New Functionality in Version 4

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 modeling of electromagnetic sources. 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.
  • Discontinuous interior boundary conditions like electric insulation for electric currents and perfect magnetic conductor for magnetic fields are now available.
  • 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.
  • A new moving mesh interface for rotating machinery is now implemented in version 4.0 where the Moving Mesh (ALE) physics interface is much easier to use compared to previous versions. You can use this interface to implement new rotating machinery models. For backward compatibility for old rotating machinery models, see below.
  • 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 vs. Version 3.5a

Change in Dependent Variables

Version 4 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 interface.

Pair Boundary Conditions

The Contact Resistance, Transition, and Perfect Magnetic Conductor boundary conditions are not yet available as assembly Pair boundary conditions.

A new set of slit-based, discontinuous boundary conditions, which does not require assemblies is introduced in version 4. In most models, this can replace the assembly pair boundary condition.

Reduced Potential

The formulations using a reduced potential are not yet implemented in version 4.0a. They are planned for 4.1.