Magnetic circuit model

[janas21]

Hello,

I have to create a mathematical model for an magnetic circuit application. The model should not be in FEM, since the result of this model has to be checked up through FEM simulations. So for the creation of this model we have to use only mathematical functions. Is there any recommended books or papers in the literature as a start up?

Thanks in advance.

 

[MagMike]

If your magnetic circuit is simple, such as a magnet on a piece of steel or a simple dipole then one could use mathematical equations. Anything more complex than this requres FEM.

Keep in mind, even in the simple case, the mathematical equations are only approximations. A properly constructed finite element model will be more accurate.

Moskowitz's book: Permanent Magnet Design and Application Handbook has a chapter on this, although it is rather complex.

 

[israelkk]

Electromagnetic devices, by Roters 1941.

MagMike

An analytical model is quite accurate for many engineering cases. A good practice and many times cheaper and faster to do analytical analysis and build a model and test it than do FEM analysis. Few months ago I happened to design a 40 lbf tubular solenoid and used both analytical and FEM analysis. The analytical model gave 60 lbf and the FEM gave 80 lb while the actual solenoid gave 40 lbf.

But, its main advantage of analytical analysis is that you can easily simulate transient and dynamic conditions such as a case of a solenoid valve open and close time constants against the fluid pressure, return spring forces, plunger mass, inertia, friction, etc.

Trying to do it in a static FEM program is impossible unless you enslave the FEM program to a numerical/analytic computer program and with every time step of the simulation run the FEM program and uses the force result back in the numerical computer program. Such an analysis can take days or even more on a PC especially if you need an accurate force from the FEM program (very large model with many fine elements).

2D FEM program can not calculate magnetic side forces in an axisymmetric solenoid and the resultant friction between the plunger and valve body as a result of it. While in reality there is a side force due to out of concentricity of the plunger.

 

[drafter007]

Hello,
a good book is Kallenbach: "Der Gleichstrommagnet"

http://books.google.com/books?id=Ya...ts=DBPHditoYg&sig=tGPAl1Q3WVVj3emhtx-ujpHGemE

In it the network method for magnetic circuits is described on page 99f . This book helped me very much.
Best Regards
Markus

 

[MagMike]

israelkk: You raised a number of good points. I was too quick to knock analytical expressions. Thanks for setting me straight.

I read too much into janas21's latest posting. I had the impression that janas21 was looking for exact analytical expressions to verify an FE model.

Yours and drafter007's book recommendations are good ones.

 

[janas21]

Thanks a lot for the help and the book suggestions, there are a good starting point, for my work.