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40-0-40 @8A+8A transformer to 40vdc @ 16A - Possible?

Discussion in 'Electronic Basics' started by RayGilbert, Dec 20, 2003.

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  1. RayGilbert

    RayGilbert Guest

    Hi,
    Is there a proven method to rectify a 40-0-40 hardwired centre tapped
    transformer using both of the windings for fairly high current
    application.
    I would prefer a method with little or no smoke and absolutely no loud
    bangs :)
    TIA
    Raymond Gilbert
     
  2. You will have to find a way to seperate the two windings, ie the centre tap.
    If the outcoming center tap is just one cable (Not two wires twisted etc)
    you will find that a lot more work. If it is as is common two wires twisted
    they must be seperated and then you can join the windings to run them in
    parallel for the extra current. Each winding should be connected "start to
    start" and "finish to finish".
    If you should get it wrong there would be no output.
     
  3. It's pretty straight forward....

    A full wave center tapped design will give you the 16 amps or more.
    (Each half of the transformer is alternativly used at twice it's rated
    current for half the time.)
    Be sure to use 2 WAY over 16 amp diodes, and the voltage rating should not
    be less than 200.
    [The center tap is a common... Ground or power, depending on which way you
    install the diodes.]

    --
    *
    | __O Thomas C. Sefranek
    |_-\<,_ Amateur Radio Operator: WA1RHP
    (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

    http://hamradio.cmcorp.com/inventory/Inventory.html
    http://www.harvardrepeater.org
     
  4. RayGilbert

    RayGilbert Guest

    Thanks for your reply Rheilly,
    I don't think that the windings can easily be accessed as it is a
    sealed toroidal transformer.
    Kind regards
    Raymond Gilbert
     
  5. Then you are stuck with DC transformation. A two phase switching buck
    regulator could transform the rectified and filtered 113 volts to 40
    while increasing the current from about 6 amps to 16 amps and you get
    regulation and possibly current limit to boot. But it is quite a
    project.
     
  6. RayGilbert

    RayGilbert Guest

    Thanks for your reply Thomas,
    Looks promising then.
    What would be the theoretical rectified voltage (peak and RMS).
    Would I connnect as follows

    40v > D1 anode D1 cathode > smoothing > load
    0v > common (Ground)
    40v > D2 anode D2 cathode > smoothing > load

    cathodes connected together before smoothing.

    I tried some ASCII art but I couldn't understand it myself.

    Kind regards
    Raymond Gilbert

     
  7. cpemma

    cpemma Guest


    Low down this page: http://www.plitron.com/Pages/technote.htm
     
  8. It all depends on your load and "smoothing" capacitor values.

    Peak voltage is roughly 1.4 times the RMS value of the transformer.
    So unloaded you could see greater than 56 volts.
    Adding load will lower the voltage until at 16 amps or so it will be 40 VDC.
    It is NOT a regulated voltage.

    --
    *
    | __O Thomas C. Sefranek
    |_-\<,_ Amateur Radio Operator: WA1RHP
    (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

    http://hamradio.cmcorp.com/inventory/Inventory.html
    http://www.harvardrepeater.org
     
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