Relative permeabilities in steel datasheets

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The discussion centers on confusion regarding the use of J instead of B in the magnetization curves of electrical steel datasheets, specifically for the Isovac 330-35A. Participants note that J appears to represent magnetic polarization rather than magnetic flux density, which is typically denoted by B. There is a discrepancy in calculated relative permeability values, with one user obtaining a maximum of 7.07e3 instead of the expected 8.23e3. The conversation suggests that the datasheet might be using different values for permeability and magnetic flux density, possibly due to AC versus DC considerations. Clarification from the vendor is recommended to resolve these inconsistencies.
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How to interpret the data in an electric steel datasheet?
Hello,
I have a question regarding BH-curves and relative permeabilities from electrical steel datasheets. When e.g. looking at the datasheet from the isovac 330-35A there is the data for the J/H-curve. I calculated B=mu_0*H + J and mu_r=B/(mu_0*H). When evaluating this calculation pointwise with the the data from the table, I don't get the same mu_r/J curve as shown in the datasheet. My maximum mu_r is 7.07e3 instead of 8.23e3. What am I not considering?
 
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(2nd edit ... hmmm ... on second thoughts I agree that doesn't look quite right in the data sheet)
 
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I took a preliminary look at this specification sheet. The first thing that confuses me is that it seems to use the "J/H magnetization curve" instead of the "B/H magnetization curve". People usually use B to represent the magnetic flux density, but in this specification use J to represent.
 
alan123hk said:
I took a preliminary look at this specification sheet. The first thing that confuses me is that it seems to use the "J/H magnetization curve" instead of the "B/H magnetization curve". People usually use B to represent the magnetic flux density, but in this specification use J to represent.
It's giving AC values. B is usually a letter for DC flux. I assume they are using J to denote it is an AC flux.

I originally looked at that thinking they'd plotted initial (DC) permeability on the first graph (and labelled it wrong) and assumed the OP was talking about that (which is ALSO a difference with the graphs). But the data itself in that table doesn't calculate through.

If they have in mind that there is some sort of adjustment for AC then I am not sure what that is. They seem to have used a value for uo of about 1.1e-6 instead of 1.25e-6 to arrive at their permeability values. I don't know maybe there is some sort of adjustment for this sort of AC calculation but I have never heard of it.

At this point I'd be contacting the vendors for a clarification.
 
Steradiant said:
I calculated B=mu_0*H + J and mu_r=B/(mu_0*H)
I can understand that ## ~u_r = \frac B {u_0H} ##, but I don't quite understand why ##~~B=u_0H+J##.

Do you think ##J## is related to the vector current density and magnetization vector ##M## of ferromagnetic materials ? But according to the specification, the unit of ##J## is mt (millitesla), so it should represent the magnetic flux density.

Steradiant said:
My maximum mu_r is 7.07e3 instead of 8.23e3. What am I not considering?
Could you please elaborate on how you calculated this result ?
 
In table on page 2 they list the magnetic polarization in Tesla. Therefore I assumed, that J in the Table is the magnetic polarization (https://en.wikipedia.org/wiki/Magnetization#Magnetic_polarization). As far as I know it's pretty common to use the magnetic polarization instead of the magnetic flux density in the material characterization.

mu_r = 1+J/(mu_0*H) = 1+0.8/(mu_0*90) = 7074.55
 
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