Hello,First, you've set the length units to millimeters when, from the description of your geometry, things need to be in units of centimeters. Second, I think that you meant to draw your blocks as 2 cm by 0.5 cm blocks so that you'd get a total of 252 Amp*Turns with a current density defined as 2.52 A/mm^2. However, the coil cross-section is actually drawn as 2 cm * 0.4 cm, giving you less total amp*turns than you thought. Lastly, the mesh that you are using around the block is a little bit too coarse for really accurate force computations. You need to refine the mesh around the block a bit, e.g. by imposing a finer mesh density on the lines that make up the pole and block surfaces.
My name is BHASKAR. I am trying to realise the
following in femm but facing problem. I wanted to
realise a variable inductance motor which is actually
a pretty good model for a stepper motor. When the iron
piece is moved away from the gap, the cross sectional
area of the core will decrease, there by decreasing
the inductance.For a constant flux the internal energy
will increase and a force will be exerted on the iron
piece to attempt to restore it to its equilibrium
position. The force F is given by
F = m0 w N2 I2 / 2 lg
Where m0 is the permeability of free space , w is the
width of the air gap, N is the number of turns and I
is the current and lg is the length of the air gap.
For a force of 0.2 N, current of 1 amp, air gap of 2
mm and width of 10mm we get the number of turns as
252. I tried to realise this in femm but Iam getting a
force very less than this in the x-direction where did
I went wrong can any one give suggestions.I am sending
the fem file attachment.Please send me your
suggestions.
BBHASKAR
Attachment:
zip00033.zip
Description: Zip compressed data