Litz wire

[pimpom]

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.

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.

 

[life imitates life]

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 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; 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.

 

[life imitates life]

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.

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.

 

[life imitates life]

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.

 

[life imitates life]

Yup. He's AlwaysWrong.

John

You're a goddamned retard, Larkin.

 

[life imitates life]

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.

 

[life imitates life]

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

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

 

[amdx]

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

 

[amdx]

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.

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

 

[amdx]

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

 

[life imitates life]

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
Your words above:

Tells me that John is full of shit, and that it was an agreement. Sure,
woven is required to be called true litz and be sold as such, but all the
configurations yield the effect, and as you perfectly stated, there is
good better and best.

Then, there is retarded, like Larkin.

I do not need to re-read anything.

 

[life imitates life]

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.

 

[life imitates life]

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.

 

[amdx]

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

 

[amdx]

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

 

[life imitates life]

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.

 

[life imitates life]

Scientific Wire Company:

http://wires.co.uk/

Leon

Half a kilo at over $80 fucking dollars? You guys are fucking nuts!

 

[legg]

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

 

[life imitates life]

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.

 

[life imitates life]

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.

Flat strip conductors negate skin effect in a similar manner as that of
a Litz wire configuration. The main problem with using it as wire is the
amount of space it takes up on a bobbin per turn. That makes it only
practical used as a hook-up link, or inter-node connection link between
points in a chassis.