Type 43 material for common-mode choke

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The article here says type 43 NiZn ferrite's resistive impedance exceeds
it's reactance at about 2MHz

<https://www.nutsvolts.com/magazine/article/July2015_HamWorkbench#:~:text=Type%2043%20is%20one%20such,video%20cables%20use%20this%20mix .>

but I think that's a misprint, looks more like 15MHz:

<
https://www.nutsvolts.com/uploads/wygwam/NV_0715_Silver_Figure01.jpg


The data-sheet is here:

<https://www.fair-rite.com/43-material-data-sheet/

I have a bunch of FT37-43s ferrite toroids on hand and I need a 100uH  
common-mode choke for about 3 MHz, the calculator says about 30 turns  
should give me that but I'm unclear if this is an appropriate material

Re: Type 43 material for common-mode choke

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That's a 5943000201 in the Fair-Rite catalog. Al = 375nH/n^0.5.

You'd only need 16 turns x2 to get a 2x100uH common mode choke.

It's the right material for the application.

RL

Re: Type 43 material for common-mode choke
On 9/24/2020 11:17 PM, legg wrote:
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Yes you're right, 16, thank you. Nice

Re: Type 43 material for common-mode choke
legg wrote:
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375nH/n^2

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Yes.

Jeroen Belleman

Re: Type 43 material for common-mode choke
On Fri, 25 Sep 2020 09:31:40 +0200, Jeroen Belleman

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Too many turns can eventually give diminishing returns due to too much
intra-winding capacitance.



Re: Type 43 material for common-mode choke
On Saturday, September 26, 2020 at 3:20:43 PM UTC+10, boB wrote:
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You can work that out.  Sixteen turns on a toroid sounds like a single layer winding, where the parallel capacitance tend to be around 1pF, which would make the coil parallel resonant at about 8MHz (very roughly).

As soon as you start stacking up layers of windings, life gets more difficult and you have to starting thinking about partitioning the winding into successive multilayer chunks, where there isn't a lot of voltage difference within any one chunk.

--  
Bill Sloman, Sydney

Re: Type 43 material for common-mode choke
On 26/09/2020 06:36, Bill Sloman wrote:
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Very roughly indeed, an octave out - I make 1pF 100uH resonant at 16MHz


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piglet



Re: Type 43 material for common-mode choke
Piglet wrote:

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I would say an octave is good enough for a SWAG. Even a decade would  
pass in most of the cases.

    Best regards, Piotr

Re: Type 43 material for common-mode choke
On 26/09/2020 09:12, Piotr Wyderski wrote:
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You are right when some information is missing but in this case all the  
data was available to calculate better.

piglet


Re: Type 43 material for common-mode choke
On Saturday, September 26, 2020 at 6:48:34 PM UTC+10, piglet wrote:
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I agree with piglet. I'm not in the least pleased with myself.

--  
Bill Sloman, Sydney

Re: Type 43 material for common-mode choke
On Saturday, September 26, 2020 at 6:00:29 PM UTC+10, piglet wrote:
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Oops. I wasn't reading carefully enough. I got quite the wrong inductance, and seem to have plugged in the wrong capacitance too.

Repeating the calculation gives me 15.9MHz - which certainly isn't worth reporting as anything different from 16MHz.

A common mode choke is going to use a bifilar winding, which is to say a length of twisted pair, which has a very well-defined interwinding capacitance, which I'm no longer game to try to work out.  

Thanks for the correction .

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--  
Bill Sloman, Sydney

Re: Type 43 material for common-mode choke

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There is no such thing as material 'Q'.

When you assume subjective properties in  
magnetics, you make a fool of you and me.

RL

Re: Type 43 material for common-mode choke
On 9/26/2020 10:33 AM, legg wrote:
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I think the crossing point is where the resistance is equal to the  
reactance. No?

If so, then the Q at that point is 1. No?

Re: Type 43 material for common-mode choke
wrote:

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The material itself doesn't have reactance. It does  
have a bulk resistivity, but that isn't directly  
related to core loss effects, though lossy materials  
can often be identified by their low bulk resistance.

"It was my understanding the that the point where u' and u"  
cross on apermeability curve is where the material Q = 1."

- Refers to a graph constructed using measurements performed  
on a predifined core shape and turns count, as comparative  
reference information for the core material in question.
The graphical contents would change with a different core  
shape or winding configuration - shifting this specific 'Q'  
point, without altering the material composition of the core.

Another common graph is for the single-turn bead, which  
attempts to reduce winding effects on measurement of the  
loss characteristic. Each bead size and shape will still  
have its own curves, without alteration in the core  
material type.

Anyone can stipulate that a Q factor exists for the relation  
between any two measurable quantities. providing that its  
definition is presented within the scope of the work.

In a non-resonant circuit, the term has little meaning,  
as losses in the core are (non-linearly) dependent on the  
amplitude of the peak flux excursion, and many other  
inter-related physical factors of the core and winding.

RL




  

Re: Type 43 material for common-mode choke

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A lot of instruments to measure inductors and capacitors report Q, by
which they mean the ratio of reactance divided by resistance at the
chosen test frequency, well away from resonance.

Joe Gwinn

Re: Type 43 material for common-mode choke
wrote:

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As long as they tell you what they're talking about, then  
they can call it anything they want.

Q is not a characteristic of the core material.

RL

Re: Type 43 material for common-mode choke
On 9/26/2020 5:16 PM, legg wrote:
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Perhaps not. But as soon as you put a wire through the hole it has Q at  
some point. What good is the core if it not used?

Re: Type 43 material for common-mode choke
wrote:

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Graphs ARE available for parts under that specific condition,
and for that use.

The OP, however is refering to a graph for 43 matl, and is only  
applicable to a 17mmOD /10mmID / 6mmH test speciment with an  
unknown number of turna. Fairite, the mfr of 43 matl, doesn't  
even bother to offer this part size for sale. It is a lab test  
specimen.  

The size of the test specimen can vary from one matl data sheet  
to the next. None are necessarily commercially-sized parts,  
though some manufacturers do use a recognizable part number.

For core material there IS a 'relative loss factor' which is  
specified as a maximum limit value at a test frequency.  
There ARE graphs for that - check Magnetics Inc matl data.  

RL

Re: Type 43 material for common-mode choke

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Many LCR meters report Q as a ratio of reactance divided by resistance.  

For example, the Agilent / Keysight U1733C 100Hz/120Hz/1kHz/10kHz/100kHz  
Handheld LCR Meter:

https://literature.cdn.keysight.com/litweb/pdf/U1731-90076.pdf

Re: Type 43 material for common-mode choke

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 . . and I'm sure they're very useful in measuring actual components.

If you care to reconstruct the test sample, you might even be able to  
replot the graph in the 43 matl's data sheet, given sufficient test  
frequencies.

Enough of this foolery.

RL


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