2. Introducing the new functions
2-1. High speed solver
This section introduces two functions which can lead to reduced analysis time either through faster processing or by reducing a transient period.
2-1-1. Time period explicit error correction method
The time period explicit error correction method uses the temporal periodicity of the varying field in the magnetic field analysis. It shortens the transient period that occurs in a transient analysis, and forces the model into steady state operation in fewer time steps than if the model were allowed to achieve steady state operation on its own. This function is effective for models with an electric potential (voltage) source for circuits. It is also effective for models that require substantial analysis time (analysis steps) before reaching steady state. JMAG's unique technology has been built into this function, so it can be applied to almost all problems with time varying fields.
As an example, an induction motor analysis could require up to 10 time periods before transitioning to steady state operation. If the goal is to observe steady state operation, then these 10 periods are not necessary. In this case, adopting the time period control method would facilitate a reduction in analysis by reducing the transient period (fig. 1).
It is possible to reduce analysis time even further by combining the time period method with the traditional approximate steady state method.
Fig. 1: A comparison of steady torque convergence when applying
and not applying the time period explicit error correction method in
induction motor analysis.
A second example of the time period method involves the analysis of a transformer for a switching power supply. In this case the capacitance of the secondary smoothing capacitor determines the system's time constant. This could lead to an extremely large time constant and thus a long analysis time before reaching steady state operation. By using the time period explicit error correction method, it is possible to considerably shorten the analysis time (fig. 2).
Fig. 2: Time period explicit error correction method in analysis of a
transformer for switching power supply
A comparison of convergence for steady current when
applying and not applying the method.
2-1-2. GPU support
Over the last few years there has been a great deal of improvements in the performance of a video card's GPU (Graphic Processing Unit). The GPU is now powerful enough that it can be incorporated into the solver.
JMAG is also working on faster calculations via parallel computing by using the computer's GPUs in the magnetic field analysis. This function can also be combined with the existing parallel processing licenses (SMP).
(Caution 1) This function is only provided to users that request it. Furthermore, there is a restriction on the GPUs that are compatible with this feature, so when using it refer to the operating environment at the bottom of the following link:
2-2. Improvement in the geometry editor
We have made improvements to many features in the Geometry Editor, including handling of basic shapes, creating skew geometry, and generating manual meshes. The following sections will introduce some improvements in constraint functions and skew extrusion. These functions are introduced with the goal of improving accuracy and productivity for designers.
2-2-1. Improvement in constraint functions
Correctly constraining a model is a necessary step when creating its geometry. This is especially true for parametric analyses where the geometry can be driven by a design table.
One big improvement is that the constraints in the geometry editor are compatible with JMAG-Express (the motor template has been replaced by JMAG-Express). This means that there is no need to reset constraints when transferring data from JMAG-Express to JMAG-Designer. It also means that turning a 2D model from JMAG-Express into a 3D model in JMAG-Designer is much easier. Constraint information from a JMAG-Designer model is transferred to JMAG-Express, which makes creating a template in JMAG-Express much less rigorous.
Additionally, Ver. 11 now supports radius and diameter constraints as well as dependent constraints. Having dependent constraints means that constraints can be grouped together and handled as a single parameter. This will make parametric condition settings substantially easier than in previous JMAG versions (fig. 3).
Fig. 3: Changes in geometry that use a group setting of several constraints
2-2-2. Skew extrusion
It is sometimes necessary to skew a rotor in order to reduce cogging torque. Unfortunately, accurately evaluating the skew effects requires a 3D analysis.
The skew extrusion feature allows users to easily create a skewed 3D geometry. The skew is applied in the geometry editor, which performs a skewed extrusion on the 2D sketch (fig. 4). Creating a skewed geometry is also possible for regions where a mesh has been generated.
Fig. 4: An example of creating geometry with the skew extrusion function
It considers the skew in the rotor of the induction motor
2-3. Mesh generation functions
We have improved the efficiency of mesh generation with the introduction of a new algorithm in the mesh generator.
2-3-1. Extruded mesh
When using the automatic mesh function to generate a mesh in a rotating machine, there are times when the divisions in the axial direction are finer than necessary.
This is not a problem with a manual mesh since the number of axial divisions is directly controlled, but this type of control was not possible with the automatic mesh until now. The extruded mesh uses a prism mesh to ensure a highly accurate analysis even though the number of elements has been reduced (fig. 5). This function can be applied to a motor with a skewed geometry, as well.
Fig. 5: A comparison of a traditional mesh model (left) and an extruded mesh model (right)
2-4. Improvement in JMAG-Designer's performance
JMAG-Designer's main characteristic is that it can handle several models or studies in a single project. By using the parametric analysis function, it is possible to calculate multiple cases with various design variables as parameters. These are useful functions, but we have heard many requests to reduce the time required to switch between studies and to increase the number of parametric studies available. These two issues have been addressed in Ver. 11.
2-4-1. Faster multi-model and multi-case processing
In JMAG-Designer Ver.11, we shortened the time necessary for switching between study displays and raised the upper limit for the number of cases that can be generated in a parametric analysis. It is also now possible to draw response graphs for multiple cases in parametric analysis.
A comparison of the time necessary to import multiple cases and switch between cases for Ver.10.5 and Ver.11 is shown (fig. 6).
Fig. 6: A multi-case importing time comparison (left) and a switching display time comparison (right)
The comparative verification was a 7700 element 2D model, and there were 225 cases.
Ver. 11 also has multiple improvements to its multiphysics capabilities. The following section introduces these new features.
2-5-1. Coupled magnetic field and structural analysis including a structural displacement
With JMAG's coupled magnetic field and structural analysis function, it is possible to simulate displacement and stress in a structural analysis based on the electromagnetic force from a magnetic field analysis. It is also possible for a magnetic analysis to simulate the magnetic flux density and iron losses, including the effects of stress based on a structural analysis. However, it is not possible to do a magnetic field analysis if a plastic deformation is involved in the structural analysis.
It is also now possible to do a magnetic field analysis that applies the displacement predicted in a structural analysis. This is possible with the use of a new coupled magnetic field and structural analysis tool. The targeted structural analysis solver becomes the structural analysis (DS) module of JMAG and Abaqus (developed by SIMULIA).
One-way coupling with DS is can facilitate the magnetic analysis of a model with static plastic deformation where a change in a flux path affects the magnetic circuit. For example, variation in a stator's inner diameter caused by shrink fitting or press fitting the motor's case can influence the motor's characteristics. Changes in the circumferential air gap length due to variations in the stator's inner diameter can alter the motor's flux path, which then affects cogging torque. Coupling the magnetic analysis to the structural analysis makes it is possible to gain an understanding of this fluctuation.
Two-way coupling with Abaqus is useful for analyses of electromagnetic phenomena that include a plastic deformation which changes at each step. For example, evaluating the temperature distribution of a part that is undergoing induction heating will have losses and heat generation that are affected by changes in the flux path from plastic deformation. In a coupled analysis, it is possible to account for those kinds of phenomena and evaluate the results of the induction heating process (fig. 7).
Fig. 7: Two-way coupled magnetic field and structural analysis that accounts for press fabrication of the part.
2-6. Coupled Analysis
Many customers have modeling programs that they are familiar with, and have requested to use these programs in conjunction with JMAG. JMAG already has links to many packages, but these do not cover all of the programs available.
JMAG now includes an open interface program called MpCCI (Multi-Physics Code Coupling Interface). This program can correctly map physical quantities between programs that do not have a direct link. This tool will extend modeling capabilities even further.
2-6-1. General interface support for coupled analysis
We have implemented an interface in JMAG-Designer Ver.11 that supports MpCCI. Fig. 8 shows the steps for an analysis using MpCCI, and another software program.
Fig. 8: The steps for a coupled analysis with JMAG, which uses MpCCI, and another CAE.
2-7. Result processing
Extracting results is necessary when examining specific parameters. JMAG-Designer Ver.11, has a results extraction tool that allows you to extract the objective result without starting JMAG-Designer or JMAG-RT Viewer.
2-7-1. Efficiency maps
An efficiency map is a vital characteristic diagram that allows you to understand a motor's characteristics at a glance. The efficiency map plots the interaction of the current amplitude and phase angle at various rotation speeds and torques across the controller range. The resulting motor efficiency is very useful, but it requires a great deal of time and effort.
JMAG-RT Viewer allows you to draw a speed versus torque curve and an efficiency map with one click after you have set the control method and drive type (fig. 9).
Fig. 9: An efficiency map using JMAG-RT Viewer
2-8. New solutions
JSOL is always working to extend and improve the capabilities of JMAG-Designer. Two new tools set for release later this year, JMAG-VTB and JMAG-SuperExpress, seek to dramatically reduce the time necessary to set up complex studies.
The goal of JMAG is to act as a Virtual Test Bench and reproduce all of the measurements taken on a physical test bench. This sounds like a difficult task, but JMAG continues to reach for this ideal.
Many functions are being developed for future simulations, with the goal of further improving capabilities through coupling and linking. The downside of this development is that increasing capabilities results in a great deal of information to remember in order to master so many functions. The procedures will continue to grow more complex as simulations work to incorporate more diverse phenomena.
JMAG VTB seeks to reduce the amount of settings that a user must create for each model analysis. By selecting the object that you want to analyze and selecting the analysis objective, the necessary calculations run. This can be thought of as automating the analysis so that once you have set the work flow; you can apply it to all new models. With the initial version, we are planning on releasing it with approximately 20 workflows.
The workflows include built in settings, such as the necessary mesh division parameters, rotation angle, and graph displays. Our users can obtain results by simply importing the model data and setting the goal of the simulation. JMAG-VTB also has search functions for calculations and models that were carried out in the past, so the system allows you to reuse models easily. (fig. 10).
Fig. 10: Analysis automation via JMAG-VTB
We will release JMAG-SuperExpress, which is equipped with calculation functions for the motor templates.
SuperExpress provides detailed motor analyses of basic parameters through the use of FEA. Calculations for cogging torque, iron loss distribution, inductance maps, and efficiency maps are also possible (fig. 11).
Fig. 11: A screen image of JMAG-SuperExpress
We will introduce the details of the functions in April's JMAG Newsletter.
3. In closing
JMAG-Designer is continuously improving to ensure that users can perform simulations accurately and quickly with a less difficultly.
Examples of the functions introduced here can be seen in the application notes section on the JMAG website. If you have any questions about how to use the new functions, please contact your support representative.