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Hello, Magnetic Components Fans:

In this blog I use Ansys Maxwell to compute the core loss of a toroidal inductor and validate the results using the manufacturer's material specification sheet for the core. Also, we compare how the B vs H values from the manufacturer's specification sheet matches with values in Maxwell's laminated core model. 



In this section the model setup is described. The geometry consists of two objects, one core and one winding. The winding is copper and the core is AK-Steel-H-0 Carlite.



Isometric View


Top View


Side View



Ampere's law was applied to determine the required current excitation to obtain the required H value that corresponds to the B field value shown in the manufacturer's specification sheet highlighted below.



The B vs H and B vs P curves from the manufacturer's specification sheet was imported in the Maxwell model using the AEDT Sheet Scan tool. 








The Maxwell model's material properties for the core are set. The composition is set to Lamination and the Stacking Factor value is applied, as well as the stacking direction is specified. There are various options for the Core Loss Model and B-P curve is selected to apply the lamination thickness.






We can compute the mass of the core since we know the density from the material properties and we can use Maxwell to compute the volume of the core. Therefore, the mass of the core is

m = Vcore*pcore = (2.74755485758317*E-09 m^3)*(7650 kg*m^-3) = 2.10187946605113E-05 kg



The percent difference of the average core loss in once cycle in steady state is less than 2% with regard to the 1.08 W/kg value in the material specifications sheet table.



We can evaluate a B and H values at a point which coincides with a mesh node of an object. For example, choose the H quantity and select mag. Then choose the core volume geometry, and then select Value. Set the time at which we desire to evaluate the value. Then select Write and save the data to a file which will contain the H values at each mesh node. Repeat these steps to write the B values of each mesh node to a file. Also, add Named Expression for the magnitude of H and B fields. In this example the name expressions are Mag_H and Mag_B. 


Add a point in the model using the coordinates from the B and H values in the saved files from the Write commands. 


Right click on results and choose Create Field's Report and select Rectangular Plot. In the Geometry drop down menu choose the point that was added to the model. Select Field Calculator Expressions and choose Mag_H and Mag_B for the X and Y axis, respectively, as shown below.



The green curve is the BH curve imported from the manufacturer's specification sheet using the Sheet Scan tool. The red point is the BH value at the node of the mesh node with the coordinate determined from the Field's Calculator Write commands. The percent difference of the BH value between the point in the laminated core model and the curve is less than 4%. If the composition of the core is set to solid, and not laminated, the percent difference would be practically zero.



The Field's Calculator was used to compute the average magnetic flux density field value in the cross section of the core and the percent difference compared to the target value of 1.7 T is less than 2%.


Here are field plots of H and B.



Here are field plots of volumetric current density in the ZX plane and magnetic flux density B in the core.







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Post by David A. Giglio, PhD, PE
June 22, 2024