Using ferrofluids to design more efficent inductors?

Discussion in 'General Science' started by retched, Apr 27, 2011.

  1. retched

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    I was watching a video on ferro-fluids. These are liquids that react to a magnetic field.


    If made properly, the ferro-fluid shows a 3-dimensional representation of the magnetic field.

    I couldn't help but to think how this could help in the design/construction of inductors. Using the fluid, unlike the iron-filing-on-paper method, you get a great map of where EXACTLY the fields strongest points are. This could help with coupling. It could also help with mounting. By "aiming" the weakest part of the field toward the most sensitive components, you can build more reliable systems.

    Take a look:
    http://www.youtube.com/watch?feature=player_embedded&v=tGJjSVI5V0M
     
  2. someonesdad

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    Ferrofluids have been used for decades in rotating vacuum feedthroughs (that's where I first came across them about 35 years ago). They have to use a low vapor pressure oil, so that makes them only for use in "crummy" vacuums (at least for us ultra-high vacuum snobs :p). Unfortunately, the ferromagnetic particle density makes them opaque, so you can only see the external effects.

    The video was interesting. I'm sure someone somewhere has given an analysis for those cone-shaped projections. It won't be a trivial problem because the ferrofluid affects the field and surface tension and gravity are at play too. But there's probably an explanation in an old Scientific American article somewhen...
     
  3. Kermit2

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    Someonesdad is right about this.

    The magnetic field will NOT be the same size or shape once the magnetically interactive substance is removed. This is true for any FERRO magnetic substance. The iron will always modify the size and shape of the field. Any ideas of magnetic shape or direction you gather from the ferrofluids shape and size will only apply while the fluid is there, and not when it is removed.
     
  4. retched

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    There are optical ways to view a magnetic field, and I agree that the fluid does affect the strength of the field,

    BUT,

    the shape of the field should stay the same.

    Therefore you still get a "map" of the strongest and weakest areas of the magnet, itself.

    Does that negate the possibility that any useful information can be extracted from a ferro-fluid method for determining the best winding techniques and/or placement?
     
  5. someonesdad

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    Personally, I've never see ferrofluids use for such a task, although that doesn't mean that such tools don't exist. Here's a place that sells transparent films with a colloidal suspension of ferromagnetic particles (nickel) to help view fields. In industry, though, it was just much easier to use an electronic instrument to quantify the fields. The instruments from F.W. Bell were typically used where I used to work. The above link also has a number of instruments that can make magnetic field measurements.

    Considering that it's pretty straightforward to find a variety of Hall effect sensors that can measure fields, even the hobbyists can get in on the action if they want. Calibrated measurements are a bit harder. It has always bugged me as a hobbyist that I can't walk into Wal-Mart and pick up a nice instrument for measuring magnetic fields for $29.95. :p
     
  6. retched

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    I am having the urge to fill a test-tube with ferro-fluid and wrap the test tube in a coil of copper... even coupled transformer style.

    I am wondering how, if given the chance, the "core" would shape itself under load. And if that new shape has a positive(higher efficiency) effect on the inductance, or if the fluid's "natural 'under-field' shape" destroys the flux.
     
  7. nsaspook

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  8. retched

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    It isnt the conductivity of the material as a whole, but allowing the flux altering material to "align" itself.

    [ed]
    Its early... lemme think on this..
    [/ed]
     
    Last edited: Apr 29, 2011
  9. shortbus

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    Last edited: Apr 29, 2011
  10. nsaspook

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    I don't think the inductance would be very stable, as a signal current is passed thru the inductor coils it would alter the flux and change the alignment of the ferrofluid unless the forming flux was many times larger than the signal flux.
     
  11. retched

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    Providing a bias to the signal to form the flux....

    ..I dunno...my brain feels like sludge..
     
  12. nsaspook

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    Once you have the flux-inductor then you need the flux-?
     
  13. retched

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    Capacitor! ;)
     
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