The Electric Currents, Single Layer Shell Interface
The Electric Currents, Single Layer Shell (ecs) interface (), found under the AC/DC>Electromagnetics and Mechanics>Piezoresistivity branch when adding a physics interface, is a legacy interface used to compute electric field, current, and potential distributions in thin conducting shells under conditions where inductive effects are negligible; that is, when the skin depth is much larger than the studied device. It supports stationary, frequency-domain, small-signal analysis, and time-domain modeling on edges in 2D and faces in 3D
In earlier version this interface was called Electric Currents, Shell. It has been replaced by The Electric Currents in Shells Interface, which is found under the AC/DC branch ().
The physics interface solves a current conservation equation based on Ohm's law using the scalar electric potential as the dependent variable.
Current Conservation is the main node, which adds the equation for the electric potential and provides a Settings window for defining the electrical conductivity as well as the constitutive relation for the electric displacement field and its associated material properties such as the relative permittivity.
When this physics interface is added, these default nodes are also added to the Model Builder— Current Conservation, Electric Insulation (the default edge or point condition), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, edge or point conditions and current sources. You can also right-click Electric Currents, Single Layer Shell to select physics features from the context menu.
Except where described here, the majority of the Settings windows are the same as for the Electrostatics and Electric Currents interfaces as referenced. The only difference are:
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For 3D components, boundaries are selected instead of domains, and edges instead of boundaries.
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For 2D and 2D axisymmetric components, boundaries are selected instead of domains, and points instead of edges and boundaries.
For a more extensive introduction to the physics and equations implemented by this physics interface, see the Theory for the Electric Currents, Single Layer Shell Interface.
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is ecs.
Out-of-Plane Thickness
For 2D components, enter a value or expression for the Thickness d. The default value is 1 unit length.
Use the Change Thickness (Out-of-Plane) node to define specific boundaries or points instead of a global setting for the thickness.
Shell Thickness
Enter a value or expression for the Shell thickness ds (SI unit: m). The default value is 1 cm.
When modeling with shells, the Shell Thickness section defines a parameter that enters the equations everywhere. It is available in all dimensions.
This is unrelated to the Change Thickness (Out-of-Plane) node, which is only available in 2D and represents the out-of-plane length of the shell, which is being modeled as a cross-section.
When modeling in 2D, this means that on the physics interface Settings window, there are two sections — the Shell Thickness and Out-of-Plane Thickness — available, as well as two feature nodes — Change Shell Thickness and Change Thickness (Out-of-Plane).
Manual Terminal Sweep Settings
Enter a Reference impedance Zref (SI unit: Ω). The default is 50 Ω.
Select the Activate manual terminal sweep check box to switch on the sweep and invoke a parametric sweep over the terminals. Enter a Sweep parameter name to assign a specific name to the variable that controls the terminal number solved for during the sweep. The default is PortName. The generated lumped parameters are in the form of capacitance matrix elements. The terminal settings must consistently be of either fixed voltage or fixed charge type.
The lumped parameters are subject to Touchstone file export. Enter a file path or Browse for a file. Select a Parameter format (value pairs) for the Touchstone export — Magnitude and angle (MA) (the default), Magnitude in dB and angle (DB), or Real and imaginary parts (RI). Select an option from the If file exists list — Overwrite or Create new. Select a Parameter to export — Z (the default), Y, or S.
Dependent Variables
The dependent variable (field variable) is for the Electric potential V. The name can be changed but the names of fields and dependent variables must be unique within a model.
Discretization
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Computing Lumped Parameters
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Boundary, Edge, Point, and Pair Nodes for the Electric Currents, Single Layer Shell Interface