108 to 120 voltage booster? 4kva

Discussion in 'The Projects Forum' started by maj113, Dec 7, 2014.

  1. maj113

    Thread Starter New Member

    May 26, 2012
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    hi all
    is there a way to raise 108vac output from a 'trace 4024k' full sine wave inverter? ok here is the story, i got this 4000va 'trace' inverter thru barter, to add to a 24vdc / solar / wind / rural utilities backup system, well, then the reason for such a good deal hits me. output voltage, 108vac. a call to the "trace" company informs me that this 4024k was not intended for use in these here united states. while it is 60 hertz, the 108vac is for some other country.....

    at sometime in my past i had heard talk of a "buck boost transformer". so when doing a brief cyberspace search, found this here AAC forum. an after reading some posts, i get the impression there are some really smart people here, able to think outside the box kind of smart, just the right place to seek a solution to my not reading the name plate on the inverter...

    the sine wave of a trace inverter can be roughly described as an aztec pyramid, while not totally smooth, slightly pixelated, but seen by all things electric as a full sine wave.

    now its here where i start guessing, is that frequency of "pixelation" something that can be used to boost 108vac to 115-120vac? at 4000va continous?

    i am way over my head here, suggestions please?
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Have you considered an autotransformer? This will be the cheapest way of achieving what you need and will be relatively compact due to the small voltage increase required. Any transformer manufacturer should be able to advise you.

    [​IMG]
     
    Last edited: Dec 7, 2014
  3. maj113

    Thread Starter New Member

    May 26, 2012
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    thank you for that suggestion, ha! you included my favorite word, "cheapest", perhaps you have a recommendation on mfg or company?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A 108v to 12v buck boost transformer should work, but 4Kva is fairly high, either way.
    Max.
     
  5. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Most transformer manufacturers will make custom transformers but despite being custom they are not usually expensive. Just search on Google and get a few quotes.
     
  6. #12

    Expert

    Nov 30, 2010
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    I have some disagreements. 4KVa is not a small transformer, and transformers are not cheap, from my perspective.

    Another way to do this is to use a 108 volt to 12 volt transformer and place the secondary winding in series with the 108 volts to boost its voltage (wire it as an auto-transformer). I have done this with the 12VAC winding placed to buck the 125 volts at my house down to 113VAC so it doesn't burn out my HID lamps so often. Of course, you are not going to find a 4KVA transformer rated for 108V to 12V, so you are back to the custom winding job, and an auto-transformer is the better option than the 2 winding transformer.

    Probably not enough coffee today. I seem to be rambling about unimportant ideas.
     
  7. Brownout

    Well-Known Member

    Jan 10, 2012
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    Many appliance transformers have 120V and 108V primaries. Just thinking out loud here, if you connect to the 108V leads, you should get 120V from the 120V leads.
     
  8. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Pretty easy to make one yourself.

    Just use a common 115:12 transformer set up as a boost unit by putting both sets of windings in series. Nice part is you are only transforming the 12 volts so for the full 4 KVA load you would only need one rated for around 400 va to get you into the normal 120 VAC output range.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As in post#4 ;)
    Max.
     
  10. #12

    Expert

    Nov 30, 2010
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    As in post #6. ;)
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    How is that done without passing the full current as in a buck type implementation?
    Max.
     
  12. #12

    Expert

    Nov 30, 2010
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    TCM has the right idea, just a bit short on math.

    4KVA @ 108V = 37 amps
    12 VAC x 37A = 444 watts.

    A 12V transformer wound for 450 watts should have large enough wire in the secondary to resist smoking.
     
  13. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Basic transformer theory. The 12 volt winding will be carrying the amps load for the added voltage step up not the 115 winding side.

    In this case its only transforming the power for the the 11.26 volt gain at at most 34 amps peak load thus only needs to be sized accordingly which works out of being just under 400 VA.
     
  14. tcmtech

    Well-Known Member

    Nov 4, 2013
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    My math is correct.
    Inverter capacity stays the same.

    4000/120 = 33

    33 * 11.26 = 373

    108 volts at 37 amps would go in but 4 of them go down the 108 side get transformed into the 11.26 extra volts leaving the other 33 to go up the 11.26 side to come out just short of 120 VAC.
     
  15. #12

    Expert

    Nov 30, 2010
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    Darn, missed again. :mad:

    I'm not coming back until I get good and awake!
     
  16. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Could be worse. My boss argues with me that I can't be good at power electronics and electrical systems because I am not so hot at computer networking or programming.

    ????????????????:confused:
     
  17. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    A 4kVA toroidal autotransformer that is only stepping up 12V would be neither particularly large nor expensive. I recommend that, unless the OP knows what he's doing, he should get one made; the manufacturer will do all the calcs.
     
  18. Brownout

    Well-Known Member

    Jan 10, 2012
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    If you use a transformer, you want to size it to the load and not the converter. So, for example, if your load is only 500 Watts, then you only need a 500 Watt transformer, and not a 4KVA one. As always, you want at least 25% margin when sizing your transformer.
     
  19. maj113

    Thread Starter New Member

    May 26, 2012
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    hey all wow thanx for all the input ! ! ! now i get to really show how little i know of transformers, brownout sez size it to the load +25% , lets say i have 5, 15amp, branch circuits fed from the 'trace' , 15ax120v=1800 , i could set 5, 1.8kva units ?? oops now i lost me, the upside of that 5 smaller units is when the smoke gets out of one, the system is not completely down.... what i do know is all this 'lektric' stuff runs on smoke, let the smoke out an it quits workin'........

    now tcm has me thinkin "wall warts", there are some big chunky 120-12/15vac units out there, an his math in #13 and #14 sez bout 400va should work, might be an easy score on the cheap like from ebay or amazon, one on each branch ckt at the distribution panel......

    #12 in #6 mentioned 125vac was hard on his transformer fed hid lights, i think i shall examine my proposed loads, thanks for the heads up.
     
  20. Brownout

    Well-Known Member

    Jan 10, 2012
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    15A*120V*5 = 9KWatts. You're converter is only good up to 4KWatts. You can only run two of your 15A circuits.
     
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