JMAG Newsletter January,2013Product Report

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Introducing JMAG-Designer Ver.12

We released JMAG-Designer Ver.12 in December, 2012.
In this report, the people in charge of various new functions introduce important points for your attention.

Overview

We have been working day after day on development to allow users to accurately grasp complex physical phenomena and obtain results via a few operations and without any confusion. The result is JMAG Designer Ver.12, which we released in December, 2012.
Details of how to use the software will be presented at Upgrade Seminars and other events. This report contains messages from the people in charge of developing the new functions.

  • Simulation Engine
    JMAG endeavors to provide fast and stable solvers and meshers. In Ver.12, we have released an expanded slide mesh that provides proper GPU support and mesh with a greater degree of freedom and precision.

  • Physical Modeling
    Detailed modeling is necessary to carry out accurate analyses, but there are limits to how much time can be spent on modeling. JMAG provides modeling functions that allow both high accuracy and high speed. Ver.12's release includes support for magnetostriction, as well as eddy current loss calculation functionality for laminated steel sheet. It also supports coil end modeling functions and harmonic current input for calculation of stray load loss.

  • Results Analysis
    Designs become more reliable as simulation can be done with more combinations of design parameters. We are always working toward better functionality for analyzing results in JMAG, and in Ver.11, we improved its efficiency map and parametric analysis functions. For Ver.12, we have added optimization functions, evaluation of differences between results, and functions for harmonic analysis.

  • Easier to Use
    JMAG is a general-purpose simulation tool primarily for electromagnetic field analysis. It includes a large number of superior functions to enable better simulation. However, most designers who use JMAG need it for certain types of analysis.
    Because of this, JMAG includes JMAG-Express, aimed particularly at motor designers. Ver.12 adds synchronous reluctance motor (SRM) support to the previously-supported permanent magnet synchronous motor (PMSM) and induction motor (IM).
    We have also released JMAG-VTB Ver.2.0 with a new interface to be used as a dedicated system by users other than motor designers as well.

Now, we'll take a look at each of these functions.

Simulation Engine

GPU Support

In recent years, graphics processing units (GPUs), which are hardware for high-speed graphics processing, have been receiving greater attention.
For this reason, JMAG began supporting GPUs at an early stage. In Ver.12, it is now possible to use multiple GPUs in parallel.
Fig. 1 shows one example of a comparison between CPU and GPU calculation times. In this example, using one GPU board leads to a near-doubling of calculation speed over four CPU cores. As for multiple GPUs, calculation time is reduced with every GPU board that is added.
We intend to continue making even greater improvements in processing speed, particularly with multiple GPUs, in the future.

(Masahiko Miwa)

Fig. 1 GPU used for a hybrid stepper motor
Fig. 1 GPU used for a hybrid stepper motor

Computer Used: CPU: Intel(R) Xeon(R) X5672@3.2GHz
GPU: Tesla C2070
* Evaluation of calculation time for solution-finding only.
   Time for building equations and file I/O not included.

Expanded Slide Mesh

To create the mesh for 3D analysis of a rotating machine, JMAG provides both a slide mesh function and a function to create mesh at each step (patch mesh). The slide mesh function allows greater analysis accuracy than the patch mesh function, but in the past there have been limits to the geometries on which it can be used. For this reason, it was necessary to use the patch mesh function when running analyses on a rotating machine with a case or on an axial gap machine.
In Ver.12, we have developed an expanded slide mesh function that allows accurate analysis of these types of machine. This function combines the slide mesh and patch mesh functions. Therefore, by applying a slide mesh to the air gap areas that are vital for precise analysis, and creating mesh with each analysis step for the other air regions, more accurate analysis can be achieved (Fig. 2).
This is one result of the high-precision technology development for rotating machines that we are working on for JMAG. Please try using this for any rotating machine models that you used to analyze with the patch mesh function.

(Kensuke Matsunaga)

Fig. 2 Using the expanded slide mesh
Fig. 2 Using the expanded slide mesh

Physical Modeling

Support for Magnetostriction

Magnetostriction is generated when magnetic flux flows in magnetic steel sheet. Although the changes to a geometry due to magnetostriction are subtle, the effects they can have on electrical devices are not necessarily so minor. For example, magnetostriction is a major cause of vibration and noise in a power transformer. Therefore, it is important to estimate noise and vibration caused by magnetostriction at the design stage.
In Ver.12, it is now possible to run a structural/vibration analysis taking magnetostriction into account. Based on the magnetic flux density obtained from magnetic field analysis, and taking magnetostriction properties into account, the virtual force that produces magnetostriction is calculated as the magnetostrictive force (the left side of Fig. 3). The force calculated in this manner is treated as an input load in JMAG's structural/vibration analysis, the same as the usual electromagnetic force. Magnetostrictive force can also be used in other structural analysis software via electromagnetic force settings tools.
The right side of Fig. 3 shows the displacement due to magnetostriction in a transformer core, with the right and left legs clearly expanding from the magnetostriction. Even when it is not possible to prototype power transformers and the like, the effects of magnetostriction can be estimated using this function.
By paying attention to the various problems that arise from electromagnetic phenomena, such as vibration and noise due to magnetostriction, JMAG robustly supports the design of electric devices.

(Kensuke Matsunaga)

Fig. 3 Magnetostrictive vibration in a transformer core
Fig. 3 Magnetostrictive vibration in a transformer core

Eddy Current Loss Calculation for Laminated Steel Sheet

With higher voltages being used in rotating machines, transformers, etc., the eddy currents generated inside laminated steel sheet have become a problem in recent years. Up to now, it has been necessary to create an extremely fine mesh during simulation for each layer of laminated steel sheet and run a 3D analysis in order to accurately estimate the loss in steel sheet. To solve this problem, we have made it possible to use simple settings to consider eddy currents inside steel sheet in electromagnetic field analysis.
In order to allow evaluation of loss in the laminated core of a motor or transformer, a rough mesh is generated for the core, which is treated as one solid mass in 3D analysis, and the analysis can then be run taking the eddy currents in each steel sheet lamination into account (Fig. 4). Analysis considering eddy currents in steel sheet can also be done with 2D analysis. For example, the eddy current density distribution in a toroidal coil model, which used to be obtained with 3D analysis, can now be gotten via 2D analysis.
Here is an example of the use of this function in a 2D rotating machine analysis. A reduction in output torque corresponding to generated loss can be observed by using this function to consider lamination loss. In this example, the result is an average 8% reduction in torque (Fig. 5). We have also applied the harmonic current input function mentioned above to the current power in order to take harmonics into account.
Because an already-existing 2D model can be used without alterations, settings are extremely simple. We hope this feature will be useful for anyone who has wanted to know the loss in lamination, but found it too much trouble to create a 3D mesh.

(Kazuki Semba)

Fig. 4 Eddy current distribution in laminated steel sheet
Fig. 4 Eddy current distribution in laminated steel sheet


Fig. 5 Reduction in torque due to loss in a 2D motor
Fig. 5 Reduction in torque due to loss in a 2D motor

Coil End Modeling Functions

How can winding geometries be modeled to include their coil ends? In order to accurately grasp physical phenomena such as stray load loss, the effects of coil ends cannot be ignored. However, there are surely many people who have had bad experiences due to the need for complicated sweep lines in creating CAD for coil end geometries.
With the new coil template functionality in JMAG-Designer Ver.12, it is no longer necessary to define these complicated sweep lines. You can now create complex winding geometries including coil ends simply by entering parameters such as number of slots and pitch. Furthermore, not only can you model entire winding geometries with the coil template function, but you can also smoothly connect just the ends to models of coils that you have already created (Fig. 6). We hope you will try using this function.
Coil templates in Ver.12 are our first foray into geometry templates. In the future, we plan to add many more different types of geometry template, not limited to winding geometries. Please watch out for more geometry templates coming soon.

(Yuya Yamashita)

Fig. 6 Coil end modeling using coil templates
Fig. 6 Coil end modeling using coil templates

Harmonic Current Input

Settings for harmonic current have now become easier in electromagnetic field analysis. High-order vibration and phase can now be set in an instant, based on data that has been set for the fundamental wave current.
Recently, there have been more and more instances of harmonics occurring in drive current due to pulse-width modulation (PWM), increased rotation speed of rotating machines, and other reasons. This has made it more important to estimate the effects of harmonic current in electromagnetic field analysis. For example, in current waveform control, adding harmonics to the fundamental wave can greatly change output. By using this function, it is easy to evaluate the effects of any harmonic order.
Also, in the past evaluating harmonic iron loss was made more difficult because noise created during actual measurement was often carried over into harmonic current. With this new function, it is easy to run a harmonic analysis on the current waveform from actual measurements and generate a current waveform using only the frequency components thought to be the main cause.
We hope this feature will be useful for anyone who wants to easily estimate harmonic effects using electromagnetic field analysis.

(Kazuki Semba)

Fig. 7 Harmonic current input
Fig. 7 Harmonic current input

Multi-Purpose File Export

Demands in product design are constantly being raised. For the design of electrical devices, fulfilling electromagnetic demands is necessary of course, but there are also thermal demands and demands in terms of vibration and noise. In order to meet all of these in a timely fashion, electromagnetic design must be carried out in parallel with thermal and mechanical design.
In order to support solutions to development issues, a "Multi-Purpose File Export Tool" has now been developed for JMAG (Fig. 8). With this function, high-precision electromagnetic force distributions, heat generation distributions, and others obtained in JMAG can easily be used in other software.
Highly accurate analysis results (physical quantity distributions) from JMAG are exported in the Nastran file format. This is a highly general-purpose file format, and it can be imported by most software.

  • Analysis results obtained in JMAG are mapped onto mesh models created in other companies' software. There is no need to employ separate mapping tools. Nastran, Abaqus, and ANSYS file formats are supported.
  • Physical quantities obtained in JMAG analysis can be exported. Export can be done with processing by average over time, average over segment, FFT, etc.

Based on JMAG's open-interface concept, we have made efforts to improve its linking with other software. Added to the previous linking with Abaqus and LMS-Virtual.Lab, this new function helps to make analysis results even more useful.

(Yoshiyuki Sakashita)

Fig. 8 The Multi-Purpose File Export dialog box
Fig. 8 The Multi-Purpose File Export dialog box

Results Analysis

Optimization

Ver.12 adds automatic optimization capabilities to the parametric system in JMAG-Designer. The existing parametric function allowed a design to be explored by creating many different cases, however, it was necessary to create all the cases manually. The new function starts from a single case and automatically creates new cases to optimize the design according to user specified criteria. JMAG-Designer uses the response surface method for the optimization and does not require the user to write any scripts.
To enable the optimization function we have also updated the parametric analysis functions, adding new capabilities.

  • A new table to display response data and parameters in a single dialog so results can easily be compared
  • New integral functions to calculate response data from element data, for example maximum flux density in a region.
  • New response data calculations for finding ripple and range.

Fig. 9 Optimization of an actuator
Fig. 9 Optimization of an actuator

Calculation Tools

New tools for analyzing the results have been added in Ver.12. Two calculation tools are available from a new folder in the treeview.

FFT - Fourier Transform for Contour Results

The FFT tool allows you to perform a Fourier transform on time domain results and then display contours of the harmonic components. For example, the results from a time domain simulation of a motor can be transformed into the frequency domain and the flux contours at the harmonic frequencies displayed.

Difference Calculator

When comparing the results from different designs or materials JMAG-Designer could display the results side-by-side but it is still difficult to see small changes. To make the comparison easier, we have added a difference tool which calculates the difference between two results and can display a contour plot of the difference. JMAG's mapping technology is used to allow the difference between results on different meshes to be displayed.

(David Dibben)

Fig. 10 Effects of differences in magnet arrangement and flux barriers on magnetic flux density distribution in stator
Fig. 10 Effects of differences in magnet arrangement and flux
barriers on magnetic flux density distribution in stator

Easier to Use

JMAG-Express

JMAG-Express is a design tool that allows you to perform motor design and evaluation by simply entering parameters such as geometry, winding, and rotation speed, following a template. High-precision results are obtained thanks to its use of the Finite Element Method (FEM).

Fig. 11 Analysis of a switched reluctance motor in JMAG-Express (left: settings dialog, right: analysis results)
Fig. 11 Analysis of a switched reluctance motor in JMAG-Express
(left: settings dialog, right: analysis results)

In Ver.11.1, precision analysis using FEM was limited to permanent magnet synchronous motors, but here I would like to introduce the analysis contents of our newly-added support for induction motors and switched reluctance motors, which have been proposed as substitute candidates for permanent magnet motors.
Switched reluctance motors have a high degree of nonlinearity, making it difficult to predict properties such as inductance and linkage flux. Also, it is essential to ascertain torque ripple in order to find ways of reducing their tendency to produce vibration and noise. In JMAG-Express, the following evaluations are possible (Fig. 11):

  • Psi-I characteristics
  • Static characteristics
  • Drive characteristics
  • Torque ripple

Due to efficiency standards, it may become necessary to reevaluate earlier designs for induction motors. In JMAG-Express, the following evaluations are possible:

  • Circuit parameter
  • Drive characteristics
  • Torque characteristics
  • Line start

We hope you will try JMAG-Express for these situations.

JMAG-SuperExpress's name has been changed to JMAG-Express.

JMAG-VTB

As electrical devices become more complex, more detailed analysis of physical phenomena is needed at the same time that less time is being spent on analysis due to shorter development times and cost reductions. JMAG-VTB was created as a next-generation analysis tool for making "complicated analysis simple" in order to help engineers struggling with these issues. Here, I will briefly explain how complicated analysis can be done more easily.
In order to accomplish complex analysis such as multiphysics, it is necessary to create analysis models for each physical phenomenon, and then carry out calculations linked in the correct order. JMAG-VTB has analysis steps stored as existing procedures, so a user needs only to click a button to get results. In order to obtain the target results, there is no need for confusion about which coupled analyses should be run, what order calculations should go in, and so on. (Fig. 12).
Further, in any kind of analysis, it is necessary to set parameters such as geometry, materials, conditions, mesh, and results processing when creating analysis models. Since some of these parameters are dependent on geometry, they must be converted to values appropriate to the analysis target. JMAG-VTB already contains analysis know-how for different analysis objectives, so appropriate parameters are automatically set for the geometry provided by the user. Even beginners to analysis will not be brought up short by what kind of mesh to generate, how to consider values for step conditions, etc.
Please give JMAG-VTB a try for these situations.

Fig. 12 JMAG-VTB's start-up screen, dashboard, and workflow
Fig. 12 JMAG-VTB's start-up screen, dashboard, and workflow

(Mayumi Warita)

In Closing

So, what do you think? There are still many more features that unfortunately could not be covered in this report. We are now conducting JMAG Upgrade Seminars and special seminars to introduce various functions. We hope JMAG's newest features will prove useful for your business.

Editor: Toshie Furubayashi



Contents

  1. Implementing JMAG
  2. Product Report
  3. Explaining FEA: Effectiveness of FEA in the Development Process
  4. Fully Mastering JMAG - From the FAQ Files -
  5. Fully Mastering JMAG - Issue 7 Understanding Conditions from A to Z -
  6. Event Information


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