AC/DC Module

Software for Computational Electromagnetics Modeling

Transient model of a single phase E-core transformer that is described by a nonlinear B-H curve in the core. The graph shows the electromagnetic field and current in the primary and secondary windings.

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.

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 the ECAD Import Module. Simulation of such layouts is not limited to electromagnetics.

• PERMANENT MAGNETS: This model presents the static-field modeling of an outward-flux-focusing magnetic rotor using permanent magnets. This magnetic rotor is also known as a Halbach rotor. The use of permanent magnets in rotatory devices like motors, generators, and magnetic gears is becoming more popular due to their non-contact, frictionless operation. This model illustrates how to calculate the magnetic field of a 4-pole pair rotor in 3D by modeling only a single pole of the rotor, using symmetry.
• ECAD IMPORT: The AC/DC Module is used for capacitance and inductance extraction for a planar transformer model imported as an ECAD file. This type of device is used in power supplies and DC/DC converters where a slim high-power design is crucial. The entire layout, including the footprint of the transformer ferrite core, is imported from an ODB++(X) file. The ECAD Import Module is used to read the layout and automatically create a 3D geometry model of the Printed Circuit Board (PCB) and the ferrite core.
• SEMICONDUCTOR MANUFACTURING: A susceptor of graphite is heated through induction. The model shows the temperature distribution inside the susceptor and on the quartz tube.
• MEDICAL TECHNOLOGY: Simulation of the electromagnetic field in a high-voltage generator in an X-ray device. Model courtesy of Comet AG, Switzerland.
• MASS SPECTROMETRY: The AC/DC Module in concert with the Particle Tracing Module. The visualization shows the trajectory of ions in a quadrupole mass spectrometer with a specific charge-to-mass ratio.
• ELECTRICAL MACHINERY: A brushed DC motor simulated with the new 3D rotating machinery user interface. Visualized here: B-field, coil current, axial torque, and rotational angle.

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.

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.

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.

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.

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