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.

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 [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.