Most of the tasks you perform to solve a 2D harmonic magnetic analysis are the same as the tasks described in 2D Static Magnetic Analysis for solving a 2D static magnetic analysis. The main differences are that you specify a different analysis type and that the harmonic analysis yields different results that may require different postprocessing methods.
To specify the analysis type, do either of the following:
In the GUI, choose menu path and then choose a Harmonic analysis.
If this is a new analysis, issue the command ANTYPE,HARMIC,NEW.
If you want to restart a previous analysis (for example, to restart an unconverged solution or to specify additional excitation), issue the command ANTYPE,HARMIC,REST. You can restart an analysis only if you previously completed a harmonic magnetic analysis, and the files Jobname.emat, Jobname.esav, and Jobname.db from the previous run are available.
You can use the following "Full" method to solve harmonic electromagnetic problems. It is the default method.
First, define the solution method, using either of the following:
Next, define how the harmonic degree of freedom solution is listed in the printed output (the Jobname.out file). You can choose either real and imaginary parts (default) or amplitudes and phase angles. This option is used mainly with circuit-coupled problems using the CURR and EMF degrees of freedom. To specify the solution listing format, use either of the following:
You can choose the sparse direct (SPARSE) solver (default), the Jacobi Conjugate Gradient (JCG) solver, or the Incomplete Cholesky Conjugate Gradient (ICCG) solver.
To select an equation solver, use either of the following:
Note: You must "OK" the dialog box containing the HROPT and HROUT commands to reach the equation solver dialog box.
For nonlinear problems, the program continues to do equilibrium iterations until the convergence criteria are satisfied (or until the maximum number of equilibrium equations is reached.
To specify the convergence criteria, use either of the following:
You can either use the default convergence criteria or define custom criteria.
Default Convergence Criteria
By default, the program checks for degree of freedom (AZ, VOLT, EMF) convergence by comparing the square root sum of the squares (SRSS) of the degree of freedom imbalances against the product of
VALUEXTOLER. The default value ofVALUEis based upon the selected NORM and the current total DOF value (program chosen), orMINREF, whichever is greater. In general, you do not setMINREF. The default value ofTOLERis 0.001.For degrees of freedom, the program bases convergence checking on the change in degree of freedom (Δu) between the current (i) and the previous (i-1) iterations: Δu = ui-ui-1.
Custom Convergence Criteria
You can define custom convergence criteria, instead of using the default values.
Using tighter convergence criteria improves the accuracy of your results, but at the cost of more equilibrium iterations. If you want to tighten (or loosen) your criteria, you change the
TOLERby one or two orders of magnitude. In general, you continue to use the default value ofVALUE; that is, change the convergence criteria by adjustingTOLER, notVALUE.
For most electromagnetic problems only a single frequency is used. You set the frequency (in Hz), using either of the following:
You can input a single frequency in either the FREQB or
FREQE field.
You can specify the number of harmonic solutions to be calculated. The solutions (or substeps) are evenly spaced within the specified frequency range. For example, if you specify 10 solutions in the range 30 to 40 Hz, the program calculates the response at 31, 32, 33, ..., 39, and 40 Hz. No response is calculated at the lower end of the frequency range.
To specify the number of harmonic solutions, use either of the following:
You can specify whether the excitations are stepped or ramped. By default, they are ramped, that is, excitation amplitude is gradually increased with each substep. By stepping the excitations, the same excitation amplitude is maintained for all substeps in the frequency range. For electromagnetic problems excitations are normally stepped. The ramp option is useful for converging nonlinear problems at a single frequency.
To specify whether the excitations are stepped or ramped, use either of the following:
You can specify the number of equilibrium iterations performed for a nonlinear harmonic analysis at each frequency. The default is 25. It is recommended that the number of equilibrium iterations be set to 50 or higher to ensure convergence.
To specify the number of equilibrium iterations, use either of the following:
You can set output control options.
An option enables you to include any results data in the printed output file (Jobname.out). To control printed output, use either of the following:
Another option controls what data goes to the results file (Jobname.rth). To control database and results file output, use either of the following:
Use the SAVE_DB button on the toolbar to save a backup copy of the database. To retrieve a model, re-enter the program and use one of the following:
For linear problems you can initiate a solution using either of the following:
For a nonlinear analysis, a two-step solution sequence at each frequency is recommended to ensure convergence:
Ramp the excitation over three to five substeps, each with one equilibrium iteration.
To specify a ramped or stepped excitation, you use either of the following:
Command(s): KBCGUI:To specify three to five substeps, use either of the following:
Command(s): NSUBSTGUI:To specify one equilibrium iteration, use the following:
Command(s): NEQITGUI:To initiate a solution, use either of the following:
Command(s): SOLVEGUI:Calculate the final solution over one substep, with up to 50 equilibrium iterations.
To specify one substep, use either of the following:
Command(s): NSUBSTGUI:To specify up to 50 equilibrium iterations, use either of the following:
Command(s): NEQITGUI:To define custom convergence criteria, instead of using the default values, use either of the following:
Command(s): CNVTOLGUI:
To initiate a solution, use either of the following:
Command(s): SOLVEGUI:
As nonlinear electromagnetic analysis proceeds, the program computes convergence norms with corresponding convergence criteria each equilibrium iteration. Available in both batch and interactive sessions, the Graphical Solution Tracking (GST) feature displays the computed convergence norms and criteria while the solution is in process. By default, /GST is ON for interactive sessions and OFF for batch runs. To turn /GST on or off, use either of the following:
Figure 3.4: Convergence Norms Displayed by the Graphical Solution Tracking (GST) Feature shows a typical GST display:
