[Getdp] High error by calculating the time derivative in postprocessing

[Jürgen Schuhmann]

Dear Christophe,
first i want thank you for developing such a mighty tool like getdp.
I am calculating the current distribution in busbars for currents up to 5kHz 
with getdp.
In case of higher frequencies the skin and proximity strongly inluences the 
current distribution. This leads to very low currents in the interior of the 
busbars. 
By posprocessing the current-distribution a high error occurs at the 
locations, where the vector-potential a is very low. I think this results 
from the time derivative of the vector potential in the formula: 
jz=sigma[]*CompZ[(Dt[{a}]+{ur}).
Of course, the error vanishs by decreasing the time step. But i have to set 
2000 timesteps per period to get an useful result.
If i calculate the same problem in frequency domain, then the resulting 
current distribution is very accurate.
So my Question:
Is there any way to increase the accuracy of the time derivative used in the 
postprocessing?
By the way is there a way to calculate the time derivative of a an integral, 
i.e.
Dt {Integral { [ - sigma[]*CompZ[({a} ]  ] ; In DomainC_Mag ;Jacobian Vol ; 
Integration CurlCurl ; } }}
This would be useful because the time charakteristic of the integrated field 
is much smoother than the local field.

Thank you for your help.

J. Schuhmann


-- 
___________________________________________________
Dipl.-Ing. Jürgen Schuhmann
Simulation u. Hardware-Entwicklung

Enertex Bayern GmbH
Geschäftsführer: Dr.-Ing. Michael Schuster

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