• Description

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.

View screenshot »

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.

View screenshot »

Additional Images:

  • MOTOR/GENERATOR: These results show a 3D static analysis of the magnetic fields around a rotor and stator. Permanent magnets and nonlinear magnetic materials are included, and material nonlinearity is modeled via an interpolation function.
  • POWER INDUCTOR: The single-turn coil feature is used to capture the skin effect in the wire, since the skin depth in this coil is comparable to the thickness of the current-carrying wires at the operating frequency. This model shows how to compute both the DC and AC properties of an inductor as well as the admittance and inductance.
  • PERMANENT MAGNET: This introductory example for magnetic field modeling describes a typical horseshoe magnet and iron bar, where the Symmetry condition is used to reduce the problem size. The magnetic fields and forces are computed.
  • MAGNETIC DAMPING: This model simulates structural damping on a conducting solid that is vibrating in a static magnetic field. It computes the effect when a cantilever beam is harmonically excited and placed in a strong magnetic field.
  • MAGNETIC PROSPECTING: Underground iron ore deposits result in magnetic anomalies. This model computes the disturbances in the background magnetic field of the earth due to the presence of an ore deposit. The Reduced Field formulation solves for small perturbations in the background field.

Combine Circuits and Layouts with 2D and 3D Simulations

When considering your electrical components as part of a larger system, the AC/DC Module provides an interface with SPICE circuit lists where you choose circuit elements for further modeling. More complex system models can be exploited using circuit-based modeling while maintaining links to full field models for key devices in the circuit, allowing for design innovation and optimization on both levels. Electronic layouts can be brought in for analysis with the AC/DC Module via theECAD Import Module. Simulation of such layouts is not limited to electromagnetics.

View screenshot »

Connect with CAD, MATLAB®, and Excel®

In order to make it easy for you to analyze electromagnetic properties of mechanical CAD models, COMSOL offers the ECAD Import Module, the CAD Import Module, and LiveLink™ products for leading CAD systems as part of our product suite. The LiveLink products make it possible to keep the parametric CAD model intact in its native environment but still control the geometric dimensions from within COMSOL Multiphysics®, as well as produce simultaneous parametric sweeps over several model parameters. For repetitive modeling tasks, LiveLink™ forMATLAB® for allow you to drive COMSOL® simulations with MATLAB® scripts or functions. Any operation available in the COMSOL Desktop® can alternatively be accessed through MATLAB commands. You can also blend COMSOL commands in the MATLAB environment with your existing MATLAB code. For electromagnetic simulations operated from spreadsheets,LiveLink™ for Excel® offers a convenient alternative to modeling from the COMSOL Desktop with synchronization of spreadsheet data with parameters defined in the COMSOL environment.

Nonlinear Magnetic Materials Database

A database of 165 ferromagnetic and ferrimagnetic materials is included in the AC/DC Module. The database contains BH-curves and HB-curves enabling the material properties to be used in the magnetic fields formulations. The curve data is densely sampled, and has been processed to eliminate hysteresis effects. Outside of the range of experimental data, linear extrapolation is used for maximal numerical stability.

Take Multiphysics into Consideration in Your Designs

Although devices may be principally characterized by electromagnetics, they are also influenced by other types of physics. Thermal effects, for instance, can change a material’s electrical properties, while electromechanical deflections and vibrations in generators need to be fully understood during any design process. The AC/DC Module, being comprehensively integrated in the COMSOL environment, allows for a wide range of physical effects to influence the virtual model.

View screenshot »

Electromagnetic Shells

For very thin structures, the AC/DC Module provides a range of specialized formulations for efficient electromagnetic simulations where the thickness of the structures does not need to be represented as a physical thickness in the geometry model but can instead be represented with a shell. Such thin shell formulations are available for direct currents, electrostatics, magnetostatics, and induction simulations, and is particularly important for electromagnetic shielding within electromagnetic compatibility (EMC) and interference (EMI) applications.

Consistent Workflow for Electromagnetics Modeling

The module's straightforward workflow is described by the following steps: define the geometry, select materials, select a suitable AC/DC interface, define boundary and initial conditions, automatically create the finite element mesh, solve, and visualize the results. All these steps are accessed from the COMSOL Desktop®. AC/DC Module simulations can be connected with every COMSOL product in just about any way imaginable by a suite of preset multiphysics couplings or via user-defined couplings. A typical preset coupling is one between the AC/DC Module and the Particle Tracing Module where electric or magnetic fields affect charged particles that can be assigned to either have mass or be massless. The Optimization Module can be combined with the AC/DC Module for optimization with respect to voltage and current excitation, material properties, geometric dimensions, and more.

View screenshot »

Flexible and Robust

The AC/DC Module includes stationary and dynamic electric and magnetic fields, both in 2D and 3D. Under the hood, the AC/DC Module formulates and solves Maxwell’s equations together with material properties and boundary conditions. The equations are solved using the finite element method with numerically stable edge element discretization in concert with state-of-the-art solvers. The different formulations admit static, frequency-domain, and time-domain simulations. Results are presented in the graphics window through preset plots of electric and magnetic fields, currents and voltages, or as expressions of the physical quantities that you can define freely, as well as derived tabulated quantities.

View screenshot »