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Magnetic force in a transformer?

Discussion in 'Electronic Design' started by Phil Hobbs, Dec 15, 2003.

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  1. Phil Hobbs

    Phil Hobbs Guest

    In the absence of secondary current, what you have is an electromagnet
    with a piece of iron nearby. You already know what that does.

    In the presence of secondary current, where does the secondary current
    come from? Right. So you know what that does too.

    Good luck on the rest of your problem set.

    Cheers,

    Phil Hobbs
     
  2. Jon.boston

    Jon.boston Guest

    If I had a simple transformer Core with Primary on the left and
    secondary on the right. If I sliced the core in half seperating the
    primary from the secondary would the two sections repel or attract?

    Jon
     
  3. Adam S.

    Adam S. Guest

    If the primary is on the right side and the secondary on the
    left side then the sliced cores will repel, if the primary
    is on the left and the secondary on the right then the cores
    will attract, (or is it the other way around ?)

    Adam
     
  4. It depends on whether the windings are wound CW or CCW and whether you
    are in the northern or southern hemisphere.
     
  5. R.Legg

    R.Legg Guest

    The physical forces always act to attempt to shorten the magnetic
    path.

    You talk about a 'simple' transformer with windings on the left and
    the right. I have to assume you are describing a U-U structure or a
    torus, both fairly special structures in real life, and seldom wound
    as you describe.

    For a start, for a transformer to be a transformer, the circuit must
    be completed - this usually involves a load and a source. Without
    either, you have a mock-up-only science project, or an unneccessarily
    complex inductor.

    Once the circuit is complete, you can actually have transformer
    action.

    The shortened magnetic path could be achieved in your 'simple' circuit
    if the ends of the winding structures were closer together - a force
    will therefor be applied to attract these ends together.

    If they were wound side by side on the same axis, the force would be
    exerted to pull distant ends together - if this is equal in all
    directions the result is force impelling the coils towards each other.
    As few things are really as equal or symmetrical as they seem, in real
    life the axial winding will try to bend, under extreme applications of
    external energy.

    This effect can be seen for common-mode impulses applied to cheap
    common-mode EMI chokes wound on E-E structures, using partitioned
    bobbins. A hefty common-mode surge (lightning) will cause them to fold
    over like a sandwich made from a single slice of bread - folding axis
    being the core joint in line with the bobbin's partition.

    RL
     
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