoid multiple conversion steps entirely, instead of figuring out how to do the conversions better.
On the other hand, if they do prompt people to solve the problem as they've stated it, even though it's not exactly the problem I would have proposed, it still may stretch the state of the art, and that's not such a bad thing.
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General purpose, I suppose...?
Maybe Elon Musk dropped by Google and said, "Ya know boys, your self driving cars are great, but my customers are going to need to run their coffee maker, while they're on the road charging their iPads. Wouldn't it be nice if there were a compact solution for that?"
The ripple requirement is ridiculous. Presumably they're thinking of electric car batteries or something like that, which will have much less than 10 ohms ESR, and won't care about ripple. (..Do they?)
They're also asking for a 30C temp rise ("15-30C ambient", 60C max at any point on the outer surface), which in under 40 in^3 x 0.5" = under 160 in^2 (two sided) and at typical convection rates of 150 C.in^2/W, that's about 30W tops. The minimum efficiency is 95%, so 100W max dissipation, and that's if you're willing to sacrifice internal volume for heatsinks and fans.
I'll have to run some numbers and see how far from theoretical the volume is.
Tim
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Totally agree, we can convert DC voltages very efficiently now so why not use it for most low-medium power appliances and especially lighting.
Don't most of the techniques used to convert DC-to-DC efficiently rely on an intermediate stage of AC? (Pulsed DC at least...) Transformers and inductors are used for just about everything but linear regulation. If AC is necessary anyway, why not stick to the tried and true? (Although sine waves are maybe an unnecessary burden a lot of the time.)
Now, I do see the benefit of relatively low-voltage DC buses in-home. I have considered setting up a large UPS-like system for stuff you really want working through (possibly extended) outages. E.g., lights, smoke detectors, alarm systems, boiler-room water pumps... We had a wind storm here a year ago that knocked out power to some neighborhoods for upwards of a week before the utilities could catch up. It was during the fall. A couple weeks later, and things would've gotten really bad -- pipes freezing, pets dying, etc. Assuming residents themselves could just go somewhere habitable, that is.
Anyway, I wonder how successful this is going to be. It seems efficiency is already getting pretty good. A few more percent would certainly be nice, but what's wrong with a cooler-sized device? Is that really a limiting factor for homes? (For vehicles, sure, I get it -- but then, do we need the inverter at all? Or is the DC rail voltage good enough as-is?) Curiouser and curiouser.
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Not sure I see the point in this. I've got 4500 watts of PV, a 436 AH 48V battery bank and a 3600 watt inverter for back up power of our modern 3000 square foot home. The inverter is not "cooler sized" (more like the size of a 12 pack of beer) - and it's size is really not an issue. Direct grid tie solar system inverters are even smaller.
BTW - DC only systems for off grid or back up lighting and appliances have been used for years. Modern inverters are so efficient that there is little to be gained. In addition, the cost of the additional copper needed to minimize losses with DC wiring and the extra cost and hassle of using DC only appliances has made this less and less popular.
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about the only thing you need 60hz ac for is single phase induction motors and florescent lighting. and cheap wall warts.
i'm not aware of a problem that needs fixing here.
off grid folks have always been left with three options: cheap msw inverters, cheap sine wave inverters, and expensive sine wave inverters.
expensive sine wave inverters don't blow up when you start a 5 hp induction motor, or accidentally short the output. some of the 6 kw sized units will have no problem running stick welders, which are about 50% lagging power factor.. worse if its SCR controlled. Typical "ratings" for a good quality inverter is something like double the rated output for 5 minutes.
usually the topology of sine wave inverters are up to dozens of phases of forward or flyback converters to take the 12,24,36,48 volts nominal battery voltage and convert it to a floating 300+vdc or +/- 180+vdc, then sent to a full wave or half wave bridge, then filter the output.
the input side forward or flyback converters can be turned off to save switching losses at low power, but the output side half or full bridge cannot.. unless they have multiphase output inverters.. which they might start doing.
it might be interesting to see if a three level inverter could be built from 200 volt mosfets and diodes with lower losses than a 2 level inverter from 600 volt rated IGBTs or 500 volt mosfets. to see such would be about the only thing i would find interesting resulting from this competition.
input ripple tolerances are rather interesting.. it looks like you could be forced to use a PFC boost converter to take the 450 volts and boost it to 550 in order to have sufficient energy storage in 600 volt electrolytics to keep the input ripple down.. that way you could let the voltage flop around from 550 volts to 450 volts on your energy storage caps to keep the input ripple down. --such a design would seriously eat into the minimum efficiency specification because its hard to get beyond 98% when dealing with boost converters, diodes and 650 volt mosfets. unless of course you triple the cost with resonant turn on and turn off circuitry.
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Greeting EEVBees:
--$1,000,000!!!! Just now in the register, a Household Inverter Design Contest.
--I was thinking that Dave could probably easily design one of these, perhaps by kickstarting the R&D budget. If only he knew some group that might be interested in his project.
http://www.theregister.co.uk/2014/07/22/google_offers_one_milleeon_dollars_to_inverting_acdc_boffins/ (http://www.theregister.co.uk/2014/07/22/google_offers_one_milleeon_dollars_to_inverting_acdc_boffins/)
"If Mr. Einstein doesn't like the natural laws of the universe, let him go back to where he came from."
Robert Benchley 1889 - 1945
Best Regards
Clear Ether
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https://www.google.com/search?q=upside+down+house&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=BTbPU9zTKoaOyATRoIHYAw&ved=0CBwQsAQ&biw=1920&bih=955 (https://www.google.com/search?q=upside+down+house&espv=2&tbm=isch&tbo=u&source=univ&sa=X&ei=BTbPU9zTKoaOyATRoIHYAw&ved=0CBwQsAQ&biw=1920&bih=955)
Do I win?
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The switching power supplies commonly found in consumer and computer gear will often work without problems with DC inputs from 170 to 340 volts.
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They just want somebody else to do their design for them. If I was going to go through the trouble to design it, I would sell the damn thing myself! The part 15 FCC bit will be the hard part. Handling that much power in 40 cubic inches starting from such a high voltage is easy enough. Meeting the noise requirements would be the tough part. I should make a big 10 square inch hydrogen thyratron, or better yet a mercury pool ignitron and a chopper circuit. Watch it blow up all their test gear when they go to try it out! Or a micro tesla coil and have it send arcs all over their lab!
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mercury pool ignitron and a chopper circuit. Watch it blow up all their test gear when they go to try it out!
how many volts per nanosecond do i need?
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I am not sure household HVDC distribution actually saves you that much. HVDC-DC power supplies don't really have any advantage over AC-DC. DC-AC inverters are more troublesome, but I don't think that is fundamental: they are just much less common and haven't been optimized greatly. The obvious benefit of AC is the ability to use induction motors and magnetic fluorescent ballasts, which is great, but those can be replaced with BLDC motor controllers and electronic ballasts. However, AC has superior arc clearing and switch rating/contact life. Between those advantages and market inertia, I don't see HVDC replacing AC any time soon.
A key point is that you don't actually get rid of inverters by going to HVDC distribution, you just replace them with DC-DC converters. Your solar panel or battery or whatever is likely to not put out the standard household voltage you decide on. In the case of solar panels you want to be doing power point tracking if possible, while some battery chemistries change substantially with state of charge. So you still need a converter.
Now DC for grid distribution is great. Right now it is mostly only used for long distance links or when connecting multiple grids, but I wouldn't be surprised if eventually we have DC distribution all the way to the neighborhood distribution point where the power company had an inverter that supplied people with household AC.
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HVDC in the household instead of AC ? back to Edison ? :D
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Would corrosion also be more of a problem with DC?
Such as with wiring joins subject to moisture.
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Would corrosion also be more of a problem with DC?
Such as with wiring joins subject to moisture.
I do not think it would be any worse than AC. Either will cause electrolysis. The power level is high so "high open" type failures like you find with telephone wiring are not going to happen.
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i think changing to DC would be a big pain in the ass for the end customer - how would the generic user know whether or not his device is suitable for DC ? for new products it's easy - the manufacturer could indicate on the product that it's suitable for both AC and DC input... but what about the billions of devices already manufactured ? even if the older equipment is suitable for DC - it's not indicated on the device.
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Why spend all that effort converting HVDC to AC, only for a large proportion of appliances just rectify it back to HVDC again.
Because almost everything on the plant needs that AC. Unless you plan on throwing everything away and starting again.
There is a need for both solutions.
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I do not think it would be any worse than AC. Either will cause electrolysis. The power level is high so "high open" type failures like you find with telephone wiring are not going to happen.
Balanced AC pushes those ions back on the next half cycle - no effective corrosion (unless you manage to engineer some weird copper-oxide semiconductor).
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first prototype drawing, they are working on making it a bit smaller.
(http://2.bp.blogspot.com/-1VEYoxIG894/T7tDwEKzKpI/AAAAAAAAGWo/RMSYJZPImnA/s320/Drawing+of+a+working+model+of+flux+capacitor.jpg)
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They are asking for power density, which is about 10 times the currently available inverters. I'm sure that the challange is possible, maybe it would be worth to make an asic for the control. But.
It wouldnt be cheap, it wouldnt be ready in time, and most likely it would be loud as hell. You still need to dissipate a lot of power and that needs cooling.
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I do not think it would be any worse than AC. Either will cause electrolysis. The power level is high so "high open" type failures like you find with telephone wiring are not going to happen.
Balanced AC pushes those ions back on the next half cycle - no effective corrosion (unless you manage to engineer some weird copper-oxide semiconductor).
I have run across electrolytic corrosion caused by wet conditions in power line AC wiring before. It may take a longer but the result is the same; it makes a big mess.
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i think changing to DC would be a big pain in the ass for the end customer - how would the generic user know whether or not his device is suitable for DC ? for new products it's easy - the manufacturer could indicate on the product that it's suitable for both AC and DC input... but what about the billions of devices already manufactured ? even if the older equipment is suitable for DC - it's not indicated on the device.
The only way this could safely work is with a deliberately incompatible power plug and socket as well as IEC connector. This might be a good idea anyway because of the non-extinguishing arc characteristics of high power DC.
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From the contest site:
One promising set of new technologies which may allow for the achievement of higher power densities are wide bandgap (WBG) semiconductors, such as Gallium Nitride (GaN) and Silicon Carbide (SiC).
Maybe they think we might be able use these to get higher switching rates. I can't see how else these semi conductors would help power densities.
If you could achieve a switching rate of 10x does anyone have a rough calc on what power densities you could then achieve?
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Maybe they think we might be able use these to get higher switching rates. I can't see how else these semi conductors would help power densities.
Possibly smaller heat sinks if they can operate at higher temperatures.
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Maybe less switching.
Check out Don Lancaster's Magic Sinewave pages.
http://www.tinaja.com/magsn01.shtml (http://www.tinaja.com/magsn01.shtml)
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Maybe less switching.
Check out Don Lancaster's Magic Sinewave pages.
Danm! You've revealed my secret. ;)
That technique requires choosing from canned waveforms to do voltage regulation, so the output voltage moves in steps.
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Maybe less switching.
Check out Don Lancaster's Magic Sinewave pages.
Danm! You've revealed my secret. ;)
That technique requires choosing from canned waveforms to do voltage regulation, so the output voltage moves in steps.
Did you ever implement succesfully one of Dons algorithms?
I have been looking at it for years but still was not able to formulate the thing for a PIC.
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Maybe less switching.
Check out Don Lancaster's Magic Sinewave pages.
http://www.tinaja.com/magsn01.shtml (http://www.tinaja.com/magsn01.shtml)
In the rules it said something about having to have an output frequency of between 59.7 - 60.3 hz; so would that magic sine thing be no good in this case?
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Do the rules say how long it needs to operate?
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This document gives a lot of info.
https://www.littleboxchallenge.com/pdf/LBC-InverterRequirements.pdf (https://www.littleboxchallenge.com/pdf/LBC-InverterRequirements.pdf)
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The problem I see with household DC power distribution is switching: If you use more than about 24V, you'll get long arcs when switching off. All kinds of switches and relays must therefore contain arc breakers. With AC this is not neccessary as the arc goes out at the next zero cross. Look at the prices and sizes for DC relays and switches which are designed for these voltages and some amps. This also was one of the main reasons why the car industry stopped their plan to switch from 12V to 48V some years ago.
If you stick to 24V and less, you need thick wires and have considerable cable losses.
So there are technical reasons for AC beyond the installed basis.
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This document gives a lot of info.
https://www.littleboxchallenge.com/pdf/LBC-InverterRequirements.pdf (https://www.littleboxchallenge.com/pdf/LBC-InverterRequirements.pdf)
the smart way of outsourcing the engineering job ;) it will cost them 1meg , but they will get a lot's of ideas and probably even the product in return ;)
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I will eat my shoes if I see a dspPIC or some sort of "dspish" controller in the final winning project, would be a giant step for innovation.
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From the contest site:
One promising set of new technologies which may allow for the achievement of higher power densities are wide bandgap (WBG) semiconductors, such as Gallium Nitride (GaN) and Silicon Carbide (SiC).
Maybe they think we might be able use these to get higher switching rates. I can't see how else these semi conductors would help power densities.
If you could achieve a switching rate of 10x does anyone have a rough calc on what power densities you could then achieve?
Switching, conduction, and drive losses will be lower at a given frequency so power total power dissipation will be lower. The operation frequency may be selected to balance power dissipation between various elements.
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And the inverter would still need to turn DC into AC. IMHO a lot depends on the magnetics. I wouldn't be surprised if someone comes up with a very smart setup for the inductors which has been patented 30 years ago.
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And the inverter would still need to turn DC into AC. IMHO a lot depends on the magnetics. I wouldn't be surprised if someone comes up with a very smart setup for the inductors which has been patented 30 years ago.
If it was patented 30 years ago then it will have expired.
The two common tricks I have seen for high density and low loss magnetics are using copper tape instead of wire and enclosing traces printed onto the circuit board with a planar E core.
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Did you ever implement succesfully one of Dons algorithms?
I have been looking at it for years but still was not able to formulate the thing for a PIC.
No, I have not tried it yet. I have kept it in mind for years too.
In the rules it said something about having to have an output frequency of between 59.7 - 60.3 hz; so would that magic sine thing be no good in this case?
There is nothing that would preclude using it to produce that frequency.
And the inverter would still need to turn DC into AC. IMHO a lot depends on the magnetics. I wouldn't be surprised if someone comes up with a very smart setup for the inductors which has been patented 30 years ago.
I don't think you need any magnetics for the power path conversion. Unless you mean for EMI filtering.
Do the rules say how long it needs to operate?
Yes. 100 hours.
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I don't think you need any magnetics for the power path conversion.
Can't just throw a PWM modified sine wave at the load since it can be partly capacitive which is going to generate losses ... if you want to do it with only say a full bridge worth of MOSFETs you'll need magnetics.
I guess you could do it without magnetics with switched capacitors, but you'd need a much larger amount of switches (and a lot of capacitors as well).
PS. the ripple spec would be hard to meet with switched capacitors though ... not impossible, but is going to increase the amount of switches/capacitors even more.
PPS. it doesn't make much sense to have the ripple requirement in my opinion, coping with ripple belongs with the preceding galvanically isolated DC DC converter which will generally be necessary (I wouldn't want solar panels with mains voltage on their ground connections for instance).
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I don't think you need any magnetics for the power path conversion.
Can't just throw a PWM modified sine wave at the load since it can be partly capacitive which is going to generate losses ... if you want to do it with only say a full bridge worth of MOSFETs you'll need magnetics.
I guess you could do it without magnetics with switched capacitors, but you'd need a much larger amount of switches (and a lot of capacitors as well).
Yes, it will need an LC output filter, but that's to meet the EMI and THD requirements.
the smart way of outsourcing the engineering job ;) it will cost them 1meg , but they will get a lot's of ideas and probably even the product in return ;)
They don't get the design for the $1M.
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If your submitting it for evaluation they get the design.
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If your submitting it for evaluation they get the design.
They don't look in the box.
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It does say they can reproduce it, but I don't see any requirement to submit any manufacturing data. On the face of it it looks like Magic Sine concept is out since that is owned by Don and the entrant would not be able to grant a license to reproduce it.
12. INTELLECTUAL PROPERTY RIGHTS: As between Google and the Entrant, the Entrant retains
ownership of all intellectual and industrial property rights (including moral rights) in and to the Device. As a
condition of entry, Entrant grants Google, its subsidiaries, agents and partner companies, a perpetual,
irrevocable, worldwide, royaltyfree, and nonexclusive license to use, reproduce, adapt, modify, publish,
distribute, publicly perform, create a derivative work from, and publicly display the Device (1) for the
purposes of allowing Google and the Judges to evaluate and test the Device for purposes of the Contest, and
(2) in connection with advertising and promotion via communication to the public or other groups, including,
but not limited to, the right to make screenshots, animations and device clips available for promotional
purposes. As stated elsewhere in these Rules, the Sponsor reserves the right to make public any technical
approach document submitted to the competition.
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Most of the space in an inverter is for voltage step up. Take that part out and the inverter can be a lot smaller. I have seen a 1kW inverter just a little bigger than a deck of cards used in a hybrid bicycle.
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Most of the space in an inverter is for voltage step up. Take that part out and the inverter can be a lot smaller. I have seen a 1kW inverter just a little bigger than a deck of cards used in a hybrid bicycle.
It was a brushless DC motor controller? 3 phases and operates the motor at battery voltage. So if we have high voltage DC in houses now all old appliances that require AC needs one of those bricks between it and the plug. Might be a bit hassle to explain that to some people.... "ah but this has worked before, why doesn't it work anymore?"
A variable frequency drive for a motor should be able to operate with DC voltage. Some airconditioners already include that, to change the speed instead of crude on-off control.
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In the rules it said something about having to have an output frequency of between 59.7 - 60.3 hz; so would that magic sine thing be no good in this case?
240 +/12 V AC
60 +/0.3Hz
So they managed to make a specification, which isn't used anywhere in the world.
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220V at 60Hz?
South Korea, Philippines, Peru and a bunch of island states.
Not exactly "nowhere in the world", but a very peculiar choice never the less.
I was under impression that the big problem was the 12-48VDC to 320VDC step-up part, not the 320VDC to 220VAC part.
Why would they focus on the last part?
Or is it about making higher efficiency pure sine wave inverter?
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They are asking for power density, which is about 10 times the currently available inverters. I'm sure that the challange is possible, maybe it would be worth to make an asic for the control. But.
It wouldnt be cheap, it wouldnt be ready in time, and most likely it would be loud as hell. You still need to dissipate a lot of power and that needs cooling.
basically what I was thinking. the output quality specs are brutal for that density and size, but it looks like 450 VDC to 240VAC which is not really what I was initially thinking would be a 1M$ campaign.
then again, I'm not up to date on power electronics. maybe if you gave me like 5 years to throw everything at the wall to see what sticks.
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Could it be that Google simply needs better power inverters for their data centers? That this is not about bringing small inverters to the homeowner masses?
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220V at 60Hz?
South Korea, Philippines, Peru and a bunch of island states.
Not exactly "nowhere in the world", but a very peculiar choice never the less.
Also the US. US residential supplies are 240 VAC. It is a split phase configuration and normal outlets only use one phase to get 120 VAC, but the backup generators and PV inverters normally produce 240 V. High power outlets used for things like electric ovens, clothes dryers, and electric cars use one of the various 240 VAC outlets.
Industrial settings don't have split phase transformers they normally have 3 phase feeds. In that case, you normally get the 208 V phase-phase voltage on the same outlets used for residential 240V.
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They are jealous of Ebay and their Fuel Cell backup generators ;)
But the answer is obvious:
https://www.kickstarter.com/projects/315398504/perpetual-solar-flywheel-energy-storage-by-energie (https://www.kickstarter.com/projects/315398504/perpetual-solar-flywheel-energy-storage-by-energie)
They didn't get funded and it's dangerous as heck, but flywheels will make a great inverter as far as energy conversion, just make sure the flywheel has no chance to break loose and create havoc in your home or business. One small enough to qualify if it broke loose it would be like a high energy cannon ball that will chew through everything in its path.
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In theory you could drive a flywheel with a "magic sine" and then run a generator off it (in essence you use the flywheel as a reactor, which is necessary with the "magic sine" approach to efficiently supply low PF loads). I doubt it's going to be as compact as a solid state device though.
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Could it be that Google simply needs better power inverters for their data centers? That this is not about bringing small inverters to the homeowner masses?
The only place you'd find an inverter in a datacenter (not counting VFDs in chillers or whatever) is in battery backup systems, and size definitely doesn't matter for those. But the cool thing these days for server farms is dual-supply servers that take unconditioned AC on one input (often at a higher voltage like 380V) and 48VDC from a battery bank on the other, and thus no inverter is used at all. Google and Facebook use this type of arrangement widely already.
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I thought they were using local backup batteries in their DCs? It has been a couple of years, so things may have changed, but I remember seeing commodity PC motherboards with a small SLA and a DC-to-DC converter all in the same chassis. You can lose power all the way to the unit PSU and it keeps running.
It seemed like about as efficient a setup as you could hope for. Power in -> transformer + rectifier or HVDC-to-LVDC -> battery -> DC-to-DC converter for required rail voltages. Easy.
Management-wise, it might be preferable to have it all centralized, but there are no shortage of solutions for battery bank to AC inversion, or native -48V power distribution. Right now, I'm sitting about two floors up from a big room full of lead-acid batteries. Certainly, the inverters aren't small, but compared to the space consumed by the battery bank, it's probably not on the short list of top problems to solve.
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The lead acid battery story is worth mentioning again because what they did was design their own motherboards that ran from 12 volts only, no 5 volt, and no 3.3 volt needed. (which really isn't that hard to do, and would reduce the cost of the power supply significantly)
then you can use a couple cheap mosfets to let the battery float at 13.xx volts while the motherboard runs from 12 volts.
when the power fails, the load pulls the battery voltage down to 12.56 volts fully charged which is well within operational tolerances.
why Goggle needs 450vdc to 240vac inverters i have no idea.
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I thought they were using local backup batteries in their DCs? It has been a couple of years, so things may have changed, but I remember seeing commodity PC motherboards with a small SLA and a DC-to-DC converter all in the same chassis. You can lose power all the way to the unit PSU and it keeps running.
I remember seeing the same motherboard design. There were or still are ATX power supplies available which include battery backup with an externally attached battery but I think they work by stepping the battery voltage up to 340 volts DC to power the existing switching power supply. A low voltage 12 volt implementation of the same thing is going to be more limited in output power.
Those ATX power supplies need an inverter to supply 120VAC to the monitor or other auxiliary equipment. One company (Amsdell?) had a tiny inverter which I think was SCR based and they made a big deal about how advanced it was.
Implementing the backup system directly on the motherboard makes sense because the high power point of load regulators already accept a 12 volt input and the individual motherboards and their attachments do not draw that much power anyway. 48 volts would be more efficient as a intermediate bus voltage but then the battery has 4 times as many cells and the point of load buck regulator has to run as 1/4 the duty cycle of the one which accepts a 12 volt input which may be a problem. Tapped inductors can be used to get around that issue but they would be another complication.
It seemed like about as efficient a setup as you could hope for. Power in -> transformer + rectifier or HVDC-to-LVDC -> battery -> DC-to-DC converter for required rail voltages. Easy.
Higher DC voltages are more efficient and needed for heavier loads anyway.
Management-wise, it might be preferable to have it all centralized, but there are no shortage of solutions for battery bank to AC inversion, or native -48V power distribution. Right now, I'm sitting about two floors up from a big room full of lead-acid batteries. Certainly, the inverters aren't small, but compared to the space consumed by the battery bank, it's probably not on the short list of top problems to solve.
Maybe it is for reliability? Centralized solutions tend to fail all at once and it makes interesting news when it happens at data center magnitudes. Watching the converter or transfer switch self destruct is probably something best viewed from a distance.
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why Goggle needs 450vdc to 240vac inverters i have no idea.
The HVDC power distribution includes an online UPS, i.e. a bunch of lead acid batteries in series. That's more efficient than using a battery bank with a large UPS (with inverters). But some stuff, like air conditioning, needs AC. Either you install a classic UPS for the AC powered stuff including the AC wiring or you use inverters directly powering the AC stuff.
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why Goggle needs 450vdc to 240vac inverters i have no idea.
The HVDC power distribution includes an online UPS, i.e. a bunch of lead acid batteries in series. That's more efficient than using a battery bank with a large UPS (with inverters). But some stuff, like air conditioning, needs AC. Either you install a classic UPS for the AC powered stuff including the AC wiring or you use inverters directly powering the AC stuff.
The funny part about that is that high efficiency air conditioners use variable speed drives so internally they rectify the AC to DC before chopping it up to drive the motor anyway. It is turtles all the way down.
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The funny part about that is that high efficiency air conditioners use variable speed drives so internally they rectify the AC to DC before chopping it up to drive the motor anyway. It is turtles all the way down.
There are also a lot of pumps involved. But I assume that more and more of the utility systems will be migrated to HVDC too.
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no, their custom server boards that i recall reading about ran the board directly from the lead acid battery in the case of a power outage, no reason to waste power converting it back to 340vdc to send it through the power supply.
but you need sealed cells to do that at the server level.
saturated cells running at 450 volts makes a lot more sense.
however, why bother converting the 450vdc back to 240vac, then back to 400 volts in a boost converter, then turn that into 200vac at 100Khz and back to 12vdc.
just go directly from 11kvac transformer to 480 vac to 450vdc through a 12 pulse transformer (no power factor correction required) (insert lead acid storage here)
then take that 450vdc and feed it right into the forward/flyback/LLC "ATX" power supply.
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That's kind of funny actually, because laptops generally run an internal 12-20V bus from which all the supplies run. I counted, I think: ~1.2V (core), 1.8V (mobile RAM, PCIe?), 2.5V (peripherals? / PCIe?), 3.3V and 5V (main logic, peripherals), and a battery controller -- six synchronous converters in all, in the last laptop I took apart. All of them have the same common bus coming in the top of the converters (easily proven, as it is easy to find the high side drain pins and their meaty ceramic bypass caps).
PCs are kind of silly, always having to maintain backwards compatibility. It would be very difficult to migrate suddenly, when few ATX+ supplies even tolerate asymmetrical loading of outputs. So, they haven't done this, gone all to just 12V or whatever.
Tim
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To minimise copper losses the next generation PC should have a 28~40V DC bus and a 5V standby only. No need to have -12V,3.3V&5V with associated minimum loads and regulation issues, also much lower copper losses.
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I never understood the 3.3v rail. Anything less than 5v really should be point-of-load regulated. This is clearly understood by the inclusion of the 3.3v sense return. They had the perfect opportunity to leave out another entire rail when they changed from the AT connector years back.
I also wonder how often (if ever) the 12v rail gets used directly. Some of those mini-ITX (etc.) PSUs take 12v in, and pass it right through with barely a bypass cap. No assumptions can be made about the quality of power coming in, so I assume (?) the designers of such PSUs either don't care at all, or count on the fact that nothing downstream is going to use that rail for anything but high-current buck converters anyway.
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18V or 24V would probably be the most optimal battery voltage if the load is right next to it. 12V has the disadvantage that the actual battery voltage could be either higher or lower than 12V, meaning a more complex DC/DC converter design.
I have seen a server that used a 20V PSU capable of supplying about 60A.
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Has anyone done some math on what kind of input capacitance you need to reach the input ripple?
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I never understood the 3.3v rail. Anything less than 5v really should be point-of-load regulated. This is clearly understood by the inclusion of the 3.3v sense return. They had the perfect opportunity to leave out another entire rail when they changed from the AT connector years back.
There was a fair amount of logic which could operate on 3.3 volts directly and currents were low enough that low dropout linear point of load regulators could be used to generate lower voltages from the 3.3 volt rail at with good efficiency.
I also wonder how often (if ever) the 12v rail gets used directly. Some of those mini-ITX (etc.) PSUs take 12v in, and pass it right through with barely a bypass cap. No assumptions can be made about the quality of power coming in, so I assume (?) the designers of such PSUs either don't care at all, or count on the fact that nothing downstream is going to use that rail for anything but high-current buck converters anyway.
12 volts is made available to expansion cards. Audio outputs and RS-232 can make use of it.
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18V or 24V would probably be the most optimal battery voltage if the load is right next to it. 12V has the disadvantage that the actual battery voltage could be either higher or lower than 12V, meaning a more complex DC/DC converter design.
Higher battery voltages will not help with input voltage variation and DC to DC converters are not going to care. Multiples of 12 volts has the advantage of cheap lead acid batteries.
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I never understood the 3.3v rail. Anything less than 5v really should be point-of-load regulated. This is clearly understood by the inclusion of the 3.3v sense return. They had the perfect opportunity to leave out another entire rail when they changed from the AT connector years back.
I believe the issue is that in the pentium pro era, practical switch mode regulators were not fast enough to supply the load transients demanded by the CPU. Therefore the point of load regulators were linear regulators and they wanted as low a voltage as practical to limit heat dissipation by the VRM. Of course, in the early 2000s switchers were getting better and core voltages were dropping rapidly to make linear regulators completely impractical, but that was well after ATX became standard. IIRC, the move to put everything on 12V started with the P4, which added the extra 12 V connector, but even then that was really only for the CPU. Everything else still ran off 5 and 3.3, which were the only high power connections available to PCI cards and at least the first generation of AGP. It wasn't really until PCIe that video cards started pulling a lot of power from 12V.
Now that all the high power stuff has moves to 12V, you could certainly get rid of the extra wires and put 3.3 and 5V DC DC converters on the motherboard, but other than saving a few pins on the power connector I am not sure what that saves you. It is basically free to hang an extra winding and diode on the main supply, and there are still a lot of things that need those voltages.
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Has anyone done some math on what kind of input capacitance you need to reach the input ripple?
oh, you mean the uh, rather insane specification of 20% ripple?
i suspect they want it that low so that they do not have to sychronize the sine wave outputs.
but yes, it is retarded.
three phase ac would demand 16% ripple with no input filter at all.
lol.
I suspect you will need to put a PFC boost or buck converter between the 450volts dc input and the full bridge ac inverter to win this competition.
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There was a fair amount of logic which could operate on 3.3 volts directly and currents were low enough that low dropout linear point of load regulators could be used to generate lower voltages from the 3.3 volt rail at with good efficiency.
12 volts is made available to expansion cards. Audio outputs and RS-232 can make use of it.
True -- however, is it common practice to use the rails from the PSU directly? (Honestly don't know.) E.g., if you were Asus, would you attach your 3.3v logic directly to the 3.3v rail from the PSU, or would you use a 5v-to-3.3v regulator? If that latter, is there any point in providing key voltages, or does it make more sense to offer something that is within comfortable drop-out range of target voltages?
As for 12v -- agreed, those are the most likely uses. But, it seems like most of the popular RS-232 interface ICs just use internal charge pumps now. Admittedly, that might be new since ATX's takeover two decades ago. (Which is probably why we still have a -12v rail that no one uses.)
For audio, most codecs now run from 5v or less. It might be useful for op-amps in higher-quality audio circuits, except no one worth their salt is going to use the output from a switchmode PSU without running it through a linear regulator first anyway.
It's kinda looking like you could get away with all kinds of crap on the 12v rail and nothing would care.
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OK, my 2c worth goes into a regenerative approach - a number of simple in-wheel alternators' fixed to and using the rotation of the axles to create a high amplitude, very irregular, alternating, phase incoherent waveform that is effectively free from the forward or reverse vehicle motion.
Rectify & smooth to charge (large) supercaps (batteries only needed to initiate acceleration from zero) - as the harsh AC is present to sustain the supply when needed. some smarts could be added to sense the phase relationships between wheels, and route non-synchronous waveforms around the wheels to provide 'free' electromagnetic braking.
All part of existing regenerative charging and braking - but taken to a ridiculous and potentially (no pun) meaningful extreme.
A small block of batteries to provide the first 0-10kmh acceleration, then asynchronous AC-> DC closed loop to sustain drive and braking. The batteries can also augment instantaneous shortfalls in the bumpy alternator waveform
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True -- however, is it common practice to use the rails from the PSU directly? (Honestly don't know.) E.g., if you were Asus, would you attach your 3.3v logic directly to the 3.3v rail from the PSU, or would you use a 5v-to-3.3v regulator? If that latter, is there any point in providing key voltages, or does it make more sense to offer something that is within comfortable drop-out range of target voltages?
Yes, 3.3 V logic on a motherboard would typically just directly off the ATX power, as would any 5V logic although I doubt there is any 5V logic or even IO left. The 5V USB supply and 3.3 and 5 V supplies to PCIe would also be taken directly from the ATX power (with a polyfuse or active current limit on the USB 5V). Any chips on expansion cards that needed those voltages would also just use them unless they needed a lot of current which would justify stepping down from the 12 V line.
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There was a fair amount of logic which could operate on 3.3 volts directly and currents were low enough that low dropout linear point of load regulators could be used to generate lower voltages from the 3.3 volt rail at with good efficiency.
12 volts is made available to expansion cards. Audio outputs and RS-232 can make use of it.
True -- however, is it common practice to use the rails from the PSU directly? (Honestly don't know.) E.g., if you were Asus, would you attach your 3.3v logic directly to the 3.3v rail from the PSU, or would you use a 5v-to-3.3v regulator? If that latter, is there any point in providing key voltages, or does it make more sense to offer something that is within comfortable drop-out range of target voltages?
They would use the 3.3 volt supply directly if possible. Otherwise there would be no point in having it. Later processors had lower core supply voltages and initially a low dropout linear regulator was used to provide them powered by the 3.3 volt supply. Efficiency is good dropping 3.3 volts to 2.5 volts. The PCI bus supports both 5.0 or 3.3 volt signaling.
As for 12v -- agreed, those are the most likely uses. But, it seems like most of the popular RS-232 interface ICs just use internal charge pumps now. Admittedly, that might be new since ATX's takeover two decades ago. (Which is probably why we still have a -12v rail that no one uses.)
The commonly used 1488 RS-232 line driver uses +/-12 volt supplies. Later level shifters included charge pumps.
For audio, most codecs now run from 5v or less. It might be useful for op-amps in higher-quality audio circuits, except no one worth their salt is going to use the output from a switchmode PSU without running it through a linear regulator first anyway.
Now they do but 12 volts is still useful for signal conditioning and if you have a power amplifier.
It's kinda looking like you could get away with all kinds of crap on the 12v rail and nothing would care.
That is the case even now.
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Has anyone done some math on what kind of input capacitance you need to reach the input ripple?
Don't know why they give different figures for voltage (20%) and current (3%), but clearly the 3% figure is the problem.
3% of 450V is 13.5V, and that's peak to peak over the low frequency content (excluding HF noise). An average 2kW load goes from 0-4kW during the cycle, and varies according to the sin^2 t = (1+sin(2*t))/2 identity. Therefore, the AC component of the current draw is sinusoidal, twice the frequency of the output, and peak-to-peak equals the (0-4kW) / (450V) spread, or 8.9A (it's actually a distorted sine, more current at lower voltages due to supply droop). Let's say it's 10A. Worst case frequency is 50Hz, or a ripple of 100Hz. The reactance must be less than 13.5Vpp / 10App = 1.35 ohms, or 1179uF.
Snap-ins would be good, a row of 10 x 100uF 450V parts would be... (consulting the Digikey oracle here) maybe a 22 x 32 mm can (http://www.digikey.com/product-detail/en/LGX2W101MELZ30/493-7986-ND/3929851), x 10 would fit along an 8.6" length side of a flat rectangular shape enclosure. So actually, that's not too terrible.
I don't think PFC is going to cut it: you're trying to squeeze a PFC switch, controller, inductor -- and don't forget the outside filtering and EMI components for it too! -- into the space of, say, 5-7 of those electrolytics.
Tim
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The 500v ones (lets have just a bit of safety margin) are 40 length, add in the snap ins and 2x1mm sheet metal we get to 46mm ... lets assume non staggered mounting, that's 22^2*46*10 = 222640 mm^3 ~= 13.59 inches. So a third of your volume gone on just the input capacitors (and your board area with a single PCB).
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More like 1/4 the volume with the cap I highlighted... or in other words, each one is about a cubic inch (square prism outline volume).
Challenge is to do a PFC in less. You still need electrolytics in there, period, no choice on that: absolutely nothing else offers the energy density and ripple current ratings required. A monstrous chain of supercaps, forget about it. Film, you're out of your mind. And if you use too few, you won't even have that, just huge plumes of magic smoke. I wouldn't think you could get away with less than three, so you need to pack that PFC (sans output filter cap) into less than 7 in^3. That's still a tall order.
And really, why would you go out of your way to choose bigger caps? It only has to run 100 hours, beat them up! ;D
Tim
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Challenge is to do a PFC in less. You still need electrolytics in there, period, no choice on that: absolutely nothing else offers the energy density and ripple current ratings required. A monstrous chain of supercaps, forget about it. Film, you're out of your mind. And if you use too few, you won't even have that, just huge plumes of magic smoke. I wouldn't think you could get away with less than three, so you need to pack that PFC (sans output filter cap) into less than 7 in^3. That's still a tall order.
Suppose you boost the 450 volts up to 550 volts.
you can let the dc voltage on that 550 volt rail vary from 550 to 450 volts.
yes, that's a hell of a ripple but you can get away with a lot less stored energy.
difficult part would be finding capacitors that can handle that ripple.
another alternative is bucking the input down from 450 volts to 350 volts. suppose you use 450 volt rated electrolytics, and you let the voltage on that rail swing from 350 to 450 volts.
same ripple, but larger capacitors needed. but you can use 450volt rated capacitors, instead of trying to find 550 volt or 600 volt caps.
also, the output mosfets can be 500 volt fets instead of the 600 volt fets required for the boost topology.
problem with buck is the input high frequency ripple. CCM boost makes more sense in that regard.
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Although they don't seem to have any constraints over input ripple, so you wouldn't need much bypass there. Maybe even do something shitty and RLC-quasi-resonant, using the 10 ohm source impedance to damp it.
Tim
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Only guessing here but wouldn't 95% efficiency be hard to achieve? Could you use a topology based on a class D amplifier with a MOSFET H bridge to produce a sine wave to increase efficiency?
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That's pretty much the idea, but when you're taking margins of single watts, every single thing counts. Example: a Qg = 100nC transistor takes about 1uJ to switch on and off; done 500,000 times per second over 4 transistors, that's 2W. Not much out of a 100W maximum budget, but every single component in the power or control path adds up quickly. You'll find 25 of those "nag" sources very easily. Add in the power transistors themselves (switching and conduction loss), filter chokes and so on, and you can blow the whole thing no problem.
If you aren't going for forced air cooling, your limit is even more critical, under 30W or thereabouts.
Tim
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Only guessing here but wouldn't 95% efficiency be hard to achieve? Could you use a topology based on a class D amplifier with a MOSFET H bridge to produce a sine wave to increase efficiency?
I can think of existing designs which are around 93% efficient which include an active power factor correction stage before the inverter so 95% does not seem unreasonable if cost is not a factor. They are much larger for the same power level though.
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So for such a small footprint I guess you would have to use heatpipes to help pull the heat to the top of the unit and to atmosphere. My laptop CPU+GPU draws around 100W full load and gets to 80 degrees at around 25 ambient so it would be possible to get that down a bit. For the size and the 60 degree limit, I would estimate a fan would be required. Otherwise a convection cooled setup using heat sinks integrated into the case design might just do it. The Sunny Boy 3000TL is 97% efficent and uses convenction cooling for a 3kVA unit, though the size is the limiting factor for that unit.
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So I guess you would have to use heatpipes to help pull the heat to the top of the unit and to atmosphere. My laptop CPU+GPU draws around 100W full load and gets to 80 degrees at around 25 ambient so it would be possible to get that down a bit.
That is what I would do. There is a major problem in this case because power is lost in very specific areas like the power transistors and it needs to be spread evenly over the whole surface of the enclosure to prevent hot spots because of the stated requirements. Heat pipes would be more effective then an equivalent thickness of aluminum.
The alternative would be forced air cooling which is not something you find in similarly high density switching power supplies because of poor reliability and operating life.
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There is a teardown of the sunnyboy model here - It even lists ICs used and shows the topology.
http://www.edn.com/design/power-management/4368876/Teardown-The-power-inverter--from-sunlight-to-power-grid (http://www.edn.com/design/power-management/4368876/Teardown-The-power-inverter--from-sunlight-to-power-grid)
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220V at 60Hz?
South Korea, Philippines, Peru and a bunch of island states.
Not exactly "nowhere in the world", but a very peculiar choice never the less.
Also the US. US residential supplies are 240 VAC. It is a split phase configuration and normal outlets only use one phase to get 120 VAC, but the backup generators and PV inverters normally produce 240 V. High power outlets used for things like electric ovens, clothes dryers, and electric cars use one of the various 240 VAC outlets.
Industrial settings don't have split phase transformers they normally have 3 phase feeds. In that case, you normally get the 208 V phase-phase voltage on the same outlets used for residential 240V.
220 is not 240. But yes, I always forget the weird 180 degrees 2 phase configuration of the USA. I was already surprised, that they didnt went for 110V as the "remote locations of the world", now I understand.
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Suppose you boost the 450 volts up to 550 volts.
you can let the dc voltage on that 550 volt rail vary from 550 to 450 volts.
yes, that's a hell of a ripple but you can get away with a lot less stored energy.
difficult part would be finding capacitors that can handle that ripple.
I assume you mean charge instead of energy?
Has anyone done some math on what kind of input capacitance you need to reach the input ripple?
Don't know why they give different figures for voltage (20%) and current (3%), but clearly the 3% figure is the problem.
Typo, It says 20% input current and 3% input voltage.
I cant see how the 20% figure comes into it either. Clearly 3% is the only problem because of the 10ohm source resistance.
I did a bit of a ball park to see how much energy needs to be stored during each half cycle to manage input ripple and provide energy for the half cycle.
8.33 joules. (very rubbery figure.)
If your pfc charged it's caps up to 400v and let them run down to 200v in the cycle. (Made these numbers up, we need to cope with 0.7 p.f. load.).
That would give 2x8.33(400^2-200^2) = 140uF.
Just on the input.
This is vastly different to T3sl4co1l's calculations, I guess it is the 8.33 Joules figure. But I am not sure how your calcs work T3sl4co1l. Not that I have explained mine.
3% of 450V is 13.5V, and that's peak to peak over the low frequency content (excluding HF noise). An average 2kW load goes from 0-4kW during the cycle, and varies according to the sin^2 t = (1+sin(2*t))/2 identity. Therefore, the AC component of the current draw is sinusoidal, twice the frequency of the output, and peak-to-peak equals the (0-4kW) / (450V) spread, or 8.9A (it's actually a distorted sine, more current at lower voltages due to supply droop). Let's say it's 10A. Worst case frequency is 50Hz, or a ripple of 100Hz. The reactance must be less than 13.5Vpp / 10App = 1.35 ohms, or 1179uF.
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220 is not 240.
Well, originally the US was more around 110/220 (with regional variations) and it is still quite common to call it that, even though the standard is now 120/240. It is also within (although near the bottom) of the +/- 10% commonly accepted band. 220 V is also relatively close to the industrial 208, so it is a good compromise voltage. No equipment designed to operate on either 208 or 240 VAC should have a problem with 220.
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Typo, It says 20% input current and 3% input voltage.
D'oh!
That would give 2x8.33(400^2-200^2) = 140uF.
Just on the input.
This is vastly different to T3sl4co1l's calculations, I guess it is the 8.33 Joules figure. But I am not sure how your calcs work T3sl4co1l. Not that I have explained mine.
Sounds reasonable, given the vast difference in ripple. You can calculate it either way, though only one method is easiest for each case. At low ripple, one can assume nice clean sine waves, and consider a single frequency in the AC steady state. For high ripple, the current will peak sharply (half voltage --> double the peak current draw and dV/dt -- it won't be a sine wave anymore), and an energy argument works much more nicely.
Interesting to note: your calculation uses 14 times more ripple voltage, but only 8.4 times less capacitance: this is correct, because capacitors store less energy at low voltages (indeed, going from 400V to 200V depletes 75% of the contained energy, and attempting to go lower wouldn't gain you very much), so by using a lower average voltage, you need relatively more (evidently, about double) capacitance.
Still, finding a cap that'll tolerate 50% ripple for over 100 hours, that fits in less than 10 in^3? That's a toughie.
Tim
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Thanks teslacoil, I was just wondering how my number was so different to yours.
I was envisioning a two stage converter-inverter with some storage caps in between.
This could give a steady current draw from the Source through a converter into the caps. This is to cope with the 3% input ripple.
This might be the equivalent of what somebody referred to as a PFC earlier.
Then you have the inverter to pump it out of these caps to the load at an instantaneous power of somewhere between 0 and 4 kWatts.
This will give me the 50% ripple on the caps. Roughly 400v down to 200v.
400 volts because on average you will never see more than 400 volts in due to the series resistance.
If only I had the expertise to make it.
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I think the world needs cheap and efficient inverters more than it needs tiny ones.
Many high volume manufactures needs tiny one, while they are very dificult to repair without sophisticated equipment and it will cost more than buying new, so they need small ones while BOM should be lower which means higher profits ;)
So, If you want something cheap and efficient DIY it and in the case of failure simply resolder failed element 8)
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A lot of the size and cost is in the passives ... tiny is cheap.
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So, If you want something cheap and efficient DIY it and in the case of failure simply resolder failed element 8)
Because we all know with high power electronics, one part just stops working and there are no consequences.
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I had a Panasonic sustain board blow one transistor. This then proceeded to take 16 others out with it plus their driver circuits.
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Instead of a heat pipe I was thinking along these lines. Assuming a H-bridge PWM topology, each leg consisting of two transistors and an inductor, use a whole bunch of those in parallel. The parts can then more easily be placed wherever you you would prefer to deal with the heat. The finer granularity makes it easier to find a place to fit everything. If the parallel transistors' on and off and off times are staggered slightly, it might help with meeting the radiated emissions requirement. Or switch a different set of transistors on each cycle (either the 60Hz or the modulation cycle) to more finely tune the heat distribution.
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Ya know, 600 of these things http://www.digikey.com/product-detail/en/C5750C0G2J104J280KC/445-13462-2-ND/3950698 (http://www.digikey.com/product-detail/en/C5750C0G2J104J280KC/445-13462-2-ND/3950698) stores 11.9J at rated voltage... in only 3.2 in^3... in an impossible assembly, of course.
Good luck with that, but an interesting observation nonetheless...
Tim
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I think some of you might be missing the point of the challenge: you don't get the $1M if you meet the specs, you only win if you are the smallest! Even if meeting the maximum size requirement of 40"sq isn't THAT hard, if someone makes one 39"sq they would win. You need to build it as small as you can and hope nobody builds one any smaller (smaller is baller). I don't want to go into too much details about the challenges associated with this project, where I think you should be looking, as I'm part of a small team of power electronics people taking a serious crack at this (none of us are in it for the money and we're a completely independent team, we are simply driven by building something cool - it's fun).
BTW it is the current requirement that is the 120Hz ripple figure you need to meet. At full power (5A, 400V) you're allowed 1A of ripple with 12V ripple. At lower power say 200W (0.448A, 445.5V) you're allowed 89.7mA ripple but a whopping 13.5V ripple. If you want to use bulk DC capacitance on the bus the worst case scenario is not 100% load, you actually need more DC capacitance to meet the current ripple requirements at lower loads given the 10ohm input impedence.
Some of the topology ideas here are interesting, but that's really only the first step of a long journey. Passives/filter requirements, switching frequency, transistor selection, gate drives, auxillary circuits, cooling, packaging, EMI/EMC, feedback controllers, software... the list goes on. And all the of these factors are related to each other - a huge multivariable problem, how do you optimise it?
It's not called a challenge because it's easy to meet the minimum specifications (I'm not saying it is). It's a challenge because it's hard to build the smallest unit that meets the specs.
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If anyone is still interested in this (I sure am), here is the approach taken by PES researcg group (Kolar et. al. a large/very good power electronics research group in Germany). Quite impressive, huge amount of work. (Note the use of not yet commercially available GaN devices...)
https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf (https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf)
Ya know, 600 of these things http://www.digikey.com/product-detail/en/C5750C0G2J104J280KC/445-13462-2-ND/3950698 (http://www.digikey.com/product-detail/en/C5750C0G2J104J280KC/445-13462-2-ND/3950698) stores 11.9J at rated voltage... in only 3.2 in^3... in an impossible assembly, of course.
Or 108 of these http://www.digikey.com.au/product-search/en?pv13=1529&k=ceralink&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25 (http://www.digikey.com.au/product-search/en?pv13=1529&k=ceralink&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25) in 3 in^3 (as the above team used).
Also, I'll throw up some photos of my teams unsucessful attempt (serious trouble with gate turn on due to miller capacitance and high dv/dt and no negative gate supply). My team was a team of 4, doing it independently in their free time (with lab support from where 2.5 of us work).
Did anyone else have a crack at it?
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So... They spent a million dollars building a $10000 dollar inverter with no practical use what-so-ever.
How is that better than the larger, but so-much-cheaper-you-can-actually-buy-it commodity inverters?
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So... They spent a million dollars building a $10000 dollar inverter with no practical use what-so-ever.
How is that better than the larger, but so-much-cheaper-you-can-actually-buy-it commodity inverters?
...and how exactly are the current "picnic cooler" sized inverters a big problem for household use? Even in a small mud hut you need things to sit on.
I guess you can't fit as many in a delivery truck as you could if they were 40 cubic inches, but... :-//
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If anyone is still interested in this (I sure am), here is the approach taken by PES researcg group (Kolar et. al. a large/very good power electronics research group in Germany). Quite impressive, huge amount of work. (Note the use of not yet commercially available GaN devices...)
That is quite impressive usage of the 3D envelope.
I have the feeling that this will be a lot easyer challange when the GaN FETs will reach maturity. With DrMOS like GaN power stages. Probably is would benefit if there would be an ASIc with analog control. And there should be a way to replace the inductors and capacitors wit a hybrid inductor-capacitor.
OK, I'm hibernating myself, wake me up in 20 years.
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i still don't understand why google wants a really expensive solution to solve the 120 hz ripple problem..
when you can simply make a three phase inverter.
:popcorn:
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https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf (https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf)
Do you have something like that from any other teams?
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i still don't understand why google wants a really expensive solution to solve the 120 hz ripple problem..
when you can simply make a three phase inverter.
:popcorn:
I'm surprised you didn't suggest 400Hz instead. Hey, it's a perfectly legitimate mains frequency... for some things...
(Suggesting 3ph of course just shifts it up to 360Hz. :) Albeit at more like 20% ripple, not 100%, so I'm not being quite fair with the joke.)
Tim
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https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf (https://www.pes.ee.ethz.ch/uploads/tx_ethpublications/Keynote_Presentation_ITELEC_15_FINALFINAL_as_published_251015.pdf)
Do you have something like that from any other teams?
I never put together a prototype unfortunately, but I enjoyed the analysis a bit:
http://seventransistorlabs.com/Images/Proposal_2014-07-26.pdf (http://seventransistorlabs.com/Images/Proposal_2014-07-26.pdf)
I didn't think it would be very much worthwhile to use different semiconductors (which were all but unavailable at the time -- and over a year later, are still hardly to be found!), the semiconductors being a vanishingly small part of the package (< 5%), even if you have to do crazy things with them to get the efficiency (multi level inverter perhaps?).
Naturally, I was having some trouble getting a simulation to show reasonable results. I tried a number of approaches, e.g.
http://seventransistorlabs.com/Images/Simulation_Screenshot1.png (http://seventransistorlabs.com/Images/Simulation_Screenshot1.png)
from which I discovered some glaring discrepancies in the models (it's rather hard to get 45 +/- 15W dissipation out of 2000W of power, when the effect of your models' errors is not like 1%, but 40%!). The general plan would've been ZVS with "too-small" filter inductors. Of course, this puts a large burden on the inductors, which need to be rather beefy, and extremely low loss.
ZVS is basically the only possibility for silicon. You need enough semiconductor to get conduction loss at least low enough to work (e.g., 70A transistors for a 7A load), and then you have to deal with the rather massive junction capacitance (which accounts for upwards of 100W, if it has to be charged dissipatively via hard switching or snubbers).
As for filtering, I find it interesting that the above review shows the ripple module taking up almost as much space as capacitors, anyway. Their capacitor multiplier (in effect) is rather sizable, more than doubling the volume of their capacitors alone. This is about what I expected. It might end up strictly smaller than using electrolytics, but the advantage for all that added effort is very, very slim.
I didn't know of those TDK ceramic link capacitors at the time, so I didn't have them tabulated. Anyway, it seems like C0G get better energy density anyway (and hell, about the same cost, considering they spent some $5k on capacitors in that damned thing!). But you still have to deal with it, which is a real stinker.
Another analytical oddity that may be of use: minimal volume filter designs. As filter order goes up, attenuation goes up, so the cutoff frequency can be closer to the attenuation limit (i.e., the frequency where attenuation must be e.g. 60dB). As order goes up, the number of components goes up (which means more energy storage), but as frequency goes up, the size of components goes down (which means less). I derived the formula assuming asymptotic behavior, which should be okay for modest filter designs (Butterworth to 1dB Chebyshev, say) and high attenuation (>40dB?). The ratio of cutoff to limit frequency, for this condition, is actually dependent on the desired attenuation only.
(Another aspect of minimum volume design would be relative component size. Inductors and capacitors don't carry the same energy densities. The ratio of L/C corresponds to filter impedance, so you will have the function of combined volume versus impedance, with a more or less parabolic curve, having a minima somewhere.)
Tim
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Another finalist.
http://www.iisb.fraunhofer.de/en/press_events/press_releases/pressearchiv/archiv_2015/Google_Little_Box_Challenge_2015.html (http://www.iisb.fraunhofer.de/en/press_events/press_releases/pressearchiv/archiv_2015/Google_Little_Box_Challenge_2015.html)
Not a lot of details, but DAMN that's small.
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I wonder if it meets the input ripple current requirement.
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http://googlegreenblog.blogspot.si/2015/10/finalists-announced-for-little-box.html (http://googlegreenblog.blogspot.si/2015/10/finalists-announced-for-little-box.html)
all of them
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3rd
http://blog.cet-power.com/2015/09/08/google-finalist-littleboxchallenge/ (http://blog.cet-power.com/2015/09/08/google-finalist-littleboxchallenge/)
https://www.flickr.com/photos/cet-power/sets/72157657889658778/ (https://www.flickr.com/photos/cet-power/sets/72157657889658778/)
4th
http://nadagy.pcriot.com/ (http://nadagy.pcriot.com/)
5th
http://www.smps.com/Design/Prometheus/Prometheus.shtml (http://www.smps.com/Design/Prometheus/Prometheus.shtml)
6th
http://www.cei.upm.es/blog/2015/09/25/google/ (http://www.cei.upm.es/blog/2015/09/25/google/)
7th
http://www.silicon-saxony.de/news/news-detail/archive/2015/september/article/little-box-challenge-die-olympiade-der-leistungselektroniker.html?tx_ttnews%5Bday%5D=10&cHash=4c5eb67c78ddbf567a4f0ad5efc4a1f4 (http://www.silicon-saxony.de/news/news-detail/archive/2015/september/article/little-box-challenge-die-olympiade-der-leistungselektroniker.html?tx_ttnews%5Bday%5D=10&cHash=4c5eb67c78ddbf567a4f0ad5efc4a1f4)
8th
http://www.aeri.unsw.edu.au/Google_inverter_competition (http://www.aeri.unsw.edu.au/Google_inverter_competition)
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The winners were announced some days ago:
https://www.littleboxchallenge.com/ (https://www.littleboxchallenge.com/)
http://googleresearch.blogspot.de/2016/02/and-winner-of-1-million-little-box.html (http://googleresearch.blogspot.de/2016/02/and-winner-of-1-million-little-box.html)
Looks like only three submissions survived the final test.
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I'am impressed . Winner has reached 145W/in3. I 've read their technical approach wich is interesting ! I think one of the most difficult part is the way to handle properly ZVS of the GaN !
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I wonder how close the finalists were to each other? There seems to be so much common ground between their approaches, it looks like it came down to the one with the slightly more polished solution.
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With the exponential growth of solar PV; more powerful and efficient inverters are required.
All that solar PV DC energy has to be tied to the AC power grid.
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How awesome is that? 3 times the density required.
I hope the team gets to keep the million. Though they probably did it on company time.
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WOW, talk about destroying the competition... electrical devils indeed...
(https://1.bp.blogspot.com/-_LrbTM5mjmE/VtS0PduuYDI/AAAAAAAAA7A/ovGYrmf8TOU/s640/correct_image.png)
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Fraunhofer got the highest power density, I think, with 12.27 W/cm³ (= 201 W/in³) and a space of just 10 in³. So basically four times the power density required... o_O
// it appears CET won because they had a higher power density, coupled with very good reliability in the 100 hour test.
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It seems that this chalenge is all about balance between power density and reliability ! I personally think that the winner team found the right one !
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A guy leading a team in the competition came in to speak to us at MIT the other day. Really interesting talk. They managed to get ~216W/cubic inch, but their inrush-limiting stuff failed in testing because Google changed the starting sequence from what they originally specified *apparently*.
Got to hold the thing and it was super impressive. Using a 7 stage flying capacitor inverter.