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Home / Examples / Magnetic Analysis (Gauss, Static Analysis/Harmonic analysis) / Example 36: Inductor with Superimposed DC (High Frequency)
Example 36: Inductor with Superimposed DC (High Frequency)
General
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The inductance of a high-frequency inductor with superimposed DC is analyzed.
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The minor-loop permeability is used.
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This is an harmonic analysis. The high-frequency characteristics such as skin effect are taken into account.
See Example 28 for static analysis.
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The vectors of the magnetic field and the magnetic flux density are solved.
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Unless specified in the list below, the default conditions will be applied.
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Obtain this session's project file. (Right-click and choose 'Save link as')
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Results will vary depending on Femtet version and the PC environment.
Analysis Space
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Item |
Settings |
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Analysis Space |
3D |
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Model Unit |
mm |
Analysis Conditions
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Item |
Settings |
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Solver |
Magnetic Analysis [Gauss] |
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Analysis Type |
Harmonic Analysis |
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Options |
None |
The frequency of AC current is set to 1 [MHz].
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Tab |
Setting Item |
Settings |
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Mesh |
Frequency-Dependent Meshing |
Reference Frequency: 1x106 [Hz] |
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Harmonic analysis |
Sweep Type |
Single Frequency |
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Frequency |
1×106 [Hz] |
Set the Mesh Tab as follows.
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Tab |
Setting Item |
Settings |
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Mesh |
Meshing Setup |
Automatically set the general mesh size: Deselect General Mesh Size: 2 [mm] |
Model
A helical solid body Coil (coil) is defined.
Its inflow/outflow faces are extended to the outside of the air domain. They contact the electric wall of outer boundary condition.
In the magnetic harmonic analysis, inflow/outflow faces must be outside of the air domain. (for the purpose of calculation with FEM)
In this example, air domain is set to be created automatically. Therefore, the inflow/outflow faces are extended to be the outside of air domain.
Body Attributes and Materials
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Body Number/Type |
Body Attribute Name |
Material Name |
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0/Solid |
Coil |
008_Cu * |
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4/Solid |
Coil |
008_Cu * |
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5/Solid |
Coil |
008_Cu * |
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6/Solid |
Core |
Core_Nonl_Minor |
* Available from the material DB
Nonlinear material is defined on the nonlinearity table.
When DC is superimposed, BH curve of magnetic materials is on the major loop.
When AC is applied, BH curve of magnetic materials is on the minor loop.
First, the distribution of the magnetic field is solved using the B-H curve for the major loop.
Then, using the distribution of the magnetic field, and the B-H curve for the minor loop, the permeability is reassigned, and the inductance is calculated in the harmonic analysis.
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Material Name |
Tab |
Settings |
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Core_Nonl_Minor |
Permeability |
Material Type: Soft Magnetic Material (with minor loop) Magnetization Characteristic Type: Select B-H curve B-H Curve Table
This B-H curve is for DC bias. |
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Permeability for Minor Loop |
Magnetization Characteristic Type: Select B-H curve
B-H Curve Table
This B-H curve is for AC operation. |
Body attribute is set up as follows to apply current to the coil.
The value of current set here will be the value of the superimposed DC.
AC current cannot be given. It is assumed to be significantly small compared to DC current.
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Body Attribute Name |
Tab |
Setting |
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Coil |
Current |
Select Specify the AC value in the superimposed DC analysis. Waveform: AC Superimposed DC: 1000 [A] Alternating Current: 10 [A] Turns: 1 [Turns] Direction: Specify Inflow/Outflow faces Select Inflow Face and Outflow Face. |
Boundary conditions
No setting.
Results
To see the results of inductance calculation, go to the [Results] tab
and click [Show Numerical Summary Table] 
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Switch to display the results by AC only as indicated by red below.
A contour diagram of the magnetic flux density created by the direct current in the inductor is shown below.
The result display of DC and AC can be switched in the combo box as below.
