Interesting challenge. Probably beyond my skills to design myself. The input ripple requirements look like they may be the hard part to meet within the specified volume.What the inverter needs to do
The winning inverter will be the one that achieves the highest power density and meeting a list of other specifications, as determined by a panel of judges, while undergoing testing for 100 hours.
In brief, the other specifications are :
Must be able to handle up to 2 kVA loads
Must achieve a power density of equal to or greater than 50 W/in3
Must be able to handle loads with power factors from 0.7–1, leading and lagging in an islanded mode
Must be in a rectangular metal enclosure of no more than 40 in3
Will be taking in 450 V DC power in series with a 10 Ω resistor
Must output 240 V, 60 Hz AC single phase power
Must have a total harmonic distortion + noise on both voltage and current of < 5%
Must have an input ripple current of < 20%
Must have an input ripple voltage of < 3%
Must have a DC-AC efficiency of greater than 95%
Must maintain a temperature of no more than 60°C during operation everywhere on the outside of the device that can be touched.
Must conform to Electromagnetic Compliance standards as set out in FCC Part 15 B
Can not use any external source of cooling (e.g. water) other than air
Does not require galvanic isolation
Google little box challenge
Google little box challenge
https://www.littleboxchallenge.com/
The daylight is uncomfortably bright for eyes so long in the dark.
Re: Google little box challenge
A Cuk AC converter could do it and be bidirectional i.e. AC in DC out or DC in AC out. BTW that 10 ohm input resistance will cost you about 200 W. But otherwise the specs (except volume) are doable without much difficulty.hanelyp wrote:https://www.littleboxchallenge.com/Interesting challenge. Probably beyond my skills to design myself. The input ripple requirements look like they may be the hard part to meet within the specified volume.What the inverter needs to do
The winning inverter will be the one that achieves the highest power density and meeting a list of other specifications, as determined by a panel of judges, while undergoing testing for 100 hours.
In brief, the other specifications are :
Must be able to handle up to 2 kVA loads
Must achieve a power density of equal to or greater than 50 W/in3
Must be able to handle loads with power factors from 0.7–1, leading and lagging in an islanded mode
Must be in a rectangular metal enclosure of no more than 40 in3
Will be taking in 450 V DC power in series with a 10 Ω resistor
Must output 240 V, 60 Hz AC single phase power
Must have a total harmonic distortion + noise on both voltage and current of < 5%
Must have an input ripple current of < 20%
Must have an input ripple voltage of < 3%
Must have a DC-AC efficiency of greater than 95%
Must maintain a temperature of no more than 60°C during operation everywhere on the outside of the device that can be touched.
Must conform to Electromagnetic Compliance standards as set out in FCC Part 15 B
Can not use any external source of cooling (e.g. water) other than air
Does not require galvanic isolation
Engineering is the art of making what you want from what you can get at a profit.
Re: Google little box challenge
I disagree, the harmonic output limitations will likely impede the ability to stay within the stated device volume requirements and still meet power throughput and heat loading.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Re: Google little box challenge
Well I did note the volume problem. However, if the switching frequency is high enough the harmonic reqmts. should not be too difficult to meet. The biggest volume problem is the energy transfer capacitor if you go the Cuk route.ladajo wrote:I disagree, the harmonic output limitations will likely impede the ability to stay within the stated device volume requirements and still meet power throughput and heat loading.
Engineering is the art of making what you want from what you can get at a profit.
Re: Google little box challenge
Everything else doesn't look too bad if you ignore the input ripple, just draw power as needed and a low pass filter with a cutoff in the kHz range on output. With the input ripple constraints you need to store a fair amount of energy between peak and trough of the cycle.
The daylight is uncomfortably bright for eyes so long in the dark.
Re: Google little box challenge
Nope, disagree again. It will make it worse. Three phase invertors cause a huge amount of harmonic distortion and noise in the output, even using really sexy IGBTs or something better.However, if the switching frequency is high enough the harmonic reqmts. should not be too difficult to meet.
The output dampening is going to be a headache to be able to take the heat and fit in the can.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Re: Google little box challenge
Cuk converters can be designed for zero input and output ripple.hanelyp wrote:Everything else doesn't look too bad if you ignore the input ripple, just draw power as needed and a low pass filter with a cutoff in the kHz range on output. With the input ripple constraints you need to store a fair amount of energy between peak and trough of the cycle.
Engineering is the art of making what you want from what you can get at a profit.
Re: Google little box challenge
I take it you are not familiar with the Cuk converter. It has inductors on the input and output. If they are coupled inductors in a DC to DC converter the ripple can be made to be zero. AC does complicate that but the output inductor should help considerably. At worst you don't get current pulses. You get ramps.ladajo wrote:Nope, disagree again. It will make it worse. Three phase invertors cause a huge amount of harmonic distortion and noise in the output, even using really sexy IGBTs or something better.However, if the switching frequency is high enough the harmonic reqmts. should not be too difficult to meet.
The output dampening is going to be a headache to be able to take the heat and fit in the can.
Since there is no cost target I'd use SiC MOSFETs for voltage and current capabilities, speed, and very high temp operation reducing heat sink rqmts. I'd stay away from IGBTs due to the minority carrier current tail.
Engineering is the art of making what you want from what you can get at a profit.
Re: Google little box challenge
I take it you are not that familiar with variable frequency invertors.AC does complicate that but the output inductor should help considerably.
I do agree on looking for something cleaner than IGBTs. But as you said, it will cost.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
Re: Google little box challenge
I'm going from memory of the books Cuk put out (I think they were $150 for the set of 3) about 35 years ago. Since the memory is a tad hazy I didn't want to over promise. If I was actually going to do the project I'd do the proper research.ladajo wrote:I take it you are not that familiar with variable frequency invertors.AC does complicate that but the output inductor should help considerably.
I do agree on looking for something cleaner than IGBTs. But as you said, it will cost.
I have designed a DC-DC SEPIC with uncoupled inductors which is similar as to the capacitor energy transfer, but has a different topology on the output because it is non-inverting.
For AC Cuk used two converters in push-pull. And back then it was BJT stuff. I had assumed this project was single phase (but I just glanced at the spec). The 10 ohms on the input seems a real waster for the level of power indicated. .
Engineering is the art of making what you want from what you can get at a profit.
Re: Google little box challenge
The resistor in line with the DC source may be to protect the source from a malfunctioning inverter, or to simulate a source that naturally dips voltage under load like a battery.
The daylight is uncomfortably bright for eyes so long in the dark.
Re: Google little box challenge
I suspect it is the later.
What is interesting is they do not give much insight at all for application. Just the specs.
What is interesting is they do not give much insight at all for application. Just the specs.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)
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kunkmiester
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Re: Google little box challenge
I'd suspect they're looking for something for solar or wind applications. Not sure how the size requirements fit though.
Evil is evil, no matter how small
Re: Google little box challenge
Maybe a stupid question - but don't they say that it's an advantage in wilderness applications?
You can do anything you want with laws except make Americans obey them. | What I want to do is to look up S. . . . I call him the Schadenfreudean Man.