Computing output of bucking coils...

Discussion in 'General Electronics Chat' started by thrival, Jan 29, 2013.

  1. thrival

    Thread Starter New Member

    Nov 18, 2006
    I am trying to understand the effects of series bucking coils on V & I output. Apparently the bucking configuration was used in the early days of radio, but with the introduction of IC's are all but forgotten. My interest is their potential for stepping down voltages in the most direct and simplistic fashion. For example: (see attached.)

    My point is it would be useful to use bucking coils to step down voltages to approximate levels to preserve current rather than burn it up in resistance networks or even voltage regulators. Anyway I'm trying to learn the rules that inductors follow in such arrangements. Thanks for any insights or formulas.
  2. Papabravo


    Feb 24, 2006
    In the drawing you have given us, there is no reason why there should be any voltage at all between the midpoint of the two inductors and the ground symbol. If the ground symbol in your drawing and the AC source have a common ground that would be a different story.

    The actual idea is that secondaries in series with the same polarity would add together. For example if I have a 5VAC secondary and an 8VAC secondary and they are in phase, I can get 13VAC across both of them. If I wire them together as you have drawn then I get 3VAC across the pair.

    How you convert the 3VAC to DC should be straightforward.
  3. thrival

    Thread Starter New Member

    Nov 18, 2006
    Dear Papabravo:

    Thank you for your reply. OK I get your point about secondaries but in this case I'm not using any. We could use either side of the AC line as a reference though; I'm OK with that.

    (Note: I've looked at AAC's transformer winding tutorial, but it's dealing with primaries AND secondaries, whereas in my example I'm using series inductors only.)

    So are you saying that under ordinary circumstances, if equal and opposite coils (in series bucking configuration), are plugged into an AC line, there will be no current flow, and nothing can be drawn off a center tap to an actual ground? That would be interesting and while I see it as being mathematically correct, still rather amazing in practice. How would the utility perceive such a hook-up? Would the inductor size matter? (I would expect adding or subtracting a turn would increase or decrease V not unlike an autotransformer.)

    What I was looking for was a V step down, say by half. Then another such arrangement to reduce by half again, etc. I'll admit it's an odd method, possibly nothing to be gained, but I wouldn't know unless I asked.