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Hi there, I would like to convert 220V DC to 220V AC 50hz true sine wave. What is the best solution?
Thank you in advance

DC motor driving an AC alternator.

Define Best?

Thanks Guys, Could you be a bit more specific?
I spent lots of hours today on the internet trying to learn more about it. I found so many different ones. 1 phase, or 3 phases? What DC level do I have to use? Lets say 12VDC or 220VDC?
or something else? Which type should I buy? How can I understand how they work? According to datasheets they are getting AC power and make DC motors works. I guess the trick is to use reversed, right?

I assume you want a true sine wave so you can sell power back to the power company. A switching supply is the most efficient, but getting a sine wave is difficult and expensive. The motor-alternator approach is simple but not very efficient. Whether you use single or 3 phase depends on how much power you are handling and whether 3 phase is available. The power company will put some limit on the amount of power you can generate single phase and put on the power grid. If you are using the power yourself, you don't have to be so concerned about the waveform.

Thank you Russ, yes I am thinking to sell power back to the grid. Naturally, the power company wants to see something working before discussing anything. A true sine wave oscillator would not be useful? I am not affraid to do a bit soldering if I could find a good design. My original idea was this. My solar panels our doing their best to recharge my 12V batteries. Here I can increase numbers. Than I would use the circuit that you saw to supply 30Amps. http://www.mitedu.freeserve.co.uk/Circu ... 230psu.htm Next would be a true sine wave oscillator from intersil, here I need to figure out the right frequescy, so it is pretty weak indead. ttp://www.intersil.com/products/deviceinfo.asp?pn=ICL8038 than increase output current by http://www.play-hookey.com/analog/incre ... rrent.html
and to finish with it http://home.golden.net/~kpwillia/mult.htm
Very possibly it would not work. That's why I am still searching for ideas. Also I need to find the right components. Most of all I am doing it all alone and I feel I need someone to check upon what I am doing.

Forgot to mention a current sense Amplifier from MAXIM http://www.maxim-ic.com/appnotes.cfm/ap ... 1934/ln/en
It is still just theory.

If you plan on selling power back to the grid you will need a way to syncronize the sine wave to that on the grid. The easiest way to do this is to use a motor/generator pair. Elevators use DC motors. To get the power to run these an AC motor drives a DC generator. In many cases the motor/generator share a common shaft and case. In in other words there is one physical device. Put AC in at one set of terminals, get DC out at another. The inside workings are several coils and a spinning armature. It may be possible to rewire one of these to do the reverse.<p>Another possible solution is to use an AC generator and DC motor. (Universal motors can take single phase AC or DC as their input and may be easier to come by than a large DC motor.)<p>It IS possible to do what you want and there could easily be an "off the shelf" solution. From my machines class for electrical engineering there was a way to syncronize a generator to the AC line then use either an electric motor, water (or steam) turbine, or internal combustion engine to supply power to the input shaft. Using a UPS or power inverter "circuit" solution might be more difficult than a mechanical one.

Thank you Jolly for your message. Could you pls advice on some models that I could study and compare costs, so I can understand a bit more. Lets say I need one AC generator and a DC motor. What size, and how much power do you think I could get out of them? The "off the shelf solution" would not permit me extending slowly and provide too little power for a relatively high initial cost. SunyBoy costs 3000USD and supplies only 2000W.

Selling power to the grid is really not that simple. I think that you should forget building this thing yourself, power companies are very critical about those who want to do this, with reason.<p>Unless you really know what you are doing I would steer away from it. It also doesn't make economical sense, you just can't make electricity at a lower cost from solar energy.<p>If you nevertheless want to do it (eg. for ecological reasons), go ahead but first inform yourself at the power company or the companies that provide the inverters and synchronizers. 3000 USD sounds a fair price for 2kW. Larger inverters will be cheaper per kilowatt.<p>good luck
Bert

Dear Bert, Thank you for your opinion. Unfortunately I cannot give you a technical answer and this is not a place for an emotional one. I have many other reasons not only ecological to go on with my project and I hope to help a lot of people in very difficult economical situation with it. Take care

instead of selling this electricity to the power grid, maybe you could use it for another porpose.The power companies will only give you what it cost them to prodouce it. You pay them that cost'+ aprofit.