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inductance question

Discussion in 'Electronic Design' started by Yzordderrex, Jun 14, 2007.

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  1. Yzordderrex

    Yzordderrex Guest

    I have 50' of wire and I want to build an air core inductor and
    maximize the inductance. Is 1 big turn going to give me the most
    inductance?

    regards,
    Bob
    N9NEO

    Just say NEO!
     
  2. Fred Bartoli

    Fred Bartoli Guest

    Yzordderrex a écrit :
    NEO! It isn't just one big turn :)

    What you're after is called a Brook's coil.
    The very nearly optimal coil has a square section (a x a), internal
    diameter 2a (and consequently external diameter 4a ).
    You'll have to solve this for your wire length and diameter.

    Inductance value is L = 2.55E-9.a.N^2 (in H) with a given in mm.
     
  3. "Fred Bartoli"
    Sweet!
     
  4. Tim Wescott

    Tim Wescott Guest

    Expect lots of interwinding capacitance.

    A one-turn coil, by the way, makes a nice antenna when it gets to be one
    wavelength in circumference -- think "loop antenna".

    --
    Tim Wescott
    Control systems and communications consulting
    http://www.wescottdesign.com

    Need to learn how to apply control theory in your embedded system?
    "Applied Control Theory for Embedded Systems" by Tim Wescott
    Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
     
  5. D from BC

    D from BC Guest

    Square section?? Is that why those wallwart transformers have square
    bobbins?


    D from BC
     
  6. kell

    kell Guest

    square in cross section. wound round.
     
  7. He'll get more inductance by tightly bundling those turns
    than by winding them is a single layer solenoid of the same
    diameter. The bundled form provides tighter coupling
    between the turns, that most closely approaches the turns
    squared effect on inductance.

    The inter winding capacitance will be higher, also. I don't
    know exactly what the optimum relationship between bundle
    diameter and average turn diameter for optimum inductance
    per wire length, but I am guessing that the bundle cross
    section diameter needs to be quite a bit less than the
    average turn diameter.
     
  8. The Phantom

    The Phantom Guest

    Just one of many web pages on the Brooks coil:

    http://home.san.rr.com/nessengr/techdata/brooks/brooks.html

    Making the cross section circular or hexagonal rather than square increases
    the inductance by about 1%; hardly worth doing.
     
  9. LVMarc

    LVMarc Guest


    If you want to get the highest inductance and the highest "q" and at the
    highest possible frequecny:

    then you want a shape that incloses the maxium volume, with a minimium
    shaped wire envelop I geomtery tis wold yield a sphere. not so goo for
    coils.

    the next shapoe woulb be apporx 2:1 right hand clynder shape,with
    several turns, and the angle of wires about 42 degrees....

    Marc
     
  10. 1% more is more. By the way, do you have a reference that
    confirms this magnitude of improvement for a round copper
    cross section? I would have guessed a couple more percent,
    because it reduces the number of longest turns (that use the
    most of the total wire length per turn) and the shortest
    turns (that enclose the least area) and increases the number
    of turns near the average length, Reducing the shortest flux
    line that encircles all the turns, as well as reducing the
    distance between each turn and its average neighbor,
    improving their flux linkages. I would be a bit surprised
    if all those slight but compounding factors added up to only
    an additional percent.
     
  11. D from BC

    D from BC Guest


    Right hand cylinder?

    Is it like this

    | ----/////////-
    1 ---/////////-- 42deg angled windings
    | --/////////---
    <-----2---->
    D from BC
     
  12. The Phantom

    The Phantom Guest

    Courtesy of Google, I see that Brooks inductors were discussed on SED back
    on August 25, 2004, where you asked Winfield about circular cross sections.

    Winfield mentioned a "definitive" study of Brooks inductors, but apparently
    nobody has ever posted it.

    I'm going to take a chance that your email address is jpopelish at rica dot
    net and send it to you.
     
  13. I put up with all the spam just to make it simple for nice
    people like you to send me stuff. Thanks.
     
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