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Re: [femm] Re: BH data

Mike,

I think you would find that static finite elements models with single valued magnetization characteristics would give pretty good approximations of field distribution and winding inductances in the 50-60Hz types of applications where the materials are laminated. Although calculating inductances in saturated conditions is complicated. Loss calculations even at 50 or 60 Hz are not as straightforward. Operating in Khz I really have no idea how good results would be.

Manufacturers' mag curves are, I think, measured under DC conditions (if anyone wants to contradict me here please do, it would be useful to know).

The d.c. hysteresis loops cited are from manufacturers data (Telcon
Metals, Crawley, long since defunct). Presumably these would be
compiled from slow changes at a few Hz max; if not then a.c. effects
may come into play.

Manufacturers' mag curves are, I think, measured under DC conditions (if anyone wants to contradict me here please do, it would be useful to know).

I am currently interested in trying to observe Barkhausen noise for
NiFe materials. I expect to use up to about 100 Hz field for this, and
believe that the spectrum of the noise will contain much information,
if it can be unravelled; early days yet. Comments are very welcome

The classic demonstration of Barkhausen jumps is done with "DC" magnetization, usually with a permanent magnet. I have a vague memory of a paper describing a different way which can produce noise displays on an oscilloscope. I'm not sure what information it would contain though, what had you got in mind?

In addition, if my memory serves aren't there several different Radiomental alloys differentiated by a number such as Radiometal 36?

Keith.

In femm@xxxx, Keith Gregory <k.gregory@xxxx> wrote:
> Michael,
>
> Could I ask what you mean by low frequency?
>
> Keith.
>
> At 15:30 21/10/2002 +0100, you wrote:
>
> >Hi David (Meeker) and others,
> >
> >I am trying to include Radiometal in the materials library. I have
the
> >manufacturers data for d.c. induction but it is in the form of an
initial
> >magnetisation curve. This is unlike the mumetal and supermalloy
materials
> >in the femm library, which show a high initial slope /
permeability,
> >declining steadily as saturation is approached. These plots ignore
hysteresis.
> >
> >I am tempted to input data from the radiometal d.c. hysteresis
loops which
> >I also have, shifted to pass through the origin. At least then the
plot
> >shape is correct. Is this likely to give acceptable results for
modelling
> >of low frequency fields and inductances?
> >
> >Perhaps the included BH curves are similarly derived. I feel it
will be
> >better to do this than use a description with an initially
increasing
> >permeability with H.
> >
> >BTW thank you for an excellent free tool, and all the inputs to an
> >interesting discussion group.
> >
> >Michael J Hutchings







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