Transcript MCWF_TimeConstant.ppt

Modular coil winding form EM analysis
1/3 model, cover 120
degree (totally 18 coil
forms)
Air
z
6 coil forms (1/3 model)
Material: stainless steel (80K)
A1
A2
Modular coil winding form EM analysis
1.Coil form mesh size: 2”.
2.Stainless steel resistivity at 80K: 65e-8 ohm-m.
3.Time step: 0.3ms.
4.Poloidal cuts by modifying elem material property,
to simplify the modeling.
A1
B2
C2
C1
A2
B1
Poloidal cuts
Welding
Material: stainless steel
B1
A1
C1
C2
B2
A
2
Boundary conditions
Symmetry planes (flux parallel)
Bz
z
A1
B1
C2
C1
A2
B2
Bz
At z=+57” and z=-57”, give arbitrary external
magnetic field Bz=-1T@t=1E-6s, then Bz ramp to
0T@t=1E-4s and lasts for 40ms.
Note: symmetry BC is an approximation
because CYCLIC doesn’t work due to the
complexity of this model (i.e. highly
unmatched mesh at the low and high
edges).
TIME
Evaluation point
Estimate time constant
z
1. Choose the center point at z=0 to read B result. Choosing different point will have different result.
Several evaluation points can be chosen to have an average result for time constant.
2. Estimated time constant: 8ms (40ms range), 12ms (~80ms range), 19ms (~190ms range)
3. Eddy current decays faster at the beginning and then more and more slowly after a while. But if the
island size becomes small enough, it is still acceptable. Otherwise, it may be a problem.
1.00E-06
5.05E-05
1.00E-04
2.00E-02
3.98E-02
4.01E-02
4.25E-02
4.49E-02
4.73E-02
4.97E-02
5.21E-02
5.45E-02
5.69E-02
5.93E-02
6.17E-02
6.41E-02
6.65E-02
6.89E-02
7.13E-02
7.37E-02
7.61E-02
7.85E-02
8.09E-02
8.33E-02
8.57E-02
8.81E-02
9.05E-02
9.29E-02
9.53E-02
9.77E-02
0.10008
0.10248
0.10488
0.10727
0.10967
0.11207
0.11447
0.11687
0.11927
0.12167
0.12407
0.12647
0.12887
0.13126
0.13366
0.13606
0.13846
0.14086
0.14326
0.14566
0.14806
0.15046
0.15286
0.15526
0.15765
0.16005
0.16245
0.16485
0.16725
0.16965
0.17205
0.17445
0.17685
0.17925
0.18165
0.18404
0.18644
0.18884
BSUM_84404
0.269136
0.196311
0.106803
1.58E-03
6.74E-04
6.96E-04
6.29E-04
5.65E-04
5.08E-04
4.56E-04
4.08E-04
3.65E-04
3.26E-04
2.92E-04
2.61E-04
2.32E-04
2.07E-04
1.86E-04
1.66E-04
1.49E-04
1.33E-04
1.19E-04
1.07E-04
9.67E-05
8.72E-05
7.85E-05
7.11E-05
6.50E-05
5.88E-05
5.27E-05
4.89E-05
4.47E-05
4.13E-05
3.82E-05
3.47E-05
3.25E-05
2.99E-05
2.78E-05
2.58E-05
2.40E-05
2.28E-05
2.10E-05
2.01E-05
1.87E-05
1.76E-05
1.69E-05
1.55E-05
1.45E-05
1.41E-05
1.34E-05
1.26E-05
1.14E-05
1.09E-05
1.00E-05
9.46E-06
9.40E-06
8.70E-06
8.49E-06
7.59E-06
7.18E-06
6.73E-06
6.40E-06
5.96E-06
5.52E-06
5.50E-06
5.13E-06
4.71E-06
4.70E-06
time constant (ms)
4.73871734
7.972166998
10.282
11.88059914
13.70875
16.18444444
18.644
Eddy current pattern (lower half)
y
x
z
B2
A2
B2 cut
Eddy current pattern (upper half)
y
z
x
B2
A2
A2 cut
Eddy current pattern (lower half)
C1 cut
C1
C2
y
x
z
Eddy current pattern (upper half)
C2 cut
C1
C2
y
z
x
Eddy current pattern (lower half)
A1 cut
y
z
B1
x
A1
Eddy current pattern (upper half)
B1 cut
y
z
x