You can apply boundary conditions and loads to a harmonic magnetic analysis either on the solid model (keypoints, lines, and areas) or on the finite element model (nodes and elements). To apply boundary conditions and loads to a 2D harmonic analysis, use the same GUI paths and macros described for a 2D static analysis in 2D Static Magnetic Analysis
For a harmonic magnetic analysis, you can specify three types of load step options: dynamic, general, and output controls. Alternative Analysis Options and Solution Methods describes these load step options.
For static analyses, use the cyclic symmetry capability to define periodic boundary conditions. For harmonic or transient analyses, use the PERBC2D macro.
Using the PERBC2D macro, you can define periodic boundary conditions automatically for a 2D analysis. PERBC2D writes constraint equations or assigns node coupling necessary for two periodic symmetry planes. To invoke the macro, use either of the following:
Electric and Magnetic Macros discusses and illustrates options for using PERBC2D.
By definition, a harmonic analysis assumes that any applied load varies harmonically (sinusoidally) with time. Specifying a harmonic load completely usually requires three pieces of information: the amplitude (zero to peak value), the phase angle, and the operating frequency.
Phase angle measures the time by which the load lags (or leads) a frame of reference. On the complex plane (see Figure 3.2: Relationship Between Real / Imaginary Components and Amplitude / Phase Angle), phase angle is the angle measures from the real axis. The phase angle is required only if you have multiple loads that are out-of-phase with each other (for instance, in three-phase analysis).
For out-of-phase current densities or voltages, use the PHASE field on the
BF, BFE, or BFK
commands (or their equivalent menu paths) to specify the phase angle in degrees.
For out-of-phase potentials or current segments, use the
VALUE and VALUE2
fields on the appropriate load commands or menu paths to specify the real and
imaginary components of the complex loads. Figure 3.2: Relationship Between Real / Imaginary Components and Amplitude / Phase
Angle shows
how to calculate the real and imaginary components.
This is the frequency of the alternating current (in Hz). You specify it as a load step option via either method shown below:
To apply source current density (JS) as a load directly to the elements of a stranded conductor, you can use either of the following:
Alternatively, you can apply source current densities to areas of the solid model by using the BFA command. You can then transfer the specified source current densities from the solid model to the finite element model by using either the BFTRAN command or the SBCTRAN command.
Current (AMPS) is a nodal current load that applies only to massive (solid) conductor regions with an impressed current. In 2D for the PLANE13 and PLANE233 elements, this load requires the AZ-VOLT degree of freedom set in the conductor region. Current represents the total measurable current flow through the conductor (units of current), and you can apply it only to 2D planar and axisymmetric models.
To apply a uniform current load through a cross-section of the skin-effect region, you must couple the VOLT degree of freedom across that cross-section. To do so, use either of the following:
In 2D planar or axisymmetric models, select all nodes in the skin-effect region and couple their VOLT DOFs. Then, apply the current at one node in the cross-section, using one of the following:
Infinite surface flags are not actual loads, but they are used to indicate which surface of an infinite element faces toward the open (infinite) domain. Applying the INF label to an element face turns the flag on for that face.
Maxwell surface flags are not actual loads, but they are used to indicate on which element faces the magnetic force distribution is to be calculated. Applying the MXWF label to an element face turns the flag on for that face.
Typically, you turn the MXWF flag on for the surfaces of air elements adjacent to an air-iron interface. Forces are calculated at the air-iron interface (using the Maxwell stress tensor approach) and stored in the air elements. In POST1, you can review and sum the stored forces in each air element to get the total force acting on the body. You may, if you wish, then use these forces as loads in a structural analysis.
You can specify more than one component, but the components must not share adjacent air elements. (Sharing air elements is typical when a single element layer separates two components.)
When using PLANE233, you do not need to apply any force flags to calculate magnetic forces. For more information, see Older vs. Current 2D Magnetic Element Technologies.
Magnetic virtual displacement flags are not actual loads, but they are used to initiate the calculation of forces on a body in the model. The MVDI method provides an alternative to the Maxwell surface (MXWF) method. The program calculates the forces, using the virtual work approach, as it processes the solution.
To trigger the calculation, specify the MVDI flag value as 1.0 at all nodes in the region of interest and 0.0 (default setting) at all adjacent air nodes. Although you can enter MVDI values greater than 1.0, you should not normally do so. Forces will be calculated and stored in the air elements adjacent to the body.
The band of air elements surrounding the region of interest should be uniformly thick. In POST1, you can review and sum the stored forces in each air element to get the total force.
For information on calculating magnetic forces when using PLANE233, see Older vs. Current 2D Magnetic Element Technologies.