Litz wire
in [Design]
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From: life imitates life on 21 Feb 2010 20:15 On Sun, 21 Feb 2010 18:57:34 -0600, "amdx" <amdx(a)knology.net> wrote: > >"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in >message news:3kh3o5la77d3spc30sp4vdb381lp5hluuh(a)4ax.com... >> On Sun, 21 Feb 2010 17:10:03 -0600, "amdx" <amdx(a)knology.net> wrote: >> >>> As stated before proximity effect is minimized by making every conductor >>>find itself in the same position in the bundle an equal amount of time. >>>Twisting may or may not do that, depends on the amount of conductors >>>twisted. >> >> It also depends on what he stated. If the run is short enough it makes >> no difference. Lower frequencies at lower currents also have less issues >> with the outward EM field push that we all know as "skin effect". >> >> AND the mag field around each individual conductor in a bunch, whether >> Litz woven or not, will be different than that of the solid, so the EM >> field effect claimed to also affect non-woven bundles is not as >> pronounced as you might think. >> >> The wires in the centers of non woven bundles do NOT exhibit the same >> problem that a solid does. It is several parallel fields, not a single >> conduction field. Yet another reason why the effect is still realized >> sans the weave. It is not 100% efficient, from that perspective, but it >> DOES STILL work. >> >> It is a fact. Get used to it. > > I completely agree Jim. > I just went on a rant when qrk said, > " If you're under 1MHz, you're mainly > fighting proximity effect, not skin effect." > I don't believe that, and I think a properly sized bundle of twisted >(insulated wire) >will have a large effect over a solid wire with the same circular mils. >(as Dogmargoodboat said, 3x) > It would be interesting to find what percentage change a twisted litz >would have >over a properly braided litz. I'll bet it's under 20%. > What do you think? > Mike > > So.... what a hoot. You accidentally agreed with me?
From: amdx on 21 Feb 2010 20:34 "life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in message news:hkm3o51tnqql56evft6m5revv2aot0tse0(a)4ax.com... > On Sun, 21 Feb 2010 18:57:34 -0600, "amdx" <amdx(a)knology.net> wrote: > >> >>"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in >>message news:3kh3o5la77d3spc30sp4vdb381lp5hluuh(a)4ax.com... >>> On Sun, 21 Feb 2010 17:10:03 -0600, "amdx" <amdx(a)knology.net> wrote: >>> >>>> As stated before proximity effect is minimized by making every >>>> conductor >>>>find itself in the same position in the bundle an equal amount of time. >>>>Twisting may or may not do that, depends on the amount of conductors >>>>twisted. >>> >>> It also depends on what he stated. If the run is short enough it makes >>> no difference. Lower frequencies at lower currents also have less >>> issues >>> with the outward EM field push that we all know as "skin effect". >>> >>> AND the mag field around each individual conductor in a bunch, whether >>> Litz woven or not, will be different than that of the solid, so the EM >>> field effect claimed to also affect non-woven bundles is not as >>> pronounced as you might think. >>> >>> The wires in the centers of non woven bundles do NOT exhibit the same >>> problem that a solid does. It is several parallel fields, not a single >>> conduction field. Yet another reason why the effect is still realized >>> sans the weave. It is not 100% efficient, from that perspective, but it >>> DOES STILL work. >>> >>> It is a fact. Get used to it. >> >> I completely agree Jim. >> I just went on a rant when qrk said, >> " If you're under 1MHz, you're mainly >> fighting proximity effect, not skin effect." >> I don't believe that, and I think a properly sized bundle of twisted >>(insulated wire) >>will have a large effect over a solid wire with the same circular mils. >>(as Dogmargoodboat said, 3x) >> It would be interesting to find what percentage change a twisted litz >>would have >>over a properly braided litz. I'll bet it's under 20%. >> What do you think? >> Mike >> >> > > > So.... what a hoot. You accidentally agreed with me? I'd rather say you agree with me, and in that case, you sure are smart. Mike
From: legg on 21 Feb 2010 21:44 On Sat, 20 Feb 2010 22:18:28 -0800, life imitates life <pasticcio(a)thebarattheendoftheuniverse.org> wrote: >On Sat, 20 Feb 2010 23:55:18 -0500, legg <legg(a)nospam.magma.ca> wrote: > >>On Sat, 20 Feb 2010 10:58:17 -0800, life imitates life >><pasticcio(a)thebarattheendoftheuniverse.org> wrote: >> >>>On Sat, 20 Feb 2010 09:12:29 -0500, legg <legg(a)nospam.magma.ca> wrote: >>> >>>>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. >>> >>> Bullshit, ya fuckin' retard. >> >>Not so much words on the fly, but flies on the words, it seems. >> >>You could also vacuum impregnate the bundle, if it's already formed >>into position (and if you've got a really good impregnation process >>cooking). >> >>RL > > No, you cannot. It only works with insulated strands. Trying to come >up with an 'insulation on the fly method is just plain stupid. It doesn't really matter when, how, or why insulation between strands is achieved and the voltage levels presented are extremely small, so polymers are really overkill. Note that complete isolation is not required, simply a degree of effective isolation, most of the time, between adjacent inner and outer stranding, as these will swap over, by design. If 80% of the skin current is forced back into the bundle, then an effective litz action is performed. Litz is most called for where layering cannot be avoided. Obviously turn and layer insulation has to be provided by something a little more predictable. This isn't hard to do. RL
From: life imitates life on 21 Feb 2010 22:44 On Sun, 21 Feb 2010 21:44:45 -0500, legg <legg(a)nospam.magma.ca> wrote: > >It doesn't really matter when, how, or why insulation between strands >is achieved and the voltage levels presented are extremely small, so >polymers are really overkill. It matters if it is not complete, and it touching other conductors along the way (and it will) causes problems. If not detrimental parasitics, in fact.
From: JosephKK on 22 Feb 2010 01:22
On Sat, 20 Feb 2010 12:04:21 -0600, Tim Wescott <tim(a)seemywebsite.com> wrote: >On Sat, 20 Feb 2010 05:38:23 -0800, dcaster(a)krl.org wrote: > >> On Feb 20, 5:47 am, life imitates life >> <pastic...(a)thebarattheendoftheuniverse.org> wrote: >>> On Fri, 19 Feb 2010 16:58:13 -0600, Tim Wescott <t...(a)seemywebsite.com> >>> wrote: >>> >>> >>> >>> >On Fri, 19 Feb 2010 16:18:49 -0600, Tim Williams wrote: >>> >>> >> "George Herold" <ggher...(a)gmail.com> wrote in message >>> >>news:550831a9-5935-4e3d-b37e- >c664ebd9d752(a)o3g2000yqb.googlegroups.com... >>> >>> We get Litz wire from MWS but nothing that big. If you don't need >>> >>> that much have you thought of 'rolling your own'? >>> >>> >> 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. >>> >>> >> Tim >>> >>> >Isn't there some magic braiding pattern for Litz wire? >>> >>> 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. >> >> No again. The wire strands have to be segregated and also braided so >> that some of the time a strand is on the outside of the bundle and >> sometimes on the inside of the bundle. See attached from Wiki. >> >> Litz wire uses some different tricks. Instead of using one big >> conductor, it uses lots of little conductors (strands) in parallel >> (forming a bundle). Each little conductor is less than a skin-depth, so >> an individual strand does not suffer an appreciable skin effect loss. >> However, that is not the complete story. The strands must be insulated >> from each other -- otherwise all the wires in the bundle would short >> together, look like a single large wire, and still have skin effect >> problems. Furthermore, the strands cannot occupy the same radial >> position in the bundle: the electromagnetic effects that cause the skin >> effect would still disrupt conduction. The bundle is constructed so the >> individual strands are on the outside of the bundle (and see low >> resistance) for a time, but also reside in the interior of the bundle >> (where the EM field changes are the strongest and the resistance is >> higher). If each strand sees about the same average resistance, then >> each strand will contribute equally to the conduction of the entire >> cable. > >Why, then, does it work to make up multi-strand wire bundles for SMPS >service where the wires are just lightly twisted into a bundle? Are >these getting one part of the way there, but not all? > >I had heard about the Litz wire 'gotta be a magic braid pattern', but >then I've seen all these SMPS transformers that just have almost-parallel >strands. It is not braided in the sense that hair is braided, it is twisted in increasing levels much like rope is. Say 3 strands twisted, in groups of 7, in supergroups of 3, in hypergroups of 7. Though this clearly would not be optimal. |