New Functionality

This release of the AC/DC Module includes a number of new capabilities. Some of the most important ones are the following:

  • Electric and magnetic point dipoles allow for easy and computationally efficient incorporation of electromagnetic sources in models. Many coils and electrostatic applications can be approximated by one or more point dipoles.
  • The Transition boundary condition for metallic layers of arbitrary thickness provides accurate modeling of geometrically thin metal sheets without having to mesh the thickness. This substantially helps to reduce the number of elements and the problem size. The layer can be of arbitrary electrical thickness (measured relative to the skin depth) and have a more or less pronounced discontinuity in the tangential electric field.
  • The Contact Resistance boundary condition for efficient modeling of thin resistive sheets provides accurate modeling of geometrically thin highly resistive sheets without having to mesh the thickness. This substantially helps to reduce the number of elements and the problem size. The type of layer modeled using the contact resistance condition typically has a discontinuity in the normal electric field.
  • Single-turn coil domain and multi-turn coil domain modeling in 2D allow for easy modeling of coil domains in 2D and also support connection to electrical circuits (integrated with the new Electrical Circuit interface, described below). One or more geometrical domains can be assigned as voltage or current-driven coil. More than one geometrical domain can be treated as belonging to the same coil. This functionality replaces the use of manual model couplings in previous versions.
  • The new Electrical Circuit physics interface with predefined passive and active components is integrated with all the other interfaces in the AC/DC Module via the terminal boundary condition and the single-turn and multi-turn coil domain functionality. It is now possible to build electrical circuits directly in the Model Builder. SPICE netlists are imported and translated into native and editable COMSOL circuit elements in the Model Builder.
  • Port/Terminal sweep for frequency dependent lumped parameter calculations in the graphical user interface makes it easy to compute full lumped parameter matrices. These can be exported in the text-based Touchstone file format.

Backward Compatibility

All backward compatibility issues are planned to be solved for version 4.0a unless explicitly stated.

Change in Dependent Variables

Version 4.0 has a comprehensive set of inductive formulations based on the magnetic vector potential. These cover all modeling situations except for situations with strongly nonlinear conductivity (superconductors) for which magnetic field H-based formulations are more suitable.

The 2D formulations based on the magnetic field H as dependent variable in version 3.5a are not yet included in version 4.0. A full set (3D, 2D and 2D axisymmetry) of H based formulations is planned for version 4.1.

Models created in version 3.5a that are built using an H based formulation will not include any physics interface settings when opened in version 4.0. Geometrical data and definitions (constants and expressions) will be imported and the physics can manually be added using the (vector potential based) Magnetic Fields physics interface.

Cylindrical Infinite Elements in 3D

Cylindrical infinite elements in 3D are not yet implemented. Possible work-arounds are to use Cartesian or spherical infinite elements instead.

Pair Boundary Conditions

Assembly Pair boundary conditions are not implemented in 4.0, except for continuity.

A new set of slit-based, discontinuous boundary conditions, which do not require assemblies are introduced in 4.0. An example of such a boundary condition is the Contact Resistance boundary condition found in Electric Currents physics interface. In most modeling situations these can replace the assembly pair boundary conditions.

The pair boundary conditions from 3.5a models are not loaded automatically but can be manually added using the new slit conditions in version 4.0.

Shell, Conductive Media DC

Shell, Conductive Media DC application modes from version 3.5a models are not automatically imported into version 4.0.

Geometrical data and definitions (constants and expressions) are imported and you can add the physics manually.

Rotating Machinery

The moving mesh interface for rotating machinery is not yet implemented in version 4.0.

However, the Moving Mesh (ALE) physics interface is much easier to use compared to previous versions. You can use this interface to manually implement rotating machinery, which only requires the description of the x and y displacements for a rotating device.

Figure 1-1: Example of clock-wise rotation that can be manually entered in the Moving Mesh (ALE) interface in version 4.0.