Re: [femm] Linear induction motors

[dcm3c@xxxxxxx]

In a message dated 7/30/00 1:14:54 PM Eastern Daylight Time, 
g.bellussi@xxxxxxxxxx writes:

> My name is Gabriele and I'm a student in electrical engineering at the 
> Politecnico of Turin. Well, I've used FEMM to study electromagnets and I've 
> had the same problem. I solved it by adding a point at the end of the 
> magnetic caracteristic with a slope equal to the air permeability. Perhaps 
> when you attempt to solve your problem, you find a magnetomotive force that 
> is greater than the greatest value in your magnetic characteristic, so FEMM 
> calculates the induction value by appling the slope of the last two points 
of 
> your table.

Yes, Gabriele has it right--the program interpolates linearly off the end of 
the defined B-H curve. If you really want to work in "deep" saturation, you 
have to define the B-H curve out until things really get to unit relative 
permeability. However, the best bet in terms of making sure that the program 
does what you intend is to define points so that the B-H curve is always 
interpolated between datapoints, rather than extrapolated.

Dave.