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Home / Technical Notes / Electric analysis / Conductive Body
Conductive Body
1. Overview
Conductive body is the body set with "Conductor", "Multilayer electrode", or "Perfect conductor" on the Electric Conductivity tab in its Edit Material Property dialog box. Please note that multilayer electrode can be set only in the electromagnetic analysis.
Conductive bodies are treated as follows.
2. Electric analysis (Coulomb)
(1) Static Analysis (Capacitance)
2. Electric analysis (Coulomb)
(1) Static Analysis (Capacitance)
The boundary condition named "RESERVED_volt_body-attribute-name_serial-number" is applied to the boundary and the inside of the body after meshing. Serial number is assigned to each body. The electric potential of conductive bodies in contact is constant. The potential of conductive bodies not in contact is not the same in most cases. To give the same electric potential to the conductive bodies that are apart, set the floating electrode having the same boundary condition name to the bodies.
(2) Static Analysis (Resistance)
The electric potential inside the conductive body is analyzed. It cannot be set on the Electrode tab of its body attribute.
(3) Harmonic analysis
If it is "perfect conductor", the conductive body will be treated in the same way as (1). If not, no boundary condition is applied and the voltage inside the conductive body is analyzed.
3. Electromagnetic analysis (Hertz)
The electromagnetic waves can penetrate the conductor if the frequency is low.
If the frequency is high and the electromagnetic waves penetrate the conductor only slightly,
more accurate results are obtained by applying the "conductor" boundary condition. If the frequency is low, however,
the boundary condition cannot be used because the inside needs to be analyzed. In such a case,
Femtet will create the conductor boundary condition based on the frequency and the model. Depending on the analysis condition and body type,
the procedures will vary as below.
For the multilayer electrode, unlike conductor, boundary condition is always applied.
If the body is "perfect conductor", the tangential component of the electromagnetic field is nil on its surface, and the electromagnetic field doesn't exist inside.
If the body is "conductor", it is treated as follows.
(1) Conductive solid body in 3D analysis
The boundary condition is automatically applied if the frequency is substantially high, i.e. the thickness of the conductive body* is more than double the skin depth.
"Reference frequency" is the frequency used to calculate the skin depth.
After meshing, the mesh generation module applies the boundary condition named "RESERVED_zero" to the conductor's inside, where the electromagnetic field will be nil.
In addition to that, the "conductor wall" boundary condition named "RESERVED_impedance_material-name" is applied to the conductor's surfaces.
If the body is "conductor" and thinner than double the skin depth, no boundary condition will be applied and its inside is analyzed.
When the boundary condition named "RESERVED_impedane_material-name" is set, sheet body named "RESERVED_dual_body attribute name" also will be created.
This will be an element generated for showing the current distribution on the conductor's surfaces.
For the multilayer electrode, boundary condition is always set. This is the same flow as setting boundary condition for conductor.
Boundary condition name will be "RESERVED_multilayer_material name".
If the body is "perfect conductor", the boundary condition named "RESERVED_zero" is set to the conductor's inside and surfaces.
This function to generate boundary conditions is enabled as follows:
[Analysis Condition Setting] dialog box > [Mesh] tab > Frequency-Dependent Meshing > select "The conductor bodies thicker than the skin depth constitute the boundary condition." (default)
(2) Sheet body in 3D analysis
If the option for [Take thickness of face/edge electrode into account] is not selected on the electromagnetic analysis tab:
The analysis is performed in the same way as when the boundary condition is applied to the faces.
If the option for [Take thickness of face/edge electrode into account] is selected on the electromagnetic analysis tab:
The electromagnetic field inside the conductor is analyzed with the conductor thickness taken into account.
See "Thin Electrode Elements" for details.
(3) Sheet body in 2D waveguide analysis
The conductive body is treated in the same way as (1).
(4) Wire body in 2D waveguide analysis
The conductive body is treated in the same way as (2).
(5) Sheet body in 2D or axisymmetric resonance analysis
The conductive body is treated in the same way as (1).
(6) Wire body in 2D or axisymmetric resonance analysis
Wire body is not supported in this analysis.
* The approximated thickness of body is acquired by dividing its volume by its surface area.
4. Magnetic analysis (Gauss)
(1) Static analysis
No boundary conditions are applied and the inside is analyzed.
(2) Harmonic analysis
If the frequency is substantially high, i.e. the thickness of the conductive body* is more than double the skin depth,
one of the processes below will be applied depending on the selection of [Surface Treatment for Conductors Thicker Than Skin Depth] on the [Mesh tab.
Generate skin meshes
Thin skin-depth meshes are generated on the conductor surfaces.
The skin depth is calculated from the reference frequency.
Apply the surface impedance boundary
The surface impedance boundary is automatically applied to the conductor's surfaces
The inside of the conductive body is not analyzed.
The skin depth is calculated from the reference frequency.
Operations in detail
The surface impedance boundary condition named "RESERVED_impedance_material-name" is applied to the conductor's surfaces. Create sheet body named "RESERVED_dual_body attribute name". This sheet body is used for loss calculation of the conductor.
The boundary condition named "RESERVED_zero" is applied to the conductor's inside, where the magnetic field will be nil.
If the body is "conductor" and thinner than double the skin depth, no boundary condition will be applied and its inside is analyzed.
If the body is "perfect conductor", the boundary condition named "RESERVED_zero" is set to the conductor's inside and surfaces.
(3) Transient analysis
If the frequency is substantially high, i.e. the thickness of the conductive body* is more than double the skin depth,
one of the processes below will be applied depending on the selection of [Surface Treatment for Conductors Thicker Than Skin Depth] on the [Mesh tab.
Generate skin meshes
Thin skin-depth meshes are generated on the conductor surfaces.
The skin depth is calculated from the reference frequency.
* The approximated thickness of body is acquired by dividing its volume by its surface area.