AC/DC Module

AC/DC Module

Software for Computational Electromagnetics Modeling

Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.

COIL MODELING: The model shows a 50-Hz AC coil wound around a ferromagnetic core. The complex coil winding geometry can be easily modeled using a multiturn coil feature. Visualization shows the magnetic flux density (arrow plot) and the magnetic flux density norm on the ferromagnetic core.

AC/DC Module

Modeling Capacitors, Inductors, Insulators, Coils, Motors, and Sensors

The AC/DC Module is used for simulating electric, magnetic, and electromagnetic fields in static and low-frequency applications. Typical applications include capacitors, inductors, insulators, coils, motors, actuators, and sensors, with dedicated tools for extracting parameters such as resistance, capacitance, inductance, impedance, force, and torque.

Materials and constitutive relations are defined in terms of permittivity, permeability, conductivity, and remanent fields. Material properties are allowed to be spatially varying, time-dependent, anisotropic, and have losses. Both electric and magnetic media can include nonlinearities, such as B-H curves, or even be described by implicitly given equations.

Boundary Conditions and Infinite Elements

The AC/DC Module grants you access to a set of essential boundary conditions such as electric and magnetic potential, electric and magnetic insulation, zero charge, and field and current values as well. In addition, a range of advanced boundary conditions are included, such as terminal conditions for connection with SPICE circuits, floating potentials, conditions for symmetry and periodicity, surface impedance, surface currents, distributed resistance, capacitance, impedance, and contact resistance. For modeling unbounded or large modeling domains, infinite elements are available for both electric and magnetic fields. When an infinite element layer is added to the outside of a finite-sized modeling domain, the field equations are automatically scaled. This makes it possible to represent an infinite domain with a finite-sized model and avoids artificial truncation effects from the model boundaries.  For electrostatics modeling, the boundary element method is available as an alternative method of modeling infinite regions.

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Product Features

  • Bioheating
  • Circuit parameter extraction (R ,L, Z matrices)
  • Combined SPICE circuit and field simulations
  • Contact resistance
  • Current and field distribution and visualization
  • Electric displacement field and dielectric stress
  • Electromagnetic force and torque
  • Electromagnetic shielding
  • Electromechanical deformation
  • Induction heating
  • Lorentz force computation
  • Nonlinear materials including B-H curves
  • Parasitic capacitance and inductance
  • Porous materials
  • Resistive heating

Application Areas

  • Coils and solenoids
  • Electric welding
  • Electric insulation
  • Electromagnetic compatibility (EMC)
  • Electromagnetic interference (EMI)
  • Electromagnetic shielding
  • Electromechanical machinery
  • Electronics reliability and electromigration
  • Induction furnaces
  • Induction logging
  • Insulators, capacitors and dielectrics
  • Motors, generators and other electromechanical machinery
  • Permanent magnets and electromagnets
  • Plungers
  • Sensors
  • Transformers and inductors


As an example of a magnetostatic problem, consider how to model a horseshoe-shaped permanent magnet. One way is to treat the entire magnet as a ferromagnetic material, where the two end sections are defined as being pre-magnetized in different and opposite directions.

» See model.

Induction heating is a method used to heat metals for forging and other applications. Compared with more traditional heating methods, such as gas or electric furnaces, induction heating delivers heating power directly to the piece in a more controlled way and allows for a faster processing time.

The Induction Heating of a Steel Billet application can be used to design a simple induction heating system for a steel billet, consisting of one or more electromagnetic coils through which the billet is moved at a constant velocity. The coils are energized with alternating currents and induce eddy currents in the metallic billet, generating heat due to Joule heating. The billet cross section; the coil number, placement, and size; as well as the initial and ambient temperature and the individual coil currents can all be specified as inputs in the app.

After the solution has been computed, the app plots the billet temperature and current density during the processing. Furthermore, it computes numerical data on the expected temperature ranges in the billet and the power balance of the system.

» See model.

This model shows how to combine an electric circuit simulation with a finite element simulation. The finite element model is an inductor with a nonlinear magnetic core and 1000 turns, where the number of turns is modeled using a distributed current technique.

The circuit is imported into COMSOL Multiphysics as a SPICE netlist, which merges the inductor model and the circuit elements as ODEs.

» See model.

This is the transient model of a single phase E-core transformer using a Multi-Turn Coil Domain. The model includes the effect of a nonlinear B-H curve in the core and shows how to connect the transformer model to the external circuits using Electric Circuit interface. The simulation is performed for two different cases; the first one with a unity turn ratio and second one with a turn ratio of one thousand.

» See model.

Inductors are used in many applications for low pass filtering or for impedance matching of predominantly capacitive loads. They are used in a wide frequency range from near static up to several MHz. An inductor usually has a magnetic core to increase the inductance, while keeping its size small. The magnetic core also reduces the electromagnetic interference with other devices as the magnetic flux tends to stay within it. Because there are only crude analytical or empirical formulas available for calculating impedances, computer simulations or measurements are necessary in the design of inductors. Inductor modeling is in general more complex than the modeling of resistors and capacitors, but similar principles apply. This introductory model uses a design drawn in an external CAD software and is imported for static and frequency domain analysis in the AC/DC Module. In this tutorial, we perform the AC analysis up to computing the frequency dependent impedance.

» See model.

The induced currents in a copper cylinder produce heat that in turn change the electrical conductivity. This means that the field propagation has to be solved simultaneously with the heat transfer through the cylinder and surrounding system.

This model shows this coupling between eddy currents and heat transfer as a tutorial example.

» See model.

The mutual inductance and induced currents between a single turn primary and twenty turn secondary coil in a concentric coplanar arrangement is computed using a frequency domain model. The secondary coil is modeled using a homogenized approach which does not explicitly consider each turn of the coil. The results are compared against analytic predictions.

» See model.

When modeling the propagation of charged particle beams at high currents, the space charge force generated by the beam significantly affects the trajectories of the charged particles. Perturbations to these trajectories, in turn, affect the space charge distribution.

The Charged Particle Tracing interface can use an iterative procedure to efficiently compute the strongly coupled particle trajectories and electric field for systems operating under steady-state conditions. Such a procedure reduces the required number of model particles by several orders of magnitude, compared to methods based on explicit modeling of Coulomb interactions between the beam particles. A mesh refinement study confirms that the solution agrees with the analytical expression for the shape of a nonrelativistic, paraxial beam envelope.

» See model.

In an electrostatically tunable parallel plate capacitor, the distance between the two plates can be modified by a spring, as the applied voltage changes.

For a given voltage difference between the plates, the distance of the two plates can be computed, if the characteristics of the spring are known. Knowledge of this means that the distance between the plates can be tuned via the spring.

In this model, the electrostatic field is simulated out for a given distance.

» See model.

Magnetic prospecting is a geological exploration method that is applicable to certain types of iron ore deposits, in particular those made up of magnetite and hematite. The method consists of measuring the magnetic anomalies (changes in the earth’s magnetic field) due to the presence of magnetic ores.

The Magnetic Prospecting app simulates the effect of a deposit of magnetic ore on the earth’s magnetic field and predicts the measured anomaly at specified measuring points on the surface. You can import heightmap images or digital elevation model (DEM) files to define the orography of the region as well as the geomagnetic field data for the specified location.

The computation generates a plot of the magnetic field on the earth’s surface as well as numerical data of the expected anomaly at specified measurement locations in the region.

» See model.