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# Re: [femm] H in magnets

- To: femm@yahoogroups.com
- Subject: Re: [femm] H in magnets
- From: dcm3c@aol.com
- Date: Fri, 5 Oct 2001 23:25:09 EDT

In a message dated 10/5/01 1:11:04 PM Eastern Daylight Time, jornet@ee.upc.es writes:

> We're trying to simulate three induction motor and we're worry about these topics. First of all
> -How can we perform a simulation with a material with real histeresys cicle. What's the meaning of this angle you called in femm

f_h?
Well, femm uses a simple but dirty model of hysteresis wherein hysteresis is represented as a fixed phase lag between H and B that is independent of frequency. The angle of that phase lag is defined by the parameter f_h. Now, this model only yields elliptical hysteresis loops--real hysteresis loops look a bit more complicated than that. However, if you pick the parameter right, you can get OK results as far as losses and phase shifts.
I

> s it necessary to calculate histeresys losses for an accurate result of eddy current losses?

Well, some machines can have significant hysteresis losses.
-

> If we make a magnetostatic simulation for a particular position of the rotor, if we change this position to observe another position of the rotor, do we have to make any additional hipothesys?

I don't think I understand the question. Are you perhaps asking about hysteresis with respect to magnetostatic problems? For magnetostatic problems, femm neglects hysteresis effects.
-

> What does The boundary depth skin effect mean? How can we use it in a three phase induction motor with double caged rotor?

This boundary condition is probably irrelevant to what you are doing. This is basically a surface impedance boundary condition if your solution domain bordered on some material subject to eddy currents, the frequency is such that the skin depth is small, and you aren't really explicitly interested in the boundary material. Anyhow, there's a little blurb about this in section 3.7.2 of the manual.
Dave.

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