Home / Examples / Magnetic Analysis (Gauss, Static Analysis/Harmonic analysis) / Example 28: Inductor with Superimposed DC (Minor Loop Permeability)

Example 28: Inductor with DC Superimposed (Minor Loop Permeability)

General

• The inductance of an inductor with DC superimposed is analyzed.
   

• The minor-loop permeability is used.
  

• This example is a static analysis. The high-frequency characteristics such as skin effect are not taken into account.
  See Example 36 for high-frequency analysis.
   

• The vectors of the magnetic field and the magnetic flux density are solved.
   

• Unless specified in the list below, the default conditions will be applied.
   

• Obtain this session's project file. (Right-click and choose 'Save link as')




• Results will vary depending on Femtet version and the PC environment.

 

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

 

 

Analysis Conditions

Item	Settings
Solver	Magnetic Analysis [Gauss]
Analysis Type	Static Analysis
Options	N/A

Model

A loop coil (coil) and a magnetic core (core) with gap are placed.

As the magnetic field concentrates at the gap of the magnetic core, small mesh size is applied (0.2mm).

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name	Mesh Size
1/Solid	Coil	008_Cu *	0.5
9/Solid	NonL	NonL_mu0_2	0.5

* Available from the material DB

 

Nonlinear material is defined on the nonlinearity table.

First, the distribution of the magnetic field is solved using the B-H curve for the major loop permeability.
Then, using the distribution of the magnetic field, and the B-H curve for the minor loop permeability, the permeability is redetermined and the inductance is calculated. 

Material Name	Tab	Settings
NonL_mu0_2	Permeability	Material Type: Soft Magnetic Material\n(with Minor Loop) Magnetization Characteristic Type: Select B-H curve   B-H Curve Table Magnetic Field [A/m] Magnetic Flux Density [T] 0 0 58 0.42 90 0.8 180 1.19 380 1.37 1100 1.48 2000 1.55 3000 1.608 11000 1.81 20000 1.91 80000 2.15   This B-H curve is for DC bias. It is called Major Loop.
	Permeability for Minor Loop	Magnetization Characteristic Type: Select B-H curve   B-H Curve Table Magnetic Field [A/m] Magnetic Flux Density [T] 0 0 58 0.21 90 0.4 180 0.595 380 0.685 1100 0.74 2000 0.775 3000 0.84 11000 0.905 20000 0.955 80000 1.075   This B-H curve is for AC operation. It is called Minor Loop.

 

Body attribute is set up as follows to apply current to the coil.

Enter the direct current value.

AC current cannot be given. It is assumed to be significantly small compared to DC current.

Body Attribute Name	Tab	Settings
Coil	Current	Waveform: Constant Current: 2 [A] Turns: 100 [Turns] Direction: Loop Coil/Magnetic Field Direction Magnetic Field Vector: X=0, Y=0, Z=1

Boundary Conditions

No setting.

Results

To see the results of inductance calculation, go to the [Results] tab

 

 

 and click [Show Numerical Summary Table] .

 

The vectors of the magnetic flux density generated by the direct current in the inductor are shown below.

• The results other than inductance and coupling coefficient are acquired with the direct current.

 

 

The figure below shows the inductance when [Use the minor-loop permeability] is deselected for NonL_mu0_2

 

 

It is greater than the value calculated with minor-loop permeability.

This is because the permeability is evaluated greater when the major-loop slope is steeper than the minor-loop slope.