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Litz wire

Discussion in 'Electronic Design' started by Tim Williams, Feb 19, 2010.

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  1. Tim Williams

    Tim Williams Guest

    Who sells this stuff (without paying for miles at a time)?

    I'm especially interested in stupid thick stuff, like, as large as 8AWG
    equivalent. Nebraska Surplus for instance doesn't stock wire like this.

  2. Tim Williams

    Tim Williams Guest

    I do sometimes, but only for small things. I'm contemplating 10A at 1MHz,
    so it needs to be pretty fine = way more strands than I'd want to deal with.

    I actually have some copper rope, which is about 1/4" diameter and looks to
    be made of 28AWG or so. I don't remember how many strands it is, but if I
    guess the rope is wound from 7 strands of 31 strand twist, that's 7*31 =
    217. If 28AWG is good for ~200mA, 217 strands should be good for 40A, which
    sounds about right, I'd call it 8 or 10AWG equivalent. I salvaged this
    stuff from some old motor driver, which used a spool of this stuff for
    air-core inductors.

  3. Tim Williams

    Tim Williams Guest

    Well, I've got the rope stuff I mentioned earlier, and I've taken apart Sony
    transformers (which were wax impregnated, not varnished!) which used litz.
    Just a twisted bundle, not properly woven, but I'm not that picky.

  4. I did a web search last week for some for a power converter
    transformer. 600+ strands of AWG 46 wire for something like $1/foot in
    small quantities. You could braid about five of those together..
    (I'm sure you can find it as easily as I can).

    Best regards,
    Spehro Pefhany
  5. Pick a gauge, buy the mag wire, and make your own. It is not that hard
    at all. Properly braiding out a custom length of Litz wire is no harder
    that winding your own custom pot core transformer bobbin. One just has to
    set one's mind to it, and accomplish a simple task without assigning
    undue difficulty to it without even trying.

    Can't be any harder than macrame. You can actually come up with better
    stuff than you can even buy too.

    The stuff you refer to sounds like it would not be a cheap per foot
    price, even if you were buying a whole spool. Probably better to fashion
    a double long length, then cut it in half when you are ready to use it.

    What is the application , and the length of the run? Or is it needing
    to be long enough to be a primary winding?

  6. The problem is that it not being constructed from individual mag wires,
    it is "seen" as a single strand to the current flow, and having only ONE
    skin. The litz configuration requires the wire be discreet from each
    other with the exception of the termination points.
  7. No. The wire strands have to be mag wire, which segregates them from
    each other, allowing the skin effect to be taken advantage of. Without
    strand segregation, it becomes a single strand, from the POV of the
    current flowing in it, with only one skin for the entire mass.

  8. One can take multiple pieces of a smaller litz, and increase the
    effective gauge. No need to unwrap the individual segments.
  9. Tim Williams

    Tim Williams Guest

    See the beast of a transformer in this thing?
    That's one use of the rope I found (where the plastic covering is peeled
    away, you can even see the cool ropey ropeness of it -- pretty!).

    That's 20 turns, and each turn is maybe 8" long, or 160" = 13.3' total. If
    it's actually 231 strand as I speculated earlier, that's 3kft, more than
    half a mile of 28AWG.

    Now, if I build more of these, I don't need quite this many strands since
    it's only running at 20kHz. But the 1MHz thing I mentioned elsewhere needs
    wire at least this fine.
    Neet, this calculator suggests I want 242 x 36AWG to get something
    resembling 12AWG.


  10. The definition of Litz relies on the fact that the strands are
    electrically segregated from each other between their terminus points.

    It does NOT HAVE to be specially braided or woven. The thermal strip
    wrapped stuff DOES qualify as litz, depending on length and intended
    application, and I have bought the MWS product before.

    The proof? I made several of my own Litz configuration primaries for
    transformers and the proof is in the pudding of the observed performance
    characteristics, even at lower frequency switcher supply cycle rates. The
    fact is that it definitely works to segregate several strands of
    conductor on short runs of AC pathways or in inductors and chokes and
    transformer windings. Trial and error with gauges and strand count do
    more to optimize the result than ANY specialized, presumed to be required
    braiding or weaving. The segregation is the key to increasing surface
    area within a given cumulative "gauge".

  11. STOP top posting.

    If it is non-segregated "rope" as you call it, it is no different than
    welding cable and is merely being used as a flexible, high current link
    to the winding or as the winding media itself, but there will be NO "Litz
    function" if the individual strands are not isolated from each other
    electrically along the length of the conductor.

    All the strands of Litz type wire co-conduct *apart* from each other,
    EXCEPT at the ends where they are ALL terminated at the same node.

    Other wise there is no litz configuration and there will be no litz
    effect or function taking place. The "rope" or cable as it is properly
    called, will have a single "skin effect realm" that surrounds the entire
    bundle and NONE of the inner wires will carry any current in high freq rf
    conduction. With segregated wires, each has their own skin and the total
    amount of conducting copper in an rf conduction setting is an order of
    magnitude greater. Of course strand gauge has an effect on that and the
    improvement will be less with larger strands, but they ALL MUST conduct
    separate from each other except at their common endpoint nodes, or there
    is no effect.
  12. Tim Williams

    Tim Williams Guest

    I see you don't view links. The wire is clearly individually insulated,
    which is what everyone else in this thread understands by "litz", except
    yourself, as you have stated six times over. It's a good thing you're in
    everyone's killfile.

  13. I looked. That is NOT #28 at 231 strand count, and your calculations
    are wrong as well. You probably used bare copper diameters, when you
    should be using single strength mag wire diameters.
    Goddamned top posting retard. Six times over I stated that it had to
    be individually insulated, dipshit, so it is not "except yourself" you
    dippy little bitch.

    It isn't fucking called rope either.

    And your formula result is almost off by a factor of two! 12 Ga result
    does not require the strand count you gave.
  14. 231 strands of #28 would be bigger in diameter than that wire appears
    to be. Even 231 strands of #38 or #43 would be pretty big. No way that
    those are #28 strands, or if they are, there are not 231 of them.

    Use some common sense. 231 strands of #28 single strength mag wire has
    a bundle diameter of nearly 3/8"!

    Your #12 ga arrival math is off too.

    D=Diameter of a bundle of wires
    d=diameter of a single strand in the bundle
    N=Total number of wires.

    D= 1.55 x d x (Sq rt of N)

    The #12 is about 0.083" in diameter without a wrap. The 242 strands of
    #36 you stated is 0.0056" in diameter, which is for single strength mag
    wire, and comes out to 0.135"

    So, the lesson is DO NOT forget the insulation.
  15. Ross Herbert

    Ross Herbert Guest

    On Fri, 19 Feb 2010 21:14:27 -0800, life imitates life

    :On Fri, 19 Feb 2010 16:18:49 -0600, "Tim Williams"
    :>I actually have some copper rope, which is about 1/4" diameter and looks to
    :>be made of 28AWG or so. I don't remember how many strands it is, but if I
    :>guess the rope is wound from 7 strands of 31 strand twist, that's 7*31 =
    : The problem is that it not being constructed from individual mag wires,
    :it is "seen" as a single strand to the current flow, and having only ONE
    :skin. The litz configuration requires the wire be discreet from each
    :eek:ther with the exception of the termination points.

    I hope you don't mind a little bit of layman's interpretation as an assistance
    to the OP but what you mean by "mag wire" is that each individual strand which
    makes up the total x-sectional area of the litz conductor MUST be insulated from
    every other strand. If the strands aren't insulated then the skin effect will be
    the same as if a single strand of the same overall x-sectional area had been
    used - and this is no good for high frequencies.

  16. Exactly. I do not word things well on the fly. I do far better as a
    proofreader of other's works or even my own work, upon subsequent
  17. amdx

    amdx Guest

    No need to do trial and error, Here's a table that gives recommended gauge
    with regard to frequency.
    See Table B.
    Same thing in pdf. PDFs/Frequency_Chart_3.01.13.09.pdf

    Regarding "ANY specialized, presumed to be required braiding or weaving":
    This is used to equalize proximity effects which equalizes currents in the
    individual wires.

    Quote from;
    "The objective of twisting or weaving litz wire, as opposed to just grouping
    fine conductors together, is to ensure that the strand currents are equal.
    Simple twisted bunched-conductor wire can accomplish this adequately in
    situations where proximity effect would be the only significant problem with
    solid wire. Where skin effect would also be a problem, more complex litz
    constructions can be used to ensure equal strand currents. Thus, in a
    well-designed construction, strand currents are very close to equal."

    There is a great deal of information available about the use of litz wire,
    if you have the math ability
    you can become an expert in a couple of days!
  18. legg

    legg Guest

    It might serve if you can decouple the strands.

    Shake it loose and bake it to form an ~oxide layer on the individual
    strands. Doesn't have to be an insulator as such, just a poor
    conductor to adjacent wires.

    The actual aim of the 'twist' is to have strands in any particular
    bundle or strand at near-right angles to those on the opposing
    surface, as the twist pattern is scaled up.

    If the twist direction is reversed on each level of build-up, surface
    strands will always appear to be pointed in the approximate direction
    of current flow, and the structure itself will not 'bind'.

  19. amdx

    amdx Guest

    It's just a matter of good, better, and best.
    Best would be properly braided* and would have the least AC resistance.
    *I'm not sure braided is the proper term. Each wire needs to have equal
    exposure to all positions in the bundle.
  20. amdx

    amdx Guest

    The copper rope is not long enough? We've got some discard litz wire,
    but not nearly that thin or as many strands. We use it to make high Q
    coils to detect the nuclear magnetic moments of protons spinning in
    the Earth's B field. Frequencies a bit above 2kHz. And lots smaller
    currents. Well the same coils polarize the spins, but that's 3 amps
    at DC.

    George H.

    Hi George,
    Is this used in a magnetometer?
    There is a thread on with the
    subject: Carl and Jerry Magnetometer, that has a discussion
    about about picking up the precession of the proton as it
    returns back to alignment with the earths magnetic field.
    I found it very interesting, probably because I knew zero
    about the subject.
    If you have anything to add to that thread, please do so.
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