Re: BH data

["mikejhutch" <mhutchings@xxxxxxxxxxxxxxxxxxxxxx>]

--- In femm@xxxx, Keith Gregory <k.gregory@xxxx> 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.


> 
> >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.


> 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.


Mike