FEA modelling of Litz wire

Anyone done FEA modelling of power magnetics incorporating litz wire?

Creating a physical model of the individual strands in a 3D winding looks a little challenging..

Reply to
Spehro Pefhany
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They use piece-wise linear analysis and develop physical models for litz wire. There's a matlab app as well, that might be useful.

FEA modeling of mixed materials has always looked like a head-ache to me. Takes a while to figure out that the CAD package can't do it, too.

RL

Reply to
legg

It's probably (definitely!) easier to breadboard.

John

Reply to
John Larkin

The cores are custom ferrite shapes- iterations are a bit slow and a bit expensive.

Reply to
Spehro Pefhany

They already exist, or are you forced to specify a new shape?

Never had much trouble finding core suitable core shapes, but never had much luck convincing mfrs to produce them in 'outside of the application' material. Complex shapes can also be prototyped from simpler structures.

FEA modeling with sheet/strands should tell you a lot about non-litz window fills - at least enough to know whether litz is potentially justified. Is this just a layering issue or a predictably troublesome core shape?

RL

Reply to
legg

It's all special/custom, but at least standard materials.

It's amazing (to me) what can be done when unit cost is not very important.

I'm hoping we'll be close enough, then just do an a/b comparison with the litz in a prototype.

Reply to
Spehro Pefhany

Dremel?

John

Reply to
John Larkin

CNC

Reply to
Spehro Pefhany

But they know what they want........

Meaning the sky's the limit, or that they can make anything needed, for peanuts, in volume?

Reply to
legg

Sure, it should work reliably. ;-)

Meaning, if I don't care too much about unit cost (unfamiliar concept), they can make whatever I can imagine (almost).

Reply to
Spehro Pefhany

Well, then. I would advise you to do a simple optimum volts per turn at frequency sweep, based on the power loss budget, before fiddling with winding structures. For any isolated topology with leakage limitations to power transfer duty cycle, there will be an optimum frequency range for the core volume, or an optimum volume range for a spot frequency.

Ferrite core designers seem to have forgotten that most parts, nowadays, are fixed with a close-to-unity turns, resulting in a situation that does not permit physical interpolation of core loss data in increments of less than 1/2 order of magnitude in a regulated system.

RL

Reply to
legg

What's the best way to deal with a non-negotiable large amount of leakage inductance?

Reply to
Spehro Pefhany

Either resonant, or clamped recovery, preferably with recovery directly into the intended load.

It's not non-negotiable if you have control over the magnetic structure.

RL

Reply to
legg

I wouldn't touch that with a Ten Foot Pole. But I know a 5' 8" Hungarian who seems to be a pretty astute magnetics designer -- send me email if you're interested, and I'll send you his contact info.

--
Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

5' 8" is the perfect size for a human male.

John

Reply to
John Larkin

:
a

Magnetic shield further away?

George H.

Reply to
George Herold

I was gonna ask if he knew any ten foot Poles.

George H.

Reply to
George Herold

What FEA are you trying to resolve? Thermals? Mechanical stresses?

Or are you talking about electrical characterization of such items? THAT is NOT FEA.

Reply to
TheGlimmerMan

Truly, the only way to properly "select" an inductor or transformer is to experiment and characterize in the lab. I spent two years going over a power supply for the med industry where a single turn more OR a single turn less than the final number made a huge difference.. THEN simply using Litz improved it further.

Rather than trying to model Litz, one should use standard models for ordinary transformation. THEN use different Litz configurations and FIND the best one for that form factor xformer and operating frequency.

There will ALWAYS be an improvement. THAT is all one needs to count on. Put numbers to the standard, and KNOW that you will get better performance from the change to Litz (even simple bi or tri filar yields results). The inductor was the same way. The result is/was not merely better performance, but the unit ran down to a lower drop out point on the line side as a result as well. So it would work all the way down to

3.5 Volts when it used to drop out at 6 Volts.
Reply to
TheGlimmerMan

Once you have had one batch made, subsequent batches cost far less.

Reply to
TheGlimmerMan

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