[femm] Re: Current Density X-Y plot problems

[Dcm3c@xxxxxxx]

In a message dated 1/12/00 12:50:22 PM Eastern Standard Time, 
mperry@xxxxxxxxxx writes:

> Dave,
> 
> Thanks for your response.
> 
> Even if I can't get the absolute value of the distribution can I get a
> relative feel?
> I guess what I would like to know is that will FEMM give me the proper
> distribution shape with just the scale being off. If I export the data
> from FEMM plot for J and integrate this across the length (density
> constant in Y axis) can I back out the total current in the section? If
> so I could then adjust the input J to get to where I need to be.
>
> Am I on the Right track or out in left field?

Well, it's not that the scale is `wrong' per se, it's just the formulation 
that's used. This way of doing harmonic problems comes out of Hoole's 
``Computer-aided analysis of electromagnetic devices,'' in which excitation 
in harmonic problems is defined as source currents. The total current is 
then the sum of the source and reaction currents.

At any rate, you can always do a block integral over the coil to get the 
total current in the coil, because induced currents are included in this 
integral. Since all harmonic problems addressed by the program are linear, 
you can simply scale any field quantity to the total current level you want.

> Do you have a feel for when you will be releasing the next version?
> 
> Thanks again.
> 
> Marty

Things are going somewhat slow, so it's hard to say exactly when a new 
version will come out. I haven't had too much time lately, and there are a 
lot of changes that I want to make before the next ``real'' release to add 
functionality and to fix some aspects of the program that irritate me. In my 
development version, I have already added the ability to add constraints on 
currents in eddy current problems, so that all regions aren't effectively 
``shorted together at infinity,'' and I've also added the ability to join 
different entities together into groups, so, for example, one could turn the 
orientation of a rotor with a single command rather than laboriously moving 
each line, arc, block label, etc. I have yet to add the 
periodic/antiperiodic boundary conditions that have been previously 
discussed. I want to include this before I put out the next release, as well 
as make several other, more minor, changes.

Dave.