JMAG Newsletter Fall,2011Fully Mastering JMAG

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An Introduction to JMAG Technical Support
- Accounting for the magnetic hysteresis characteristics -

We, support members, are continuously working on early solutions to the problems we received so that you can conduct your tasks much smoother. In this series, I would like to introduce the scenes in which JMAG technical support service supports our customers while communicating our customers and support members.
This time I would like to introduce the case that one of our support member offered a solution for the problem that cannot work around with the standard features.

Mr. A: Has worked on JMAG for three months, putting effort into actuator analysis
Mr. B: Mr. A's boss. He ordered Mr. A to conduct search how close results they can obtain to actual measurements using JMAG.
Support: JMAG technical support contact person

The deadline for Mr. A's JMAG analysis result report is approaching, but a problem has occurred with the analysis result so he is conferring with his boss.

Mr. AThe values of electromagnetic forces are OK, but response characteristics do not match. What should I do? (*1)
Mr. BThe values of electromagnetic force match to each other. So response characteristics should do as well. Do you account for hysteresis? (*2)
Mr. ANo. I do not. I don't know how to account for hysteresis.
I found no descriptions about it on the JMAG manual.
Mr. BContact JMAG support and learn how to do that, and search it!

Mr. A decided to inquire his question to JMAG support via e-mail.

Mr. AI performed actuator analysis, but the response characteristic does not match with the actual measurement.
I think that is because I do not account hysteresis. Please tell me how to account for hysteresis.
SupportI see. It takes calculation time when you perform a calculation that accounts for hysteresis.
Before that, please let me check if you are accounting for eddy currents.
For example, if it is a lump of material then the effect from eddy currents is large, and it has effects on the response characteristics as well. (*3)
Mr. AReally? This time I use just a structural material. OK, I will check the eddy current.

Mr. A performed an analysis accounting for eddy currents.

Mr. AOh! I got almost the same measurement with the actual measurement after accounting for eddy currents!
Mr. BAccounting for eddy currents result in matching them with each other even without accounting for hysteresis.
Um-hum To make it sure, please check how much the influence of remanent magnetization is. (*4)
Mr. AThe contact person of the support said that it takes calculation time for accounting for hysteresis...
I will consult with the support as to the details.

Mr. A contacted the support again.

Mr. AI obtained a result that is close to actual measurement after accounting for eddy current.
Does this mean no remanent magnetization influenced this analysis?
How can I check the degree of remanent magnetization influence?
SupportYou obtained the result close to actual measurement. That's good.
You have three choices of the methods to accounting for the magnetic hysteresis, and I will suggest the most appropriate one.
There are some easy methods (*5) to account for the hysteresis, but they do not account for the remanent magnetization. So you cannot apply them for this time's analysis. Also, concerning the method (*6) that keeps a log of the operating point of the magnetizing properties, some other data is required for some of those methods, so it will take rather long time.
You are in a hurry, so I will suggest the method that easily estimates the degree of the influence of remanent magnetization.
Mr. AA simplified method is enough. I would like to know the degree of the influence, so please tell me the concrete operation procedure.
SupportI see. I will explain that. (Refer to the column for the details.)

- After that, Mr. A indicated that the influence of remanent magnetization is small and Mr. B accepted the conclusion.

In Closing

The above mentioning is just an example, but JMAG support members are proficient in the restrictions on how to use or applicable scopes of JMAG. So, we can suggest some techniques that are not described in the manuals. Even if you think what you desired to do using JMAG is impossible, please contact JMAG support and inquire about it. We will suggest creative analysis methods.

The following is a collection of explanation by JMAG support members.

*1. The things that can be a problem for actuators are the response characteristics for the electromagnetic force and applied voltage in each of the moving parts.
*2. If the values of electromagnetic forces match, it is assumed that transient phenomenon is not correctly reflected. In such case, what to focus on is rather a factor arise from transient such as eddy current influences than whether the magnetic hysteresis characteristics is correctly reflected.
*3. Usually magnetic steel sheets are not used at moving parts of the actuator, and there is high possibility of large eddy current generation.
*4. Actually, magnetizing properties have hysteresis properties, so it is necessary to check the influence to the result.
*5. These are methods that calculate hysteresis loss from the magnetic flux changes, and this is used for the iron loss calculation.
*6. Normal magnetic field analysis uses direct current properties, so creating a user subroutine is necessary to keep a log of the operating points of the magnetizing properties.


[Column]: In order to accounting for remanent magnetization

"Remanent magnetization" refers to a situation in which the magnetization of an object that has gone through external excitation does not return to zero even after the cause of said excitation has disappeared. To express the remanent magnetization it is required not only the information on where the operating point currently is but on the log that records the track of the operating point. In order to handle this phenomena accurately on the current version JMAG, the only method is creating a user subroutine. Creating a subroutine requires related knowledge and it will be a hard and time-consuming task such as programming.
Then, this is a simplified method but I will introduce an accounting method of the remanent magnetization characteristics using the magnetization analysis function. With this method, assuming that the status with remanent magnetization is a permanent magnet, perform the analysis with defining the magnetic material as a magnet in the middle of the analysis. I will divide this analysis into two parts, where Step 1 is analysis with the external excitation status ON, and Step 2 is analysis with the external excitation status OFF. In step 1 we carry out analysis of ordinary initial magnetizing properties, and in step 2 we apply remnant magnetization to the object based on the magnetization field distribution of the final results of step 1. Using JMAG's magnetization analysis function enables you to decide the magnetization from the magnetization field distribution result.
Please be note that what you can account for is only the remanent magnetization when exciting once, and cannot do the remanent magnetization when repeating exciting status.


Contents

  1. Implementing JMAG
  2. Model-based Development
  3. FEA Description
  4. Fully Mastering JMAG - Part 3 Evaluating Results and Viewing Models from A to Z -
  5. Fully Mastering JMAG - An Introduction to JMAG Technical Support -
  6. Event Information


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