Re: The contour creation for force calculation

["jim_271" <jim271@xxxxxxxxxxx>]

The small mesh should be used around the solenoid components and the 
air gap, but some distance away you can use a larger mesh size to 
speed up the calculation. You can see an example using two sizes here:
http://web2.airmail.net/jd4usa/guncoil5.htm

(The outer-most boundary that defines 'infinity' is not shown in this 
illustration.)

When the field strength is large, the BH curves supplied with FEMM 
should be extended with more data points so the relative mu 
approaches unity. You can plot the field for your problem to see if 
you're outside the range of the original BH curve data.

-- Jim



--- In femm@xxxx, "matthewc_98" <matthewc_98@xxxx> wrote:
> Hi All,
> 
> I use FEMM to simulate the solenoid and so far, it works pretty 
well. 
> But there is a question I cannot understand and hope you can help 
me 
> to explain it. The question is as following:
> 
> Currently, when I would like to calculate the pull force of the 
> solenoid, I always creat the contour path as close as possible to 
the 
> surface of core steel bar (the contour is away from the steel bar 
> which means the path is within air). But while I read the User's 
> Manual, I found that Dave suggested user to creat the contour at 
> least two elements from any interfaces and boundaries. 
> Could you tell me that what the definition of the element 
(distance ?
> inch ???)? 
> 
> So far, I used the force data of FEMM to campare force data that 
from 
> our force tester in the lab, and found that the error is within 
15%. 
> (Assume the force data of force tester is ideally correct). 
> Is there any way to narrow the error of force simulation of FEMM?
> 
> Anyway, I really appreciate and satisfy FEMM. 
> Thank you so much, Dave.
> 
> Best Regards,
> 
> Matthew