Help converting Ferrite loss terms

Hi Guys, I have two different Ferrite materials. Each shows loss in different ways and terms.

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This page has the loss as 1000mW/CM^3 with a flux density of 100mT at 100kHz.

What is the loss of this material at 100kHz with a flux density of 100mT? It's in graph form with different terms.

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I read it as 200kW/M^3 with a flux density of 100mT at 100kHz.

My problem is mW/cm^3 vs kW/M^3.

I think I just got it. mW to kW is a factor of 1,000,000 cm^3 to M^3 is a factor of 1,000,000

Making the 77110-A7 material 5 times more lossy. I thought this was a better material regarding loss.

I feel I missed something.

Help, Mikek

Reply to
amdx
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Den tirsdag den 24. februar 2015 kl. 23.57.29 UTC+1 skrev amdx:

The magic of SI units ;)

-Lasse

Reply to
Lasse Langwadt Christensen

Darn, I didn't want to be right, I wanted the Kool Mu material to be less lossy.

Thanks, Mikek

Reply to
amdx

It ain't. Powdered metals rarely come out ahead by losses, sadly.

Also, 3C81 is an old ferrite, 3C90-94 are newer. Difference is, slightly improved. Or if you're really concerned with losses (and frequency), find something 3F3 or similar.

I forget what the TDK/EPCOS crosses are to these materials; roughly speaking, Fair-Rite #77 and Magnetics #P are similar to 3C80 or thereabouts (I don't know them in great enough detail to say which 3C80-90 series mix is closest), and 3F3 is... kinda like Fair-Rite #43 (yes, the ferrite beads stuff), but it's a MnZn rather than NiZn ferrite, so that's kind of a stretch in a number of dimensions (the #43 is probably lower loss for most typical power switching uses, and will certainly have lower Bsat and higher cost due to the Ni content).

Tim

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Tim Williams

btw. google understands many units, e.g. if you type "mW/cm^3 / kW/M^3" into google it'll tell you "= 1"

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-Lasse

Reply to
Lasse Langwadt Christensen

Ya, we moved to 3F3 after 3C81 about 18 or 20 years ago. I bought out all the stock when the company folded. We tested the Kool mu at 660kHz and as I recall it ran cooler than the 3C81, so I don't know if the flux density was lower in our use or what. Just playing with AMBC ferrite antenna and using a large stack of potcores as a rod (really three).

Here's the 3 ferrite rods, (9" x 2-1/4")

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THis is with wire and cap.

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Got the idea to play, from the FSL antenna articles of late. The 3C81 material is not right for AMBC but I am getting much enhanced signals. Anyone think they know a better form for the ferrite to improve reception? (signal capture) BTW, you just put and AM radio near the resonated ferrite for enhanced signal. Mikek

Reply to
amdx

AT 100kHz.

To REALLY compare, overlay the loss, frequency, and at what B-Field. and the permeability etc. You may find that the one materil has better perfomance depending on operating point, or have a genereal voerall flatter response, etc

Sorry, I didn't, so don't know. But remember that if you use the ocre at

100kHz, there can be a lot of energy at 300kHz, 500kHz, etc. And often the 'uppoer' harmonics heat the core more during actual use.
Reply to
RobertMacy

I'm sure your aware the ferrite manufacturers do a poor job with giving out all the information. Ferroxcube shows permeability out to

8MHz and losses to 200kHz. We used it regularly at 660kHz and at over a 1.2 MHz a few times, for transformers and inductors., And then the next company does it a little different, making comparisons tricky.

I would like to see tham graph losses along the frequency spectrum that the core may be used at. I'm using then as an antenna for 540kHz to

1700kHz. So the 100kHz loss graph is about useless, except that I might infer, if it is more lossy at 100kHz it is probably more lossy at 1MHz. At this time, I'm just using them for radio signals, no concern about heat. Just thinking about keeping Q high.

I have about 16 large toroids made with Kool Mu and was going to add more ferrite to the antenna I posted pictures of. I could add a few more inches of capture area if I inserted the toroids, but I don't want to increase losses.

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Mikek

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Reply to
amdx

I answered before I saw your application.

Have you looked into amorphous metal?

being amorphous they have almost NO coercivity [1/100th], which translates to small losses, but being conductive the skin effect has to be watched translating to some losses. [approx 0.7 MS/m]

The samples of metglas come in metal sheets, rolled up into tubes. Sound familiar? that's around 25 microns to almost 100 microns thick sheets. Put 'shiney' side out, that's the side that is more amorphic than the 'dull' side. At 1MHs skin depth is ?? what 1-2 microns, you only want to use the most amorphic side.

I've measured relative permeability over one million, which is like a magnetic 'dead short'. From memory, a 4 inch diameter tube has some interesting properties in free space.

femm 4.2 will show you whether better, or worse. just interesting.

Also, watch out for shattered material and/or 'paper' cuts. You can be dripping blood before you notice. and the organic? contamination in a cut makes it hurt like hell later. And, the stuff rusts at the drop of a hat, so keep any samples sealed.

There is a natural curvature across the sheet, short direction, I've never tried 'rolling' along the length, but you could conceivably make a 'rod' that's 2 inch diameter over 2-3 ft long. Or, spiral sheets(?) and get wider diameter with some incredible lengths. Air gap coupling is just that, air gap, so have to be carful. Might be best with parallel sheets, electricall isolated, making a 'rod' that's 1 foot in diameter, around 10 ft long. Just a 'hollow' tube core.

Did you find that last page of te ld Fairite catalog? Where they plot 'effecive' permeability versus length to diameter ratios and permeability?

Reply to
RobertMacy

I haven't, but it sounds interesting.

Back to my 40 year old thought, why do transformers work on single digit microvolt signals. But they do.

This guy says to optimize an FSL maximize L x D. Then goes on to give example as evidence.

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In emails with FSL builders it was said that only the outer surface of the FSL matters. Or said another way, flat bars don't waste as much material as rod. So the sheet material sounds good.

Where are you getting this material?

**************************************

It would be an interesting experiment, as you see on the optimization page I posted, They seem to be going for larger diameter vs length. But I don't know if that is because they don't want to stack rods end to end or if it is result dependent.

Again, don't know if Length or Diameter is the key, or is is just the combination. Also, does getting to long, mess up the null, which is important for eliminating an offending signal.

I didn't look, but I have seen it before, in the end, just put enough turns on to make about 240uH (AMBCB use) to resonate with a 360pf cap. This combo usually will tune the entire AM band. Then there is a contra wound coil that allows a bit smaller capacitor and gives a higher Q in the upper part of the band.

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Mikek PS. Where are you getting the Amorphous material?

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Reply to
amdx

Arrgh!

The first amorphous material I looked up has loss shown in "Watts per kilogram/Tesla" Not area, but weight!

And only show losses up to 100kHz.

Mikek

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Reply to
amdx

How do you suppose receiver input "transformers" work? A microvolt input on a coil will still produce some portion of that on a coupled coil. Are you asking if the core is in the way, or what?

Reply to
John S

That's was my starting point, receiver input transformers, a microvolt is enough to overcome the coercivity (I think that's the wrong term), a microvolt is enough to move the domains from one polarity to the other. (or some domains part way) I understand they work, it's just that they work over a 10 million, maybe even a 100 million range.

I've been over this before but it seems like there would be more info about it. And this is, the difference in permeability (AsubL) at 1 uV vs 100 volts. Converted to whatever current. I've never seen a paper on the special adjustments when winding radio input transformers. Maybe it's trivial. Back to the 4 times rule. (not again :-)

Anyway, I'd rather have input on the ferrite antenna and how to improve it. :-) Thanks, Mikek

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Reply to
amdx

Everyone does it differently, eh? :)

At least iron is 7 kg/L so it's not hard to convert. All amorphous magnetic alloys are iron, nickel or cobalt based, so they're pretty much not outside the 6.5-8 kg/L range.

Losses are essentially eddy current in nature. See the curve of this VAC common mode choke;

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(blue curve is datasheet, fine red curve is model)

It's probably reasonable to assume the diffusion region (Z ~ F^0.5) starts at the same impedance* for all materials (corresponding to the material resistivity, sheet thickness and skin depth), and continues until the capacitance between sheets dominates (or the winding capacitance, whichever comes first -- they act in parallel).

*Ah, but this is acting as a transformer above the core material. I don't know how many turns are on this part, probably around 12 if I had to guess. You need to know that to find the single turn equivalent resistivity. Impedance. Impedantivity?

Tim

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Reply to
Tim Williams

I've never heard of Impedantivity. Do you have a link to the definition?

Reply to
John S

Yes; my post, just then. English works that way. :^)

Point being, RLC due to the core should be expressed as Zcore / t^2. For most cases, this is the inductivity A_L. If you had a constant resistance core (very representative of powdered irons above eddy cutoff), it would be the resistivity (which is an already-claimed term, so this should be specified with an adjective).

Tim

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Reply to
Tim Williams

I don't understand. I thought I knew English and how to look up words I do not understand.

The only curves I have seen are plotted with u' and u'' which, when applied properly, provide R+jX of the core. Is this what you mean?

Reply to
John S

If you're looking in a book, you won't find it. Measure it. No one gives resistivity (maybe call it A_R?), at best you have your choice from u'/u'', |mu| vs. F (same thing, assuming the dispersion relation holds -- it should, as there's no reason for nonminimum phase BS in such a system), and losses (P vs. Bmax and F, in graph or generalized Steinmetz form).

In any case, that needs to be modified to account for air gap (if any), Ae and le. So, you can derive an estimate from those data, yes.

Depending on amplitude, frequency and geometry (namely, electrical width of the core), the mu'/mu'' graph and similar data aren't even applicable; strictly, they're only valid at the geometry (it should say what core size was measured, and on what equipment) and amplitude used. The difference can be quite strong for ferrites; most of which work out in the GHz (finally limiting on electron paramegnetic time constants), but which are limited by capacitance, skin effect (yes, even of ferrite) and so on to lower frequencies. A graphic example of this is the peak impedance frequency of a multilayer ferrite bead; it's lower in frequency, and taller in amplitude, for more turns/layers. Even though made of a material that apparently rolls off at only 10MHz -- for the 20mm toroid case, or whatever.

Ferrite losses are often quite different from resistive (i.e., an idealized Steinmetz of P ~ F^1 B^2), perhaps having more relative losses at lower signals due to low initial permeability, a sweet spot in the middle, and greatly exaggerated losses at high B (the exponent is often pushing 3), and worse into saturation.

Tim

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Tim Williams

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