DC-AC Inverter

Discussion in 'The Projects Forum' started by assassin, Dec 27, 2008.

  1. assassin

    Thread Starter Member

    Dec 27, 2008
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    Hi..I have design an inverter that input is 10VDc , output is 220VAc and the output power is 20W... But i cant design the transformer i have calculated the winding numbers but i cant calculate the inductance. it is requiered because i have to simulate it and i need that inductance value... can anyone help me pls? circuit image is this..is there anything wrong about the circuit? i have tried lots of numbers for transformer windings but i didnt work out..
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    What is Q3 doing?
     
  3. assassin

    Thread Starter Member

    Dec 27, 2008
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    Q2 and Q4 is the power BJTs and they are used for + and - alternances. Q1 and Q3 are used for producing Ib base current to Q2 and Q4.. Q3 is on when Q1 off and vice versa...
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    I think you have Q3 upside-down. Emitter, not the collector, should be to +V for a PNP.

    Ken
     
  5. assassin

    Thread Starter Member

    Dec 27, 2008
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    i did it and it is almost the same... i have got problem with the value of the transformer windings because i get the signal from the output but it is not what i want.. it is too low about 1-2V...i need 220V...what do u think about it.. this circuit drives me crazy man..
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Do you have a center-tapped transformer in your library?

    You're using two separate transformers instead of a center-tapped transformer. That's going to goof things up.

    Find a center-tapped model, and then try starting out with 1h for both windings in your primary, and 22h for your secondary winding.
    [eta]
    Blocco and KMoffet are correct; the emitter of Q3 must go to +12V. Otherwise, you'll have minimal conduction of Q4, and your output will look very lop-sided.
     
    Last edited: Dec 27, 2008
  7. assassin

    Thread Starter Member

    Dec 27, 2008
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    no there is not a center-tapped transformer in my library... and i cant use another simulation program i have to do it with this :( it is a school project.. cant i do it without using a center-tapped transformer.. isnt it working what i did?
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    If you don't have a center-tapped transformer in your library, and you can't add one, you will need to devise a way of reversing the current flow through the single primary of a single transformer.

    An H-bridge configuration will do that for you. Research H-bridges.
     
  9. assassin

    Thread Starter Member

    Dec 27, 2008
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    Ok.Thanks a lot.. i made it before but i will do it again.. but could u help me about how i can calculate the inductance? how can i find that formula..if u have a source about transformer design could u send it to me?
     
  10. bertus

    Administrator

    Apr 5, 2008
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  11. assassin

    Thread Starter Member

    Dec 27, 2008
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    i have been reading it for hours.. and i cant find anything :( pls someone give me the primary and secondary inductance formulas..
     
  12. trajcetr

    New Member

    Dec 26, 2008
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    I have expiriance for this type of dcac inverter for 12v/220v use standard ac transformer 2x12v example 120w for this data sheet
    or 24/220 use 2x24v/220w ,if you have any questation send me mail
     
  13. assassin

    Thread Starter Member

    Dec 27, 2008
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    did you get my mail or i write my problem here?
     
  14. assassin

    Thread Starter Member

    Dec 27, 2008
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    pls someone send me that inductance formulas i cant find anywhere.. i'm starting to doubt that there is no formulas for this:rolleyes:

    and how can i do a center-tapped transformer with two seperate transformers like in my circuit..what is wrong with transformer in my circuit?
     
  15. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Inductance depends on number of windings, and the material of the core (and maybe some other not too important things). You have to know what core you will use to know the inductance.

    Or the other way, you set the inductance you want to use from the other parameters like switching frequency, and then you find suitable core.
     
  16. Audioguru

    New Member

    Dec 20, 2007
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    It is such a simple square-wave inverter. Don't design the transformer, buy one.
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    Q3 is backwards, you need to connect emitter to minus and add a resistance on the collector. You are back biasing the transistor, an unpredictable state.

    You could reverse it a bit like so...

    [​IMG]

    Use 6.2V zeners. They will prevent shoot through. I have never tried this circuit.

    One thing that stood out was polarity of the transformer, you need to be very careful there.
     
    Last edited: Dec 27, 2008
  18. Wendy

    Moderator

    Mar 24, 2008
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    One other thing, with transformers, you shouldn't need inductance. Counter EMF should swamp it.
     
  19. assassin

    Thread Starter Member

    Dec 27, 2008
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    ofcourse i will buy one but it's a school project and i need that formula.. i have to write it in simulation program (Pspice)...
     
  20. assassin

    Thread Starter Member

    Dec 27, 2008
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    Thank u man for the circuit...i'm doing it now.. but inductance is the head of my problems.. i dont know how to calculate it... if u have a simu program can u draw the circuit and send me the results pls... i really need this...
     
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