Litz wire

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 re-examination

"life imitates life" wrote in message news: snipped-for-privacy@4ax.com...

No need to do trial and error, Here's a table that gives recommended gauge with regard to frequency. See Table B.

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

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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

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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.

=20 Dan

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'.

RL

Yup. He's AlwaysWrong.

John

snipped-for-privacy@o3g2000yqb.googlegroups.com...

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's just a matter of good, better, and best. Best would be properly braided* and would have the least AC resistance. Mike

Insulated strands have much lower eddy current loss than an equivalent big fat wire. Maybe less skin loss too.

As I understand it, if you do the multi-strand thing, the inner conductors can conduct less at high frequencies, for some magnetic reason. Litz braiding gives each conductor equal exposure. Loss goes as I^2, so it's good to keep the currents balanced.

But the simple multi-strand thing has higher copper density and shorter path length than braided Litz, and low eddy-current loss, so it's usually good enough. Copper loss will balance the currents some, too. It's also easier to use than solid #8 or true Litz.

Litz was really good for super-high Q inductors, like pot cores for low-frequency passive filters. That's a dying art, given active filters.

I've seen really sloppy multistrand windings in SMPS inductors, not even twisted, just sort of all over the place. That may result in Litz-like current equilization.

John

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 rec.radio.amateur.antenna 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. Mike

One reason for using multi-strand wire even at mains frequency is that it utilizes winding space more efficiently than a single wire of the same cross-sectional area. Another reason is that multi-strand is easier to handle because of its greater flexibility. I've experienced both effects in practice.

I can't speak authoritatively about the use of simple-bundled wire in SMPS transformers, but my guess is that it's a compromise of cost, availability and effectiveness. Individually insulated strands bundled in parallel should exhibit less skin effect than a large single wire, though perhaps not as effectively as specially braided true Litz wire. And at least some manufacturers are probably using it without investigating the effectiveness.

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.

It is indeed ideal, but not absolutely required. If you bundle does not conform to the pristine definition, it does not preclude it from exhibiting the effect, nor does it preclude you from calling it Litz wire.

You're a goddamned retard, Larkin.

As we all know, you're AlwaysWrong.

John

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 obtained huge improvements, and the use of pro grade "real" litz would have only improved it a slight bit more.

Please tell this to the Larkin retard that attacked me after your last post.

Please reread my last response to you, 2-20 7:33am that was a rebuttal (attack) on your 2-20 12:06am post. I see someone used the term woven, maybe a better term than braided? Mike

"life imitates life" wrote in message news: snipped-for-privacy@4ax.com...

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

Stop being nice to me! Mike :-)