AC/DC Module Updates
New Formulation for the Electrostatics Interface
The Electrostatics interface now includes a new equation formulation for more accurate electrostatic force calculations, which is particularly useful when modeling MEMS devices such as accelerometers and gyroscopes. By directly solving for the electric displacement field, this approach improves accuracy in geometries with sharp corners, enabling more accurate force evaluations, even for coarser meshes. Unlike the traditional potential-based formulation, the new method uses a mixed formulation, solving two equations — one for the electric displacement field (D) and another for the electric potential (V). In version 6.3, this enhanced formulation is available as an option, designated as Mixed finite element, for both 2D and 3D electrostatics. Mixed finite element is the default discretization option for the Electromechanics interfaces when using the MEMS Module or the AC/DC Module combined with the Structural Mechanics Module. This new formulation can be seen in the Micromachined Gyroscope with Mixed Formulation tutorial model.
Extensive Support for Modeling Dispersion, Including Biological Tissues
For both the Electrostatics interface and the Electric Currents interface, three new dispersive dielectric material models are available: Cole–Cole, Havriliak–Negami, and User defined. These models are available for frequency-domain studies as well as transient studies. The models are based on the Partial Fraction Fit function introduced in the previous version, which means that the dispersive materials can also be fitted directly onto measured data.
Furthermore, the existing Multipole Debye dispersive material model can be used in combination with material data in the new Biological Tissues folder in the AC/DC Module material library. This folder contains values for the electrical conductivity, relative permittivity, and reference temperature, together with the relaxation times and relative permittivity contributions of several Debye poles, for 54 biological tissue types. This material data is particularly useful for medical applications.
High-Frequency Loss and Homogenized Litz Coil Conductor Model
The Homogenized multiturn conductor model in the Coil feature now includes a High-frequency effective loss model that is enabled by default. In the frequency domain, this model assigns an effective wire conductivity and complex permeability to model the field distribution and AC resistance of a fully resolved coil, accounting for skin and proximity effects. Additionally, a new Wire properties option, From resistance and mutually coupled circuit, links the coil to an internal circuit to simulate inductive loss in both the time and frequency domains.
The Homogenized litz coil conductor model includes support for high-frequency effective loss and makes it possible to specify strand count and DC resistance per unit length, compensating for resistance added by twisting patterns. Additionally, litz wire resistance per unit length can be set using specification sheets, measurements, or frequency-dependent expressions.
The following tutorial models demonstrate these new features:
New Laminated Core Feature
The new Laminated Core feature enables efficient modeling of laminated cores in transformers, electromechanical actuators, and electric motors by approximating the laminae as an anisotropic effective medium. The feature supports both linear and nonlinear magnetic properties, including Relative permeability, B-H curve, and Effective B-H curve. Users can set the Stacking direction and adjust the Stacking factor to specify the ratio of magnetic to nonmagnetic material. Additionally, resistive and magnetic losses can be included using empirical models such as the Steinmetz or Bertotti models. The Laminated Core feature is available in the Magnetic Fields interface; the Magnetic Fields, No Currents interface; and the Rotating Machinery, Magnetic interface.
The following tutorial models showcase the Laminated Core feature:
Improved Usability for Circuit Connections
The usability of circuit connections has been significantly improved, making it easier to connect domain features — for example, to connect the Electric Currents or Magnetic Fields interface to the Electrical Circuit interface — using the Terminal and Coil features. Automated functionality now handles the process of completing circuit connections when a domain or boundary feature is linked to an electrical circuit. Additionally, circuit import and export capabilities are now accessible through the COMSOL API for use with Java, enabling apps, model methods, or add-ins to retrieve or export circuits automatically. This is especially useful for lumped circuit extraction, where circuits are generated based on lumped resistance, capacitance, and inductance matrices derived from finite element models. The following tutorial models highlight these new improvements:
New Electromechanics Multiphysics Interfaces
The new Electromechanics, Shell and Electromechanics, Membrane interfaces simplify modeling the deformation of thin structures, such as microphone membranes, influenced by electrostatic forces. These interfaces automatically include the Electromechanics, Boundary multiphysics coupling for seamless integration with shell or membrane elements, and they use the Electrostatics interface to model the electric field. Demonstrated in the Brüel & Kjær 4134 Condenser Microphone and Axisymmetric Condenser Microphone tutorial models, these interfaces also require the Structural Mechanics Module.
New and Updated Models, New App, and New Add-In
COMSOL Multiphysics® version 6.3 brings new and updated models, a new app, and a new add-in to the AC/DC Module.
Permanent Magnet Motor in Steady State
Piezomagnetic Cell Rover
B-H Curve Checker App
Circuit Extractor Add-In
