The Magnetic Machinery, Rotating, Time Periodic Interface
The Magnetic Machinery, Rotating, Time Periodic (mmtp) interface (), found under the AC/DC>Electromagnetics and Mechanics branch when adding a physics interface, is used for design and analysis of rotating magnetic machines such as electric motors and generators. Time Periodic equation form is enforced, but Stationary, Frequency, and Time Dependent studies are allowed for coupling to other physics. The interface supports 2D and in-plane magnetic fields.
The physics interface solves Maxwell's equations formulated using out-of-plane magnetic vector potential, see The A Formulation, Time Periodic, and Time Periodic Equation.
When this physics interface is added, these default nodes are also added to the Model Builder - Free Space, Exterior Boundaries (the default boundary condition), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, external sources and boundary conditions. You can also right-click Magnetic Machinery, Rotating, Time Periodic to select physics features from the context menu.
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The physics interface only works correctly when modeling rotating machinery if the geometry is created as an assembly pair from individual composite objects for the rotor and stator parts, and proper Rotating Domain and Rotational Continuity Pair features are added. The rules are similar to that of the Rotating Machinery, Magnetic interface. However, each Rotating Domain should also cover exactly one geometry component.
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Rotation features can be specified only if the Motion type setting in the Motion Settings section is set to Rotational motion. The button Add Rotational Boundary Features in that section can be used to simplify the model setup for the most typical geometries.
Settings
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is mmtp.
Thickness
Here, it is possible to enter a value for the Out-of-plane thickness d (SI unit: m). The default value is 1 m and affects lumped quantities such as axial torques, forces, and voltages.
Time periodic Settings
Here, it is possible to enter values for the following inputs:
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Time periodic electrical frequency fTP (SI unit: Hz). The default value is 50 Hz, but it is possible to enter a different value or to have the frequency valued to freq if this variable is supplied by the study, as it is when having frequency domain study steps.
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Number of time frames nTP, which is an even integer that must be equal to or larger than 2. This specifies the number of points that are used to discretize the time period (or in other words, the phase interval ϕ ∈ [0, 2π]). Here, ϕ is an independent variable that can be accessed in user inputs as ϕTP = ϕ by using the expression <phystag>.phaseTP (for example, mmtp.phaseTP). For more details, see Feature Specific Variables and Accessing the Solution at Different Phases. The Number of time frames is also accessible as a variable named <phystag>.nTP (for example, mmtp.nTP).
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Number of variable groups, which is a setting that is useful for decreasing RAM consumption, as it simplifies the setup of segregated solver strategies. The Number of variable groups is 1 if Dependent variable grouping is set to Merge all variables (the default), 2 if it is set to Two groups, and nTP if it is set to One variable per group. Otherwise, the Number of variable groups setting can also be set to User defined.
Motion Settings
This section specifies the type of motion used in the model.
The Motion type can be either No motion or Rotational motion (the default). If Rotational motion is specified, it is possible to use feature that are specific for rotating machines, and it is possible to use the Number of poles npoles input in order to synchronize different settings with each other. In particular, this input enables synchronization of periodicity information between different nodes that are needed when just a sector of a full machine is modeled. For more information, see Typical Setup of Rotating Domain, Rotational Continuity Pair, and Rotational Periodicity.
Discretization
Select the shape order for the Magnetic vector potential dependent variable — Linear, Quadratic, Cubic, Linear serendipity (the default), Quadratic serendipity, or Cubic serendipity. For more information about the Discretization section, see Settings for the Discretization Sections in the COMSOL Multiphysics Reference Manual.
Domain, Boundary, Edge, Point, and Pair Nodes for the Magnetic Machinery, Rotating, Time Periodic Interface
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Permanent Magnet Motor with Campbell Diagram: Application Library path ACDC_Module/Devices,_Motors_and_Generators/pm_motor_2d_campbell_diagram