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[xzycsu1990]

Hello All,

I tried to define the BH curve for a new material in Maxwell software package, but met some problems. I followed the online help topic "Specifying a BH Curve for Nonlinear Relative Permeability".

The B starts from 0 value. B and H increase monotonically, and I checked that the del_B/del_H increases. But when I click the Ok button, the error pops out. It says "the slope of BH curve may not be less than that of free space anywhere along the curve".

I also attached the initial data for BH data I used to define BH curve. Basically, we have a machine which can measure the M-H curve, then I converted the M-H data to B-H data.

Anyone suggestions to solve this problem?

 

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[Mark Solveson]

The first data point should be (0,0).  Then the following points should continue in the 1st quadrant of the BH curve.  
Your data shows the 2nd and 3rd data points are in the 2nd quadrant (because H is negative for those points).  

Here are some additional requirements:  
Best Practice for BH Curve Point Definition Data points for a curve can either be entered manually or imported from a file. The following guidelines should be used when defining the BH curve points.

• For a Normal BH curve, the slope of the curve cannot be less than that of free space anywhere along the curve.


• For an Intrinsic BH curve, the slope of the curve cannot be less than 0.


• The value of B must increase along the curve.


• The first data points for B and H must be 0 (zero).


• The data points representing the BH curve should have enough points for accurate representation of the curve. 20 or more points should be specified with increased representation on the "knee" of the curve.


• Since BH operating points in the FEA solution may extend beyond the input BH data set, the BH data set is extrapolated in Maxwell. The slope of the last two user-defined data points is used to extrapolate the BH curve, and thus should be as close to mu0 as possible.

[AndyJP]

why don't Ansys simply call Bi-H as M-H, since saturation is already called Ms ? Or 4piM-H, if you want it in CGS, or I-H, or J-H for those who don't like M in Si (meanwhile, J is taken for current density, but is also often used for micro-magnetic momentum). This creates confusion, when you use one letter in general dialog, and another in details setup.nThere can be various conversion rules depending on demagnetization model in the measuring setup, but Ansys simply adds H field to magnetization, as B=Bi+H, which fully justifies replacing Bi with M, which would make more sense.nO.K. speaking honestly, Ansys uses Magnetic Saturation starting from [M],nBut the manual explains it as:n

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