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# Re: [femm] Re: BH data

- To: femm@yahoogroups.com
- Subject: Re: [femm] Re: BH data
- From: Muchlis Achmad <machmad@yahoo.com>
- Date: Fri, 25 Oct 2002 16:57:42 -0700 (PDT)
- In-reply-to: <5.1.0.14.0.20021025082557.01d63008@staff-mailin.lboro.ac.uk>

I am just wondering how do you differentiate the effect of self inductance vs. eddy current in FEMM? At 10 - 100Hz, I would think that the self inductance is the one to consider.

Keith Gregory <k.gregory@lboro.ac.uk> wrote:

> `At 15:31 24/10/2002 +0000, you wrote:
> >--- In femm@y..., Keith Gregory <k.gregory@l...> wrote:
> > > 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.
> >
> >
> >A basic model LVDT model using mumetal core at even 100 Hz shows
> >pronouned skin effect. At 5kHz there is a danger of saturation near
> >the material surface at normal drive levels.
> The 5kHz doesn't surprise me but the 100Hz does, although mumetal is
> different to the materials I would normally work with.
> > >
> > > >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?
> >
> >
> >I hope to use LF ac to cycle the jumps and give larger noise output.
> >Literature suggests that Barkhausen noise can indicate heat treatment
> >and internal stresses, inter alia; as properties of cores are
> >affected by handling stresses I believe BN can provide an insightful
> >tool into known quality issues.
> I could see that, since Barkhausen noise has been attributed to sudden
> domain wall movement and some people say that it is impurities and voids in
> the material that make the walls stick, the amount of noise could give an
> indication of the material structure and quality.
> It would be interesting to see if it really is "noise" or it has some
> pattern during repeated cycles.
> > > In addition, if my memory serves aren't there several different
> >Radiomental
> > > alloys differentiated by a number such as Radiometal 36?
> >
> >
> >Yes. The 36 refers to % nickel in the alloy. Varoius types give
> >different permeability / resistivity / cost materials for different
> >applications.
> Keith.
> `
> `Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.`

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