AC/DC Module Updates
For users of the AC/DC Module, COMSOL Multiphysics® version 5.6 offers a new Magnetic Fields, Currents Only interface, empirical loss models, and various improvements to the existing Electrical Circuit interface. Learn about these and other AC/DC Module updates in more detail below.
New Physics Interface for Inductance Matrix Computations
The new Magnetic Fields, Currents Only interface is designed to efficiently compute the lumped inductance matrix of complex circuits in 3D, such as those commonly found on printed circuit boards (PCBs). It can be used to calculate the partial contributions from magnetic fields generated by open conductors, also known as nonsolenoidal conductors. The ability to handle open conductors significantly reduces modeling complexity for users needing to solve for mutual inductance matrices.
The interface uses the magnetic vector potential as the dependent variable, and computes the magnetic fields generated by currents under the assumption that all regions are nonmagnetic (in other words; that they have a uniform relative magnetic permeability of "one"). This new formulation does not require the conductor currents to be divergence-free. In free space, it returns the value of the Biot–Savart integral. The interface supports the Stationary and the Stationary Source Sweep study steps. The latter is an efficient way of sweeping over many terminals. You can see this interface in use in the new Inductance Matrix Calculation of PCB Coils tutorial model and in the updated Magnetic Field of a Helmholtz Coil model.
Loss Models for Laminated Cores and Yokes in Motors and Transformers
The new Loss Calculation feature uses empirical models (Steinmetz, Bertotti, or User defined) to calculate iron loss caused by magnetic hysteresis, eddy currents, and other effects in (laminated) cores or yokes in, for example, electric motors and transformers. As a fallback option for materials like copper, it is able to provide the cycle average resistive losses.
In the Model Builder, Loss Calculation is available as a subnode to the Ampère's Law node, domain Coil node, Faraday’s Law node, and Magnetic Flux Conservation node. It is available for both Time Dependent and Frequency Domain studies. For Time Dependent studies, the Loss Calculation feature is designed to be used in combination with the dedicated Time to Frequency Losses study step. This study step determines the different harmonics present in the time-dependent solution, and inserts them into one of the frequency-dependent empirical loss models. You can see this new feature in these updated models:
- permanent_magnet_motor_in_3d
- modeling_of_an_electric_generator_in_3d
- generator_in_2d
- e_-_core_transformer
Wide Support for Eigenfrequency Analysis
The Eigenfrequency study is now supported for most of the AC/DC Module interfaces: Electric Currents, Electric Currents in Shells, Electric Currents in Layered Shells, Electrical Circuit, Electrostatics, and Magnetic Fields. In addition to supporting full-wave cavity mode analysis in the Magnetic Fields interface, it is possible to run eigenfrequency analyses with models involving electrical circuits. The eigenfrequency support is primarily developed for the AC/DC Module, but other modules that provide one of the affected physics interfaces will benefit from it too.
New and Enhanced Functionality for the Electrical Circuit Interface
For Time Dependent studies, the Electrical Circuit interface has been equipped with an "event-based" Switch feature. This allows you to model the "instantaneous" on-off switching of certain connections in the circuit. The switch can be current controlled, voltage controlled, or controlled by user-defined Boolean expressions.
Furthermore, Parameterized Subcircuit Definitions are added. Together with the Subcircuit Instance, these allow you to create your own building blocks containing smaller circuits, and use multiple parameterized variants of those in your larger circuit. Finally, the state, event, and solver machinery has been improved, especially the transient modeling of nonlinear (semiconductor) devices, which has become more robust.
The circuit improvements are primarily developed for the AC/DC Module, but other modules that provide access to the Electrical Circuit interface will benefit too. You can view the new functionality in these updated models:
- operational_amplifier_with_capacitive_load
- battery_over_-_discharge_protection_using_shunt_resistances
- p_-_n_diode_circuit
- reverse_recovery_of_a_pin_diode
New Default Plots for the Magnetic Physics Interfaces
New default plots have been developed specifically for physics interfaces that support magnetic fields: Magnetic Fields, Magnetic Fields, No Currents, and the Rotating Machinery, Magnetic multiphysics interface. The magnetic flux density norm is plotted as a multislice or a surface plot, together with streamlines or contours to indicate the field direction. In 2D and 2D axisymmetric models, the streamlines show a divergence-free magnetic field. Whenever possible, a contour plot of the out-of-plane magnetic vector potential is included, which is more exact than the streamlines, in the sense that the contours are closed, and the contour density is directly proportional to the local magnetic flux density. In 3D, the streamlines follow the magnetic field after it has been projected onto the slice planes. The resulting pattern is not necessarily divergence free, but still provides a clear, intuitive indication of what the 3D field will look like. You can view this new plot functionality in the following models:
- inductance_matrix_calculation_of_pcb_coils (new model)
- generator_in_2d
- voltage_induced_in_a_coil_by_a_moving_magnet
- modeling_of_a_3d_inductor
- magnetic_damping_of_vibrating_conducting_solids
- vector_hysteresis_modeling
Ferroelectric Material Model in Electrostatics
For the Charge Conservation feature in the Electrostatics interface, the list of dielectric material models has been extended with a Ferroelectric material option. The ferroelectric material model is the dielectric equivalent of the Jiles Atherton magnetic hysteresis model; instead of a time-varying magnetization, it models a time-varying polarization. You can view this feature in the new Hysteresis in Ferroelectric Material tutorial model.
This material model is the electrostatic part of a new Ferroelectroelasticity multiphysics interface, intended for analysis of ferroelectric materials, which exhibit nonlinear piezoelectric properties. The Ferroelectric material option is included in the AC/DC Module. However, the Ferroelectroelasticity multiphysics interface additionally requires either the MEMS Module or the Structural Mechanics Module.
Magnetic Materials from Bomatec
The AC/DC material library has been extended with magnetic materials from Bomatec. This includes all the NdFeB standard grades ("normal", M, H, SH, UH, EH, AH, BH, /S, M/S, H/S, SH/S, UH/S, EH/S, AH/S, BH/S, H/ST, SH/ST, UH/ST, EH/ST, AH/ST, and BH/ST); NdFeB (bonded, injection molded, and extruded); ferrite (isotropic, anisotropic, and injection molded); SmCo (injection molded); SmFeN (injection molded); SmCo5 grades; Sm2Co17 grades; and AlNiCo (cast and sintered).
The materials include electromagnetic properties — relative permittivity 
, recoil permeability 
, and remanent magnetic flux density norm 
— as well as several properties related to thermal modeling: thermal conductivity, 
; density, 
; and heat capacity at constant pressure 
.
Enhanced Feature: Coil with Slanted Cut
The Coil domain feature (both for the Single Conductor model and the Homogenized Multiturn case) has been equipped with support for a Slanted Cut. The Slanted Cut setting allows you to relax the constraints used for determining the coil geometry (it applies the input/output boundary constraint "on average" rather than locally). Relaxing the constraint is needed for cases where the natural direction of the current (or the wires) is at an angle with respect to the input or output normal. A typical example is a helical coil, where the input/output boundaries represent a periodicity plane — as is the case for twisted three-phase cables, or fully resolved Litz wires or Milliken conductors. You can see this new feature in the updated Cable Tutorial Series tutorial model.
Faster Cable Analysis: New Tutorial Model
The Cable Tutorial series has been updated to demonstrate short-twisted periodicity, a kind of periodicity that allows you to reduce the computational effort required for fully resolved 3D twisted cable models, from hours on large cluster systems to about a minute on a laptop. The logic behind the used periodicity is explained in detail, including cases that involve more than two lay lengths, cables with fully resolved Milliken conductors, stranded screens, or a double armor, for example.
The theory for twisted strands and the use of appropriate meshing follows the latest developments in numerical research, and applies to both large-scale insulated submarine cables and umbilical cables, EV charging cables, fully-resolved Litz wires, and the bare cables used in overhead power lines. Additionally, the series discusses the resistive, capacitive, inductive, and thermal properties of cable systems, as well as different bonding schemes: single-point bonding, solid bonding, and cross bonding. You can see this new feature in the updated Cable Tutorial Series tutorial model.
- For a more in-depth look: Modeling Busbars and Cables in COMSOL Multiphysics®
- For 2D modeling in particular: Modeling Cable Systems in COMSOL
New Tutorial Models
COMSOL Multiphysics® version 5.6 brings several new tutorial models to the AC/DC Module.
Hysteresis in Ferroelectric Material
Application Library Title:
ferroelectric_hysteresis
High-Voltage Insulator
Application Library Title:
high_voltage_insulator
Position Optimization of Grading Rings
Application Library Title:
grading_ring_optimization
Inductance Matrix Calculation of PCB Coils
Application Library Title:
inductance_matrix_pcb_coils