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Hi there,

dows anybody have an idea for modelling a inductance with a permeability in dependency of frequency ??

I could not find anything in the messages ?!

Herbert

--- In LTspice@..., "Herbert" <afu@...> wrote:

Hi there,

dows anybody have an idea for modelling a inductance with a permeability in dependency of frequency ??

I could not find anything in the messages ?!

Herbert

Herbert,

I'd like to help you, but I don't understand your question. What do you want to know?

Rick

Hi Herbert


On 07/09/2013 12:45 AM, sawreyrw wrote:

dows anybody have an idea for modelling a inductance with a
permeability in dependency of frequency ??

A simple model would be an inductor in parallel with a resistor.

Most ferrous cores behave well up to a cross over frequency at which
the perm drops and they become very lossy.
The loss dominates above that freq and
the inductor looks pretty much like a resistor that
is flat with freq.



--


AC2CL

I do not think there is any thrill that
can go through the human heart like that felt by the inventor as
he sees some creation of the brain unfolding to success...
Such emotions make a man forget food, sleep, friends, love, everything.

- Nikola Tesla

I sometimes use a 'linear' representation of inductors to speed analyses.

Try a ladder network of linear inductors and resistors.

Just like in fitlering, you have to change the first and last components, sometimes the middle - think in terms of Tchebyschev(sp?) coefficients and you'll get the picture

*IF* you do that, it only takes somethinge like 5 to 7 terms (note the odd numbers) to pretty accurately match the performance of chip ferrite beads. As you know, chip ferrite beads start out a little inductive and then turn resistive, but as the impedance goes higher with increasing frequency the impedance angle seems to maintain the same angle, almost like eddy current losses.

The point is, using the array form of entering values and with a little bit of thinking; you can create subckts that match spec within about 1-5% over the spectrum, yet use LINEAR components - speeding up analyses to way faster than using the LaPlace equation form. which is the usual models given for these chips.



--- alzie@... wrote:

From: alzie <alzie@...>
To: LTspice@...
Subject: Re: [LTspice] Re: inductance with a permeability in dependency of frequency
Date: Tue, 09 Jul 2013 09:48:53 -0400

--- In LTspice@..., "sawreyrw" <sawreyrw@...> wrote:

--- In LTspice@..., "Herbert" <afu@> wrote:

Hi there,

dows anybody have an idea for modelling a inductance with a permeability in dependency of frequency ??

I could not find anything in the messages ?!

Herbert

Herbert,

I'd like to help you, but I don't understand your question. What do you want to know?

Rick

The permeability of some magnetic core materials is highly frequency-dependent - a good example is the amorphous materials marketed as parts for common-mode chokes.

At common test frequencies, these may measure ten to 100 times their effective inductance when applied in the narrow-band conducted emissions frequency range (100KHz-1MHz), where the impedance is most critical.

RL

Hi Alzie and aall the others which answered,

Alzie is nearly right with the way of explanation what I have seen, but
it is not possible to describe the behaviour by S?ICE just with a
parallel resistor.
On that page under B you will
find a real measured Z-Plot in vetorial notation ( with the phase on the
right side ) and the initial measurement of inductivity of 20uH. The
core is lossy in the range of the plot ( Amidon Mat 43) and the model
with jus the parallel resistance does NOT do enough or right. So my idea
was to define the permeability in its complex form and give a table of
values or artificaly evaluated polynom with permeabilty factors over
frequency.

Is it possible to give LTSPICE a value by a formula expression based on
a table ( interpolation???) ?

Thanks in advance

Herbert


Am 09.07.2013 14:48, schrieb alzie:

Hi Herbert

On 07/09/2013 12:45 AM, sawreyrw wrote:

dows anybody have an idea for modelling a inductance with a
permeability in dependency of frequency ??

A simple model would be an inductor in parallel with a resistor.

Most ferrous cores behave well up to a cross over frequency at which
the perm drops and they become very lossy.
The loss dominates above that freq and
the inductor looks pretty much like a resistor that
is flat with freq.

--

AC2CL

I do not think there is any thrill that
can go through the human heart like that felt by the inventor as
he sees some creation of the brain unfolding to success...
Such emotions make a man forget food, sleep, friends, love, everything.

- Nikola Tesla

[Non-text portions of this message have been removed]

Herbert (<afu@...>) wrote:

Is it possible to give LTSPICE a value by a formula expression based on

a table ( interpolation???) ?

Yes you can. But the problem is that it tends to work well in .AC analysis
but not in .TRAN analysis.

Also, many inductive devices with iron-based cores are nonlinear, which
makes them difficult (impossible) to quantify in the frequency domain alone.

Andy

In message <krbus2+ba2e@...>, dated Sun, 7 Jul 2013, Herbert <afu@...> writes:

dows anybody have an idea for modelling a inductance with a permeability in dependency of frequency ??

I want to go right back to the beginning. Because you gave very little information, people have assumed various things and that can make the whole thing complex and confusing.

First of all, what frequency range are we in, and what is the material whose permeability depends on frequency? Secondly, is this material significantly lossy in that frequency range or not?

For example, if you are looking at nickel-iron at audio frequencies, the losses are secondary, but if you are looking at ferrites at radio frequencies, then whether the losses are significant or not depends on which grade of ferrite you are looking at.

If the losses are NOT significant, then why bother with permeability? The inductance is proportional to it, so you can just use a table of inductance against frequency.

If the losses ARE significant, you CAN model as L and R parallel but both need a table of values against frequency.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Why is the stapler always empty just when you want it?

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Hi Andy,

as the game plays in the RF ham area, the AC view will be the right way !

I will try to find out, how it will work with the a table .

Thanks

Herbert

Am 14.07.2013 18:08, schrieb Andy:

--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:

Herbert (<afu@...>) wrote:

Is it possible to give LTSPICE a value by a formula expression based on

a table ( interpolation???) ?

Yes you can. But the problem is that it tends to work well in .AC analysis
but not in .TRAN analysis.

Also, many inductive devices with iron-based cores are nonlinear, which
makes them difficult (impossible) to quantify in the frequency domain alone.

Andy

Andy,

Nonlinear inductor work fine in the frequency domain. The first thing LTspice does for an .AC analysis is to find the DC operating point. Then any nonlinear devices are linearized at their operating point. .AC analysis, by definition, is a small signal linear analysis and it does not deal with nonlinear devices other than noted above.

Rick

--- In LTspice@..., John Woodgate <jmw@...> wrote:

In message <krbus2+ba2e@...>, dated Sun, 7 Jul 2013, Herbert
<afu@...> writes:

dows anybody have an idea for modelling a inductance with a
permeability in dependency of frequency ??

I want to go right back to the beginning. Because you gave very little
information, people have assumed various things and that can make the
whole thing complex and confusing.

First of all, what frequency range are we in, and what is the material
whose permeability depends on frequency? Secondly, is this material
significantly lossy in that frequency range or not?

For example, if you are looking at nickel-iron at audio frequencies, the
losses are secondary, but if you are looking at ferrites at radio
frequencies, then whether the losses are significant or not depends on
which grade of ferrite you are looking at.

If the losses are NOT significant, then why bother with permeability?
The inductance is proportional to it, so you can just use a table of
inductance against frequency.

If the losses ARE significant, you CAN model as L and R parallel but
both need a table of values against frequency.

Here's an example of a material exhibiting reduced permeability with frequency.



RL

--- In LTspice@..., legg@... wrote:

Here's an example of a material exhibiting reduced permeability with frequency.



RL

RL,

The link doesn't show anything about permeability vs. frequency.

Rick

--- In LTspice@..., "sawreyrw" <sawreyrw@...> wrote:

--- In LTspice@..., legg@ wrote:

Here's an example of a material exhibiting reduced permeability with frequency.



RL

The link doesn't show anything about permeability vs. frequency.

Rick

Material permeability is directly related to inductance of the sample, if only the frequency changes in the test.

RL

--- In LTspice@..., legg@... wrote:

--- In LTspice@..., "sawreyrw" <sawreyrw@> wrote:

--- In LTspice@..., legg@ wrote:

Here's an example of a material exhibiting reduced permeability with frequency.



RL

The link doesn't show anything about permeability vs. frequency.

Rick

Material permeability is directly related to inductance of the sample, if only the frequency changes in the test.

RL

RL,

I understand that, but there is no function of frequency shown at that link. If you don't think that is the case, double check it.

Rick

--- In LTspice@..., "sawreyrw" <sawreyrw@...> wrote:

I understand that, but there is no function of frequency shown at that link. If you don't think that is the case, double check it.

Rick

My mistake. Here's the web page and correct link:





Other related stuff there.

RL