Litz wire
in [Design]
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From: amdx on 20 Feb 2010 15:26 "life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in message news:igg0o59fq9ba46j5e5trvgnld48aaa8ljk(a)4ax.com... > On Sat, 20 Feb 2010 13:33:56 -0600, "amdx" <amdx(a)knology.net> wrote: > >> >>"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in >>message news:oob0o5puoec968jqcott9mnjftvbup9q0i(a)4ax.com... >>> On Sat, 20 Feb 2010 07:33:54 -0600, "amdx" <amdx(a)knology.net> wrote: >>> >>>> >>>>"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote >>>>in >>>>message news:sauun5t4ct7i1ule9dj0lsihmjv5u5ecvs(a)4ax.com... >>>>> On Fri, 19 Feb 2010 17:57:41 -0800, John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>>On Fri, 19 Feb 2010 13:21:36 -0600, "Tim Williams" >>>>>><tmoranwms(a)charter.net> wrote: >>>>>> >>>>>>>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. >>>>>>> >>>>>>>Tim >>>> >>>> >>>>> 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". >>>> >>>> No need to do trial and error, Here's a table that gives recommended >>>> gauge >>>>with regard to frequency. >>>>See Table B. >>>> http://www.litz-wire.com/technical.html >>>>Same thing in pdf. >>>>http://www.litz-wire.com/New%20PDFs/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; http://www.dartmouth.edu/~sullivan/litzwire/skin.html >>>>"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! >>>> Mike >>>> >>> >>> >>> Nice work there. Spot on. >>> >>> I wish the individual strand currents in these groups were all >>> equalized. As it stands there are a bunch of dolts claiming to be on >>> the >>> ball, but obviously a bit kinked. You seem not to number among them >>> most >>> times I ever noted. >> >> Stop being nice to me! >> Mike :-) >> > Look at the chronology of the replies. > > Since you sucked up to Johnny's horseshit, you really still possess > many of their flaws. You'd be best to jump off their retarded little > bandwagon. I feel better now. Thanks, Mike
From: Leon on 20 Feb 2010 15:50 On 19 Feb, 19:21, "Tim Williams" <tmoran...(a)charter.net> wrote: > 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.. > > Tim > > -- > Deep Friar: a very philosophical monk. > Website:http://webpages.charter.net/dawill/tmoranwms Scientific Wire Company: http://wires.co.uk/ Leon
From: life imitates life on 20 Feb 2010 17:02 On Sat, 20 Feb 2010 14:24:55 -0600, "amdx" <amdx(a)knology.net> wrote: > >"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in >message news:asf0o55ka49rk4f0s36tkrjmljidttukod(a)4ax.com... >> On Sat, 20 Feb 2010 13:31:54 -0600, "amdx" <amdx(a)knology.net> wrote: >> >>> >>>"life imitates life" <pasticcio(a)thebarattheendoftheuniverse.org> wrote in >>>message news:dlc0o5d79sckha2l6lqqa6090aba6eqkfd(a)4ax.com... >>>> 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? >>>> >>>> Yes. Depending on the gauge, woven will perform better, but ANY >>>> configuration that splits up the current flow into smaller diameter runs >>>> is going to yield some litz effect and will definitely be better than a >>>> single solid strand of equivalent gauge for both transformer operational >>>> efficiency, as well as current handling capacity. >>>>> >>>>>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. >>>> >>>> I obtained huge improvements, and the use of pro grade "real" litz >>>> would have only improved it a slight bit more. >>> >>> Can you quantify that? What frequency? What size wire? How many in the >>>bundle? >>>What was the original single wire design size? And what do you mean by >>>huge >>>improvements? >>>Is this a Q measurement or a reduction of heat. >>> Mike >>> >> >> When one is dealing with a five turn primary and makes fifty different >> transformers, all classed over time for their operational characteristics >> in the same front end, one eventually compiles huge data sets of said >> characteristics. >> >> A single, solid 18 ga primary was far less efficient than the final >> litz wire I ended up using. As I configured each ga and strand choice, I >> noted the gains and arrived at the optimal ga for the frequency I was >> running at. It matches the ga in a table mentioned by a respondent in >> this thread, though I was at a slightly larger ga. Imagine that. I >> probably could have made it run even better if I had continued into >> testing a few yet smaller strand choices. >> >> Regardless, the unit went from dropping out at just below 6 volts, which >> would not meet the spec, to running all the way down to below 3 volts. >> The designed source is a 9 volt battery. >> >> It also made the choke on the driver FET operate far better. It was 5 >> turns on a core not much bigger than a quarter inch in diameter. It took >> testing of several core types and sizes as well as turns count and wire >> choices. >> >> Yes, optimally, A Litz configuration has to have the strands arranged >> so that they do not remain in the center of the bundle, BUT the >> difference is not that great, especially on miniature transformers meant >> for low power switchers and the like. The fact that a solid core is no >> longer being used means the effect WILL occur, even if a given strand >> never makes it out to the edge of the bundle. > >What frequency? What size wire? How many in the >bundle? > Mike > We ran at about 57kHz, and found that to be an optimal frequency for the cores we were using and characteristics of the switching circuit design we were using. It ended up being the equivalent for 18 or 20 gauge, and was using both 36 and 43 gauge. I think I ended up using the 36, since I mentioned using a few gauges larger size than the table described for that frequency. I cannot remember the strand count, and do not feel like extrapolating it for you. I posted the formula already.
From: legg on 20 Feb 2010 23:55 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
From: George Herold on 21 Feb 2010 00:22
On Feb 20, 8:38 am, "dcas...(a)krl.org" <dcas...(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. > > Dan- Hide quoted text - > > - Show quoted text - Cool, Thanks Dan. I'd never thought of that. A bit OT, but I remember seeing a video of high current experiments done at the Magnet Lab, (then at MIT circa 1960's) Where they were using several ~2-3" wide strips of copper. |