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B-H curve for Soft Iron

Posted Jun 11, 2013, 6:32 p.m. EDT Low-Frequency Electromagnetics, RF & Microwave Engineering, Materials Version 4.2, Version 4.2a, Version 4.3a 6 Replies

Fadi Nazzal
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Hello there !

I am about to use (soft iron) as a core for a saturable device . I need to specify the H( knee) & B(sat) points, but the listed values of B & H in the BH curve seem to away different from what I've found in this link:

www.fieldp.com/magneticproperties.html

Could you help me in figuring out what is the problem !
6 Replies Last Post Apr 5, 2016, 2:29 p.m. EDT
Jens Krause
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Posted: 1 decade ago Jun 12, 2013, 2:37 a.m. EDT
Hello,

the webpage that your link points to has data of relative permeability, but the BH(or HB)-curves
in Comsol have the magnetic field strength. Is that was is different? I did not convert the that
to check.

Regards

Jens
Hello, the webpage that your link points to has data of relative permeability, but the BH(or HB)-curves in Comsol have the magnetic field strength. Is that was is different? I did not convert the that to check. Regards Jens
Fadi Nazzal
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Posted: 1 decade ago Jun 12, 2013, 8:03 a.m. EDT


That's right, but if you tried to convert, there will be a huge difference !.


Can anyone at least provide the H(knee) for Soft Iron?

Thanks Jens,
That's right, but if you tried to convert, there will be a huge difference !. Can anyone at least provide the H(knee) for Soft Iron? Thanks Jens,
Robert Koslover Certified Consultant
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Posted: 1 decade ago Jun 12, 2013, 11:12 p.m. EDT
The following is useful, at least for relatively strong fields.

First, recall that B = mu_0 * mu_r * H

For type-1010 steel (which has much similarity to soft iron) the following expression provides a reasonable fit over a wide range:

mu_r = 1.0 + 2500*(1-tanh(2.7*B)^450)

where B is expressed in Tesla.
tanh = hyperbolic tangent.

So, to clarify: Compute tanh of 2.7*B. Then raise that to the 450 power. Subtract that result from 1. Multiply by 2500. Then add 1. And that will get you a surprisingly good approximation to mu_r.

I hope that helps.
The following is useful, at least for relatively strong fields. First, recall that B = mu_0 * mu_r * H For type-1010 steel (which has much similarity to soft iron) the following expression provides a reasonable fit over a wide range: mu_r = 1.0 + 2500*(1-tanh(2.7*B)^450) where B is expressed in Tesla. tanh = hyperbolic tangent. So, to clarify: Compute tanh of 2.7*B. Then raise that to the 450 power. Subtract that result from 1. Multiply by 2500. Then add 1. And that will get you a surprisingly good approximation to mu_r. I hope that helps.
Fadi Nazzal
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Posted: 1 decade ago Jun 13, 2013, 9:33 a.m. EDT
That's helpful
I don't know how to thank you Robert :)

But can I ask how could one get like this expression for other Ferro's ?

regards
That's helpful I don't know how to thank you Robert :) But can I ask how could one get like this expression for other Ferro's ? regards
Sumeet Chaudhary
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Posted: 9 years ago Mar 8, 2016, 11:46 a.m. EST
Hi Robert,

Could you please give me the reference for this equation:

mu_r = 1.0 + 2500*(1-tanh(2.7*B)^450)

where B is expressed in Tesla.
tanh = hyperbolic tangent.


With regards,
Sumeet
Hi Robert, Could you please give me the reference for this equation: mu_r = 1.0 + 2500*(1-tanh(2.7*B)^450) where B is expressed in Tesla. tanh = hyperbolic tangent. With regards, Sumeet
Robert Koslover Certified Consultant
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Posted: 9 years ago Apr 5, 2016, 2:29 p.m. EDT
It was from my ad-hoc curve fit to B vs. H data tabulated in Fig. 3, page 5 of: Yadav, S., "Finite Element Magnetic Analysis of the Cornell Three-Pole Wiggler Model," Fermi National Accelerator Laboratory (Fermilab) report TD-01-067, Sept. 28, 2001. Note that the report states that the data were "taken from Opera."
It was from my ad-hoc curve fit to B vs. H data tabulated in Fig. 3, page 5 of: Yadav, S., "Finite Element Magnetic Analysis of the Cornell Three-Pole Wiggler Model," Fermi National Accelerator Laboratory (Fermilab) report TD-01-067, Sept. 28, 2001. Note that the report states that the data were "taken from Opera."

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