Ac to Dc converter

Discussion in 'General Electronics Chat' started by Neptune, Feb 13, 2014.

  1. Neptune

    Thread Starter New Member

    Dec 16, 2013
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    I run 12 amps through an electromagnet that's 5 ohms. I have a large transformer core, large gauge magnet wire, a high current/high voltage bridge rectifier, and high voltage capacitors. What I can't seem to figure out is the amount of turns I should have on my transformer for both the secondary and primary. I can't seem to wrap my head around the dynamics of rectifying Ac to dc under a load. My main Ac supply is 120 Vrms.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The average for a large number of mains transformers is ~ 2.5turns/volt.
    If you have an existing transformer that has a known primary winding or any winding for that matter.
    Powering this winding with the correct voltage and if possible place ten turns on and measure the result, this will give you the t/v necessary.
    Toroidal types are generally slightly less t/v.
    Are you attempting to build a complete transformer?
    Max.
     
  3. Neptune

    Thread Starter New Member

    Dec 16, 2013
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    No, I disassembled a microwave transformer.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Does it still have the primary? If so you can do the test I mentioned, I would hazard a guess the MWT is a little less on the t/v than many transformers out there.
    Your secondary voltage/current for your application has to be known either by calculation or evaluation the application on a separate power supply first.
    Final DC will be 1.414 of the applied AC.
    Max.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    If you can use unfiltered rectified AC (bridge rectifier with no filter) through your electromagnetic then the average DC voltage will be (.636/.707) * Vrms of the output voltage. Doing that would be more efficient, generating less resistive loss in the transformer windings.
     
  6. Neptune

    Thread Starter New Member

    Dec 16, 2013
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    The primary is still on it, I saved it. How does the turns/volts = turns/volts rule apply to this sort of thing? I surprisingly have little knowledge of this sort of thing apparently.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you know the AC voltage that you require, in order to obtain the number of turns required for the secondary, place a few known number of turns on, gauge does not matter at this point, measure the resultant voltage and extrapolate the number you need, use a gauge for the final winding that will support the estimated current.
    Max.
     
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