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Convergence problem with pure iron?
Hello Everyone, Hello Dave!
well, since I'm new to the group let me introduce myself. My name is
Uwe, I'm living in Frankfurt, Germany.
First of all I wish to express my gratitude to Dave for supplying us
with such a good piece of free software. Thanks.
I'm using FEMM now for some months, first of all to get into the
field of electro-magnetics. I'm a mechanical engineer primarily
dealing with electro-mechanical issues who wants to expand his
understanding. Currently I'm working on a solenoid actuator for a
pressure valve. The model consists of a plunger and some stationary
parts (let's call these bobbin) carrying the coil. Plunger and bobbin
are made of VACOFER S1, that is a high purity iron (more info on this
web-site http://www.vacuumschmelze.de/100p_fra.htm). The coil is
modelled by a rectangle to which a current density is applied
amounting to a current per turn of 0.5A, 1A, 1.5A and so on. For my
inital trials with the FE model I just used M19 steel. These
calcualtions always ran straight. But of course the forces I got were
way off of what to expect. Then I got the data of VACOFER in Excel
and I created my own material entry. But soon I realized that the
computing time rises drastically with the number of data points
used. Sometimes the calculation even seemed to be stuck in an
endless loop. All right I thought, there's to be some trick in making
a suitable non-linear BH curve for the computation and started using
the "pure iron" material entry of the FEMM material database. Now my
model seemed to run reasonable well at least for a current density of
0.8A/m2 (that is 0.5A per turn). But as soon as I switch to higher
currents the calculation seems to stall during the Conjugate Gradient
Solver (the cpu load stays 100% for the fkern process, but memory
usage does not change anymore, the .ans file is not yet created). I
also tried different meshes etc. But at some point the calculation
seems to get stuck. Now, am I rather impatient (my PC is PII300Mhz,
256MB RAM) or do I have a bad model, or is it possible that the
solver gets numerically ill-conditioned during the calculation for a
material like pure iron?
Below I have attached the .fem-file for those of you who might be
interested. Any comments and help will be appreciated.
Thanks
Uwe.
FEMM-File:
[Format] = 3.0
[Frequency] = 0.000000
[Precision] = 1.000000e-008
[LengthUnits] = millimeters
[ProblemType] = axisymmetric
[Coordinates] = cartesian
[Comment] = "Add comments here."
[PointProps] = 0
[BdryProps] = 2
<BeginBdry>
<BdryName> = "Zero"
<BdryType> = 0
<A_0> = 0.000000
<A_1> = 0.000000
<A_2> = 0.000000
<Phi> = 0.000000
<c0> = 0.000000
<c1> = 0.000000
<Mu_ssd> = 0.000000
<Sigma_ssd> = 0.000000
<EndBdry>
<BeginBdry>
<BdryName> = "Mixed"
<BdryType> = 2
<A_0> = 0.000000
<A_1> = 0.000000
<A_2> = 0.000000
<Phi> = 0.000000
<c0> = 8841941.000000
<c1> = 0.000000
<Mu_ssd> = 0.000000
<Sigma_ssd> = 0.000000
<EndBdry>
[BlockProps] = 4
<BeginBlock>
<BlockName> = "Air"
<Mu_x> = 1.000000
<Mu_y> = 1.000000
<H_c> = 0.000000
<H_cAngle> = 0.000000
<J_re> = 0.000000
<J_im> = 0.000000
<Sigma> = 0.000000
<d_lam> = 0.000000
<Phi_h> = 0.000000
<LamType> = 0
<LamFill> = 1.000000
<BHPoints> = 0
<EndBlock>
<BeginBlock>
<BlockName> = "Pure Iron"
<Mu_x> = 14872.000000
<Mu_y> = 14872.000000
<H_c> = 0.000000
<H_cAngle> = 0.000000
<J_re> = 0.000000
<J_im> = 0.000000
<Sigma> = 10.440000
<d_lam> = 0.000000
<Phi_h> = 0.000000
<LamType> = 0
<LamFill> = 1.000000
<BHPoints> = 11
0.000000 0.000000
0.650050 39.788750
1.125100 79.577500
1.415200 159.155000
1.738507 1530.335000
1.868145 6886.512000
2.000000 15915.500000
2.127420 39023.580000
2.229765 80342.630000
2.332111 143086.500000
2.560000 318310.000000
<EndBlock>
<BeginBlock>
<BlockName> = "Coil"
<Mu_x> = 1.000000
<Mu_y> = 1.000000
<H_c> = 0.000000
<H_cAngle> = 0.000000
<J_re> = 1.767068
<J_im> = 0.000000
<Sigma> = 0.000000
<d_lam> = 0.000000
<Phi_h> = 0.000000
<LamType> = 0
<LamFill> = 1.000000
<BHPoints> = 0
<EndBlock>
<BeginBlock>
<BlockName> = "M-19 Steel"
<Mu_x> = 4416.000000
<Mu_y> = 4416.000000
<H_c> = 0.000000
<H_cAngle> = 0.000000
<J_re> = 0.000000
<J_im> = 0.000000
<Sigma> = 0.000000
<d_lam> = 0.000000
<Phi_h> = 0.000000
<LamType> = 0
<LamFill> = 1.000000
<BHPoints> = 13
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1.740000 7957.750000
1.870000 15915.500000
1.990000 31831.000000
2.045964 55102.040000
2.080000 79577.500000
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