Atualizações do AC/DC Module

Para os usuários do AC/DC Module, COMSOL Multiphysics® a versão 5.3a oferece uma nova interface física chamada Magnetic Fields, No Currents, Boundary Elements; atualizações no pós-processamento da interface Electrostatics, Boundary Elements, lançada previamente; um novo modelo de material para modelagem de ímãs permanentes macios; e uma nova condição de contorno chamada Surface Magnetic Current Density. Veja abaixo os detalhes sobre todas as atualizações do AC/DC Module.

New and Updated Boundary Element Interfaces

A new physics interface has been developed based on the boundary element method (BEM): the Magnetic Fields, No Currents, Boundary Elements interface. It solves for the scalar magnetic potential and can be used as a standalone interface to model permanent magnets with linear, constant, and homogeneous properties. The interface also provides multiphysics coupling features for combining finite element method (FEM) and BEM modeling of more complex scenarios when used together with the finite-element-based Magnetic Fields, No Currents and Magnetic Fields interfaces. For example, hybrid FEM-BEM models can be used to model nonlinear anisotropic magnetic materials based on an FEM formulation with a surrounding domain that utilizes the new Magnetic Fields, No Currents, Boundary Elements interface.

Introduced with COMSOL Multiphysics® version 5.3, the Electrostatics, Boundary Elements interface has been enhanced with support for electrostatic force calculations and new postprocessing variables on boundaries. Additionally, postprocessing and visualization of boundary-element-based fields has been improved with automatic smoothing near boundaries.

A model of a submarine with its magnetic signature below. A submarine with its magnetic signature 1 km below it. The box and submarine have been magnified by a factor of 20 in the plot. In this model, the boundary element method is used to model the open space outside the box, whereas the finite element method is used to model the submarine and its immediate vicinity. A submarine with its magnetic signature 1 km below it. The box and submarine have been magnified by a factor of 20 in the plot. In this model, the boundary element method is used to model the open space outside the box, whereas the finite element method is used to model the submarine and its immediate vicinity.

Updated Interface for Rotating Machinery

The Rotating Machinery, Magnetic interface in the AC/DC Module now uses an updated version of the moving mesh functionality. The moving mesh settings are now shared between physics interfaces, avoiding duplication of settings. This facilitates multiphysics modeling in moving domains with greater ease as compared to previous versions. Among other benefits, this makes it much easier to combine electromagnetics with fluid flow in rotating machinery.

Material Model for Soft Permanent Magnets

A new material model for modeling soft permanent magnets has been added to the Magnetic Fields; Magnetic Fields, No Currents; and Rotating Machinery, Magnetic interfaces. A generic example material Demagnetizable Nonlinear Permanent Magnet with the approximate properties of AlNiCo 5 has been added to the AC/DC material database to serve as a template for user-defined materials supporting the new material model. Two important permanent magnet materials are AlNiCo (soft magnet) and NdBFe (hard magnet). AlNiCo magnets have an advantage over NdBFe magnets at elevated operating temperatures since the Curie temperature for AlNiCo magnets is in the range 700–860°C as opposed to 310–400°C for NdBFe magnets. For this reason, AlNiCo is sometimes used in permanent magnet (PM) motors where temperatures may be too high for NdBFe magnets. A key design consideration for such motors is that the magnetic flux density in the magnets must never drop below the "knee" of the magnetization curve as that would result in irreversible demagnetization and loss of performance.

An example of using the material model for soft permanent magnets, new in COMSOL Multiphysics 5.3a. Soft permanent magnet example: When the flux path of the soft permanent magnet (cylinder) is closed by the iron core (gray), the soft magnetic material stays in the safe region above the knee of its magnetization curve. When moved into free air, it goes below the knee and will not return along the original curve, but instead follow the dotted red line. It will suffer from permanent demagnetization. Soft permanent magnet example: When the flux path of the soft permanent magnet (cylinder) is closed by the iron core (gray), the soft magnetic material stays in the safe region above the knee of its magnetization curve. When moved into free air, it goes below the knee and will not return along the original curve, but instead follow the dotted red line. It will suffer from permanent demagnetization.
 

When moved into free air, the soft permanent magnet loses so much of its initial magnetization that the change becomes irreversible.

Descontinuidade do Potencial Magnético Escalar

Ao construir modelos usando o potencial magnético escalar com a interface Magnetic Fields, No Currents, agora é possível introduzir loops de corrente em arestas através do recurso Magnetic Scalar Potential Discontinuity. Este recurso é disponibilizado quando a opção Advanced Physics Options é ativada e pode resultar em modelos que consomem menos recursos computacionais e são mais eficientes, se comparados à formulação mais geral que usa potencial vetorial.

An example that uses the Magnetic Scalar Potential Discontinuity feature in the AC/DC Module.

Toroid inductor model with the new Magnetic Scalar Potential Discontinuity feature applied on the gray circular boundaries, equivalent to imposing a line current of 1[kA] along the associated circular edges.

Toroid inductor model with the new Magnetic Scalar Potential Discontinuity feature applied on the gray circular boundaries, equivalent to imposing a line current of 1[kA] along the associated circular edges.

Densidade de Corrente Magnética Superficial

Uma densidade de corrente magnética na superfície agora pode ser especificada como um campo vetorial 3D em uma superfície. Com a nova condição de contorno Surface Magnetic Current Density, incluída na interface Magnetic Fields, a densidade de corrente magnética é projetada em uma superfície de contorno, ignorando-se sua componente normal. Isso permite especificar uma densidade de corrente magnética na superfície dos contornos exteriores e interiores do seu modelo. Essa nova condição de contorno foi incluída para situações específicas de modelagem, tais como a modelagem de dipolos elétricos.

Exemplo de Modelagem de Laminados no Domínio do Tempo

O modelo tutorial sobre máquinas rotativas 3D foi atualizado para servir como exemplo de rotor laminado. O cilindro rotativo do modelo é simulado com e sem condições de contorno de isolamento usando a interface Rotating Machinery, Magnetic e os resultados são comparados. Quando o rotor é laminado, os resultados mostram que as perdas por correntes parasitas são reduzidas significativamente.

Visualized results from the Rotating Machinery 3D tutorial model. Rotating machinery example where the cylinder rotates around its axis, generating eddy currents from the magnetic field produced by a permanent magnet. The current density is calculated for two situations: without an insulating layer (top image, left legend) and with an insulating layer (bottom image, right legend). Rotating machinery example where the cylinder rotates around its axis, generating eddy currents from the magnetic field produced by a permanent magnet. The current density is calculated for two situations: without an insulating layer (top image, left legend) and with an insulating layer (bottom image, right legend).


Caminho na Application Library:
ACDC_Module/Motors_and_Actuators/rotating_machinery_3d_tutorial

Modelos para Verificação das Forças Magnéticas

Dois novos modelos tutoriais, nos quais se calcula a força magnética e o torque, foram acrescentados à Application Library. Eles são parte de uma série planejada de tutoriais sobre o uso das interfaces Magnetic Fields, No Currents e Magnetic Fields, No Currents, Boundary Elements. Em ambos os modelos, BEM e FEM são comparados a modelos analíticos. O objetivo dos modelos é servir como uma introdução ao método dos elementos de contorno para magnetoestática.

A model of two parallel magnetized rods.

Two parallel magnetized rods of one meter length, placed one meter apart. The remanent flux density inside the rods is chosen such that the analytical model predicts a repelling force between the two rods of exactly one Newton.

Two parallel magnetized rods of one meter length, placed one meter apart. The remanent flux density inside the rods is chosen such that the analytical model predicts a repelling force between the two rods of exactly one Newton.

Caminho na Application Library:
ACDC_Module/Verification_Examples/force_calculation_02_magnetic_force_bem
ACDC_Module/Verification_Examples/force_calculation_03_magnetic_torque_bem

Modelo Tutorial Atualizado: Lumped Loudspeaker Driver Using Lumped Mechanical System

Este é o modelo de um alto-falante com bobina móvel onde uma analogia de parâmetros concentrados representa o comportamento dos componentes elétricos e mecânicos do alto-falante. Os parâmetros de pequenos sinais servem como entradas do modelo concentrado. Nesse modelo, os componentes mecânicos do alto-falante, tais como a massa móvel e as perdas mecânicas da suspensão, são modelados usando a interface Lumped Mechanical System.

A plot from the Lumped Loudspeaker Driver tutorial model. Pressure field plotted as isosurfaces (above the speaker cone) and as a surface plot (below the speaker cone). Pressure field plotted as isosurfaces (above the speaker cone) and as a surface plot (below the speaker cone).

Caminho na Application Library:
Acoustics_Module/Electroacoustic_Transducers/lumped_loudspeaker_driver_mechanical