Simulate Static and Low-Frequency Electromagnetics with the AC/DC Module

Simulation Software for Low-Frequency Electromagnetics and Electromechanical Components

Analyzing electromagnetic systems and processes that encompass static and low-frequency ranges requires a powerful and flexible simulation tool. The AC/DC Module add-on to the COMSOL Multiphysics® platform provides you with a wide range of modeling features and numerical methods for investigating electromagnetic fields and EMI/EMC by solving Maxwell's equations.

The multiphysics capabilities of the COMSOL® software make it possible to investigate the impact of other physical effects, such as heat transfer, structural mechanics, and acoustics, on an electromagnetics model.

What You Get with the AC/DC Module

When you expand COMSOL Multiphysics® with the AC/DC Module, you unlock features for specialized low-frequency electromagnetics modeling in addition to the core functionality of the COMSOL Multiphysics® software platform.

The AC/DC Module includes the tools necessary for modeling:

  • Capacitors
  • Inductors
  • Insulators
  • Dielectric stress
  • Coils
  • Motors
  • Sensors
  • Solenoids
  • Circuit parameter extraction (R-, L-, Z-matrices)
  • Parasitic capacitance and inductance
  • Combined SPICE circuit and field simulations
  • Electric welding
  • Electric insulation
  • Electromagnetic shielding
  • Capacitive touchscreens
  • Magnetic bearings
  • Electromigration
  • Induction furnaces
  • Induction logging
  • Dielectrics
  • Generators
  • Permanent magnets
  • Electromagnets
  • Actuators
  • Plungers
  • Transformers
  • Transmission lines
  • Graphene
  • Electromachinery
  • Electronics reliability
  • Electrical contact resistance
  • Electromagnetic fields in porous media
An example of modeling transformers with the AC/DC Module. An E-core transformer example model that takes into account the effect of a nonlinear B-H curve in the soft-iron core. The results include the magnetic and electric fields, the magnetic saturation effect, transient response, and more.

Multiphysics Couplings

Included in the AC/DC Module:

  • Induction heating
  • Joule heating and resistive heating
  • Deformation and stress due to electromagnetic force and torque
  • Lorentz forces in solids and fluids

Accessible with additional modules:

  • Heat radiation
  • Thermal contact resistance
  • Bioheating
  • Electrostatic deformation
  • Piezoelectric effect
  • Piezoresistive effect
  • Electrostriction
  • Magnetostriction
  • Thermoelectric effect
  • Inductively coupled plasma
  • Capacitively coupled plasma
  • Tissue ablation
  • Charged particle tracing
  • Dielectrophoresis
  • General single- and multiphysics optimization
An example of modeling the heating of a steel billet with the AC/DC Module. The temperature in a steel billet is shown as well as the magnetic field around and current within the coils.

AC/DC Module Features and Functionality

Explore the features and functionality of the AC/DC Module in more detail by expanding the sections below.
The AC/DC Module comes with a selection of physics interfaces for setting up analyses in a number of application areas, such as electrostatics, electric currents, magnetostatics, and time-varying electromagnetic fields including induction effects. You can form combinations of these interfaces to get more general modeling capabilities.

Did You Know? A physics interface is a user interface for a specific physics area that defines equations together with settings for mesh generation, solvers, visualization, and results.

Physics interfaces in the AC/DC Module:

  • Electric Currents with Current Conservation
  • Electric Currents, Shell
  • Electrical Circuit with SPICE netlist import
  • Electrostatics with Charge Conservation
  • Magnetic and Electric Fields
  • Magnetic Field Formulation
  • Magnetic Fields
  • Magnetic Fields, No Currents
  • Particle Field Interaction, Relativistic
  • Rotating Machinery in 2D and 3D, Magnetic
  • Electrostatics, Boundary Elements
  • Magnetic Fields, No Currents, Boundary Elements
A screenshot of the COMSOL software GUI when modeling a tunable capacitor. A tunable capacitor is modeled with a hybrid FEM-BEM approach with an automatic coupling between the two in order to compute the electric potential.

In addition to fundamental boundary conditions — such as potentials, currents, charges, and field values — a range of advanced boundary conditions are included. Some of these, including the Terminal, Floating Potential, and Circuit Terminal boundary conditions, are used to extract equivalent circuit parameters from a 2D or 3D model such as resistance, capacitance, inductance, and impedance values and matrices.

Boundary conditions in the AC/DC Module:

  • Circuit Terminal
  • Contact Resistance
  • Dielectric Shielding
  • Distributed Capacitance
  • Distributed Impedance
  • Distributed Resistance
  • Electric Shielding
  • Electrical Contact
  • Lumped Port
  • Periodic Boundary Condition
  • Sector Symmetry
  • Surface Impedance
  • Surface Magnetic Current
  • Thin Low Permeability Gap
  • Transition
  • Coil Excitation
  • Homogenized Multiturn
  • Single Conductor
  • Floating Potential
  • Magnetic Field
  • Magnetic Flux Density
  • Magnetic Insulation
  • Magnetic Potential
  • Perfect Magnetic Conductor
  • Surface Current
  • Boundary Current Source
  • Continuity
  • Displacement Field
  • Electric Insulation
  • Electric Potential
  • Ground/Zero Potential
  • Normal Current Density
  • Surface Charge Density
  • Zero Charge
  • Magnetic Shielding
  • B-H and H-B Curve Input
An example of a model for analyzing touchscreen device designs. A touchscreen device model. Electrodes are frequently modeled with fixed potential, charge, or current values together with floating potential conditions for metallic surfaces of unknown potential.

Modeling Thin Structures

For modeling very thin structures, you can use shell formulations that are available for direct currents, electrostatics, magnetostatics, and induction simulations. Electromagnetic shell modeling makes it possible to replace the thickness of a thin solid in a CAD model with a physical property of a surface resulting in a much more efficient representation.

Unbounded or Large Domains

For accurate modeling of unbounded or large modeling domains, infinite elements are available for both electric and magnetic fields. For electrostatics and magnetostatics modeling, the boundary element method (BEM) is available as an alternative method for modeling large or infinite regions and works in combination with physics interfaces based on the finite element method (FEM).

Coil Modeling

Specialized coil features can be used to greatly simplify the setup process of coils for a range of magnetostatics and low-frequency electromagnetics models. In many such applications, the magnetic field is generated by electric currents flowing in conductive materials; for example, cables, wires, coils, or solenoids. The specialized coil features are used to easily model these structures and to translate lumped quantities, like currents and voltages, into distributed quantities, such as current densities and electric fields. Single-conductor and homogenized multiturn coils can be defined in full 3D or 2D axially symmetric models.

Rotating Machinery and Linear Motion

Using the built-in interface for rotating machinery, it is easy to model motors and generators. You can, for example, understand the behavior of induction or PM motors, particularly by capturing the eddy current losses that occur within the magnets. In any model that is used for simulating electromagnetic motion, you can examine the rigid or flexible body dynamics under the influence of magnetic forces and torques, induced currents, and mechanical load and spring configurations.

A general-purpose moving mesh functionality makes it possible to model linear motion. This is important for understanding the operation of components involving plungers, such as in magnetic power switches and general actuators.

A submarine model shown in the COMSOL software GUI.

A submarine is modeled with thin structures via the Magnetic Shielding boundary condition. The magnetic signature can be found at large distances with the boundary element method.


You can choose from a large material database that includes:

  • Ferromagnetic materials
  • Ferrimagnetic materials
  • B-H curves
  • H-B curves

In addition, you can use materials from libraries made available by other add-on products.

Materials can be spatially varying, anisotropic, time-varying, lossy, complex-valued, and discontinuous. It is easy to expand the scope of a simulation with little additional work. You can define your own materials using mathematical expressions, look-up tables, or combinations of both. Alternatively, you can use externally defined materials written in C-code.

More generally, by using the equation-based modeling functionality, you can modify boundary conditions, material properties, and equations to customize a simulation for your specific needs.

An example of using equation-based modeling with the AC/DC Module to include custom materials. A Jiles-Atherton anisotropic hysteretic material model is used to model the magnetic field in an e-core model, with the results showing a B-H curve and the magnetic flux density norm.

The AC/DC Module offers automatic, semiautomatic, and adaptive mesh generation. Under the hood, the AC/DC Module formulates and solves Maxwell’s equations using FEM, BEM, or a combination of both methods, in concert with state-of-the-art solvers. Several types of finite element and boundary element mesh elements are available.

Numerical methods in the AC/DC Module:

  • FEM
  • BEM
  • Linear and high-order nodal-based and edge element discretizations
  • Combinations of tetrahedral, prismatic, pyramidal, hexahedral, triangular, and quadrilateral elements
  • Linear and nonlinear solvers

Study types in the AC/DC Module:

  • Static
  • Frequency domain
  • Time domain
  • Automated terminal sweeps for circuit parameter extraction
An example of solving electric and magnetic field models with the AC/DC Module.

It is easy to include multiple solver steps by adding studies. In this generator example, Coil Geometry Analysis, Stationary, and Time Dependent studies are added all at once in sequential order.

Default visualizations are automatically adapted to the interface you have used and include plots of electric and magnetic fields, currents, charges, and voltages. You can easily add custom visualizations of any field quantity as well as composite expressions of field quantities and their derivatives.

The postprocessing tools can be used to generate lumped parameter matrices, such as capacitance or impedance matrices, as well as integrated, averaged, maximum, and minimum values. For example, you can use a maximum field evaluation to make sure the dielectric strength is not exceeded anywhere in your model, or get the total charge by integrating the charge density over a set of surfaces. By using cut-lines and cut-surface, it is possible to examine the field values on arbitrary cross sections of a model.

Postprocessing and visualization features in the AC/DC Module:

  • Voltage plots
  • Electric field plots
  • Magnetic field plots
  • Current density plots
  • Charge density plots
  • Arbitrary expressions of physical quantities
  • Derived tabulated quantities such as R-, L-, C-, Z-, Y-, and S-matrices
  • Total charge and current
  • Force and torque vs. time
An example of visualizing EM plots with the AC/DC Module. The opening and closing of a power switch is modeled and then visualized with postprocessing tools. The electric losses are shown for three different times, simultaneously.

Make your simulation process more efficient with the built-in Application Builder by turning your models into specialized apps with customized inputs and outputs. You can distribute the apps you make to colleagues without simulation expertise so they can perform repetitive analyses on their own, streamlining the design process.

The workflow is simple:

  1. Transform your EM model into a specialized user interface (an app)
  2. Customize the app to your needs by selecting inputs and outputs for the app's users
  3. Add optional code for user-interface logic or additional nonstandard operations
  4. Use the COMSOL Server™ product to deploy the app to other members of your team or beyond
  5. Enable your team to run their own design analyses without further assistance

You can expand the capabilities of simulation throughout your team, organization, classroom, or customer/vendor base by building and using simulation apps.

An example of an app built for efficiently simulating touchscreens. The Touchscreen Simulator app was created with COMSOL Multiphysics® and the AC/DC Module. By building apps like this one, you can help streamline the EM device design process.

If you use the MATLAB® software, you can easily drive COMSOL Multiphysics® simulations with MATLAB® scripts and functions. The LiveLink™ for MATLAB® interfacing product enables you to access COMSOL® operations through MATLAB® commands and blend these commands with your existing MATLAB® code, directly within the MATLAB® environment.

In order to make it easy for you to analyze electromagnetic properties of CAD models and electronic layouts, COMSOL offers the ECAD Import Module, CAD Import Module, Design 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 the COMSOL Multiphysics® software, as well as produce simultaneous parametric sweeps over several model parameters.

You can also synchronize Microsoft® Excel® spreadsheet data with the parameters you define in the COMSOL Multiphysics® environment via the LiveLink™ for Excel® interfacing product.

Available interfacing products include:

  • LiveLink™ for MATLAB®
  • ECAD Import Module
  • CAD Import Module
  • Design Module
  • LiveLink™ products for leading CAD software
  • LiveLink™ for Excel®

View all available interfacing products in the product suite.

An example of importing an IPC-2581 test file into COMSOL Multiphysics. An IPC-2581 test file of a six-layer PCB was imported into COMSOL Multiphysics® with the ECAD Module for simulation analysis. Test case courtesy of Cadence Design Systems, Inc.

Design Electromagnetic Devices and Systems for the Real World

The products, devices, and components you design for the static or low-frequency range need to operate safely in the real world. For a comprehensive analysis, use the COMSOL Multiphysics® software and the AC/DC Module to see how multiple physics affect your design.

Most electromagnetic components, devices, and products are affected by another branch of physics, whether it be heat transfer, structural mechanics, or acoustics, to name a few. For the most accurate study possible, you can examine a variety of these effects simultaneously. The COMSOL Multiphysics® platform enables you to couple multiple physical effects in one software environment.

An example of designing real-world electromagnetic devices with the COMSOL Multiphysics software. An induction motor is modeled with the AC/DC Module and the Multibody Dynamics Module to account for electromechanical effects. The von Mises stress distribution in the housing is shown.

Next Step:
Request a Software

Every business and every simulation need is different. In order to fully evaluate whether or not the COMSOL Multiphysics® software will meet your requirements, you need to contact us. By talking to one of our sales representatives, you will get personalized recommendations and fully documented examples to help you get the most out of your evaluation and guide you to choose the best license option to suit your needs.

Just click on the "Contact COMSOL" button, fill in your contact details and any specific comments or questions, and submit. You will receive a response from a sales representative within one business day.