making diy transformer

Discussion in 'General Electronics Chat' started by green90, Mar 18, 2016.

  1. green90

    Thread Starter New Member

    Sep 3, 2015
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    i want to built a step down tr (230v to 12v) by high pressure sodium fixture chock buy combining 2 of them one for primary and one for secondary
    note: chock has about (250-300)turn
    but how i can connect primary coil to main(230v 50hz)and not happen short circuit ??????


    chock.jpg
     
  2. #12

    Expert

    Nov 30, 2010
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    All transformers rated for 230v to 12v have their primary connected to the main. Why would yours short circuit?
     
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  3. green90

    Thread Starter New Member

    Sep 3, 2015
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    truly i make test by only connecting primary choke(coil) to main ____ is 250 _300 turn coil enough for 230v 50hz primary to not be short cct????
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. #12

    Expert

    Nov 30, 2010
    16,261
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    Absolutely no!
    If you want to make your own transformer you must calculate how many turns are required for that core.
    Start with the millihenries of the choke and the current when the choke was in the light fixture. You can calculate these from the information page for the light fixture.
    For example, If 300 turns made 35 millihenries you can calculate how many turns you need to get the inductance up to the right amount to limit the main current. Then you can decide a wire size to carry the current required for the power you are designing for. The cross sectional area of the primary winding should be equal to the cross sectional area of the secondary winding.

    That's all I have for this project.
     
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  6. green90

    Thread Starter New Member

    Sep 3, 2015
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    thank you
    its power factor .45 as written on it ,,, its used for 400w sodium balb . current is about 4A and after connecting capacitor parallel will decrease to 2A but i didnt find millihenric for it
     
  7. #12

    Expert

    Nov 30, 2010
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    It looks like 183 millihenries to me.
     
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  8. green90

    Thread Starter New Member

    Sep 3, 2015
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    how did you calculate ???? and do you know light fixture starter (ignitor )prevent choke from short cct when conduct only short while using diac thyristor ...and also hpsv bulb resistance will decrease to zero after conducting
     
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