40KW FSW Inverter

[(unknown)]

Brand new user here. I have been searching for several years for an inexpensive

sine wave inverter with 120V, 60 Hz out and input of around 120 to 170 VDC. Today i happened on a 2004 article here from 'Ibedonc', entitled: "My adventures with designing a full sine wave PWM inverter". I read every attachment. It dosent seem to have an ending.  Are you still around Ibedonc?  I am very interested to learn the rest of the story.  I would gladly pay $ to learn the results and obtain schematics.

Also, someone suggested the idea of taking an off the shelf 12 or 24 VDC input sine wave inverter and simply bypassing the front end by connecting a 120 (or so) DC input directly to the filter cap where the front end's step-up output would normally feed the output switch.  I actually came up with that idea myself several years ago, but have not tried it because i assume it would be necessary to partially disable some of the low voltage dc input in order to prevent any conflicts which might result in smoke, but still enabling the overally unit to function. So far i have never seen any sine wave inverter with a schematic available.  They seem to be gaurded jealously.  I eagerly look forward to postings from anyone with knowledge in these areas.  Sincerely; MichaelB

[whatsnext]

I think Ibendonc and a couple of others here got a little tired of having to do the work while everyone else just chanted "more, more" while demanding schematics that probably had some commercial value. I don't think there ever was an "ending to the story" as I understand Ibendonc had other pressing issues to take care of first before he did free design work for us.  I remember some issues also about people who really shouldn't even have a soldering gun in their hands asking for group buys of parts and PCBs and some of the real designers here started to worry about them frying themselves.

John...

[Nando]

Michael:

An Inverter for 120 Vdc capable of a sine wave output requires voltage conversion to produce 200 Vdc positive and 200 Vdc negative for 115 Vac.

One can make it with a single 200 Vdc, but is more complicated and have a few more issues.

To produce a sine wave a PWM signal is needed to feed a Choke or Inductance and such process requires voltages higher than the peak voltage than the peak voltage of the sine wave.

Also, your message heading say 40 KW is that right ?.

A MSW using 120 volts is easier and capable of several KWs.

You said:

"'Ibedonc', entitled: "My adventures with designing a full sine wave PWM inverter". "

It may be still an adventure for IBEDONC ---.

Nando

[(unknown)]

Yes. Re; the 40KW header, was the power that Ibedonc had referred to as the amount his unit was already capable of in 2004. (The series of 24 postings on this unit is on this website).  We have over 40 1000 amp 12v cells available to configure any way we choose to feed an inverter. For various reasons, it is preferred to use higher input voltage rather than paralled 12v batts.  

[Nando]

40 batteries 12 Volts each = 480 volts

Here you have the voltage and power to generate 40 KW, -- by the way, I think that it was 4.0 KW and not 40 .

I have done design of high power UPS which is what you are mentioning.

It would be a major project for any one to "tackle" such magnitude of work.

A 40 KW project may take 2 to 4000 hours of work for several people to finish such effort.

I am advocate for high voltage, which you did not care to present the reasons for high voltage converter.

Assuming that you have a high voltage AC inverter, how do you plan to charge the batteries.

Nando

[(unknown)]

40kw is great, but i really dont need that much.  Again, i only mentioned it because that is the amount stated by the original author: Ibedonc. In fact, he claimed to have achieved 40KW as a minimal amount, and he went on to say it could easilly be increased to well over 100 KW. Again, this is all to be found on this web site in the original 2004 set of 24 postings entitled "My adventures with designing a full sine power inverter". He claimed to have taken this from concept to working model in only about 2-3 months i think.   Remember, his concept (which i really like) is to start by providing the correct DC input such that its switched sine output results in 120 VAC.  Even with my basic understanding it would seem that by eliminating all circuits required to achieve the dc/dc converter, you are left only requiring a switch to go from DC to AC.  Seemingly, this could eliminate at least 1/2 of the required complexity?

Anyway, for my purposes, 3-5 KW would be great for now.  What do you think of the idea of taking a 12V off the shelf sine wave inverter and simply externally injecting the required high DC voltage directly to the power supply filter cap?

It seems a little to simple to me. I think the primary dc/dc converter would have to be disable first, but withou disconnecting the low voltage required to operate the output switch. Maybe difficult without a schematic of unit being modified.

-MichaelB

[nothing to lose]

I think 120Vdc is kinda dangerous to work with, far more so than 120Vac.

Well not that I would want to try such things myself, but if you want to give it a go may I suggest taking a cheap used working UPS and try modifing that. Cheap to play with, no great loss if the magic smoke escapes. Long as you don't hurt yourself.

Depending on country, A UPS runs on 120Vac while the grid is on, switches to batteries and inverter when grid goes off, charges batteries when grid comes back on. All your parts are there.

You don't need the grid or the charging parts, just the inverter parts. I bought 1000watt sinewave UPS's for $5 each awhile back, just needed new batteries. They appeared to be junk, not even turn on with grid power. Connected good 24V battery bank and they work perfect. Even startup with battery power only so no grid needed for anything.

Bought a Rack Mount 1750watt sinewave UPS for $20 which also works perfect.

 I don't care to try such things myself, but if you are capable of attemping such work I think UPS's would be a good cheap base for experementing. Fry a $5 or $20 ups and your out of a good piece of hardware but not much money. Fry a $200 or $2000 inverter your out lots of money and the hardware.

If you can get the UPS to run off your 120Vdc or higher then you could try regular inverters if you need to for some reason. Might be the UPS itself would be better than a stock inverter once you remove the DC/DC boosting circuit, maybe add some larger heat sinks also.

If your carefull playing inside a live device like that, you might be able to measure the volts at various points to determine where to connect the battery bank and exactly how many volts DC is needed.

No matter what kind of inverter, how will you trigger a low battery warning or shutdown for such high DC volts, or are you going to skip such things?

I don't suggest doing such things, only a cheap source for test systems.

Many members here could probably rebuild fried inverters if they wanted too, others like myself are lucky to figure out how to turn them on. Well, not that bad maybe.

 If you don't know what your doing, don't do it! Only you know your own skills and abilities, don't exceeded them and hurt yourself.

I don't even like playing with over 100Vdc for running motors myself,  I do it, I just don't like too. Trying to run an inverter directly from such needed high DC volts is not something I plan to try anytime soon myself.

[(unknown)]

Dear Nothint to lose;

Great idea to experiment on a 1kw sine ups.  Any surrestions where i may be able to get a used one for a great bargain as you did? Thanks- MichaelB

[ghurd]

Cleveland!

[commanda]

eBay !!!!!

My 2 x 12 volt deep cycle batteries in my test/experimentation setup are currently sitting on float charge off a cheap ups I picked up on ebay with dead batteries.

Amanda

[nothing to lose]

Maybe local computer repair/sales shops? The correct batteries are expensive, many/most people just toss the old working UPS and buy a new one. Repair shops toss them often, sometimes e-bay them maybe.

If near a decent sized city, watch for auctions that may have such things. If an ISP goes under, they probably had one or more rack mounts maybe. Unless a dealer shows up, how many people really want such things? My favorite ISP went under awhile back, got hacked 2 twice, but they kept all the hardware.

Many types of businesses use various types of UPSs. Watch for places being sold out, going under. If a large grocery store goes under and the office equipment is being auctioned with store stock, there could be a great UPS in there. Watch for those type auctions, businesses that would demand the computers stay running for awhile durring a power outage.

Watch E-bay for used ones without batteries near you or someplace you want to go anyway and pick it up. Shipping can be high. The $560 Matrix 5000 I bought in Ohio would have cost me $300 for shipping. 800 mile drive, but I go near there anyway. So I drove up and got it free pickup. Same time on Ebay I found a 2200 rack mount UPS selling for $20 and $200 shipping, I bought it for $20 and free pickup, it was near the Matrix so no big deal.

 I got the $5 UPS's as non-working for parts when I picked up the 2200.

It was a nice drive up and turned into a mini vacation, I even got to visit with Ghurd on the trip.

The deals are there you got to watch for them and be flexable. I just bought another Matrix 5000 in Chicago for $180. A friend is picking that one up and storing it for me till I go visit soon, so again no shipping which may have been near $300.

Actaully for the first testings any UPS should give you an idea. Most "SMART" Ups's are  sinewave. But for experimenting even a modwave should be fine and more easy to find cheap or free since most average people probably have those wal-mart cheapies.

Since your looking for a way to bypass the DC/DC converter and drive the inverter from direct high DC volts any working UPS you find cheap or free should be good for testing, even a 200watt modwave if found free. Once you figure out the small ones I am geussing the larger ones will be about the same plus you will be less likely to fry the bigger ones knowing more about the little ones already.

Oh, and if I were doing this and made a mistake, I think I would rather be Zapped by 120Vac at 200watts than 120Vac at 3,000 watts. Probably an optional illusion but it just seems like 200watts would be less serious, though either could kill you I'm pretty sure.

I don't plan to do this myself. Agian, if you don't know much about what your doing then don't do it. Large ZAPS may not be fun, they could kill you or ruin your life.

 I had a friend I don't see often these days. He was in electronics repair and great health. Then one day I went to visit and he has the shakes super bad. He did not say, I did not ask, but I am pretty sure he took a high voltage hit. Probably fried nerves or something.

 How he feeds himself I don't know, with his shakes it would be like trying to eat on a roller coaster. We are still friends of course, reason I seldom see him now is he can't drive anymore so he never comes here now. Needless to say he no longer rides a motorcycle or does electronic repairs either. Great guy only about 40 years old. Probably touched the wrong thing at the wrong time

[(unknown)]

What me worry? - MichaelB

[robl]

I ran off a 120VDC battery bank for about 14 years. Used rotary converters and PWM sine-wave inverters from Exeltech. I switched to 48VDC because I could not afford to upgrade my PV array in 120VDC segments.  

120VDC-in inverters use high internal dc voltages, they do not step down to lower voltages. The idea of using non-commercial UPS circuitry is likely a non-starter as their internal DC busses are rarely over 24VDC. Even the big rack mount enterprise-level units tend to stick with 48VDC.

I had a Toshiba 5KW 120VDC UPS unit for a while, and just the front-end iso transformer weighed a 100 pounds. The 1.1Kw Exeltech weighed less than 15 pounds.

Cheers

Rob