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I made study of transient to evaluate inrush
current in a single phase transformer using Femm.
First i made a magnetic model of transformer and i
used Femm to evaluate the incremental inductance of the primary winding
Li= dFlux / dI
I used a Lua script to obtain Li as function
of primary current I starting from low current and go on until very hight
saturation of core. The L(i) was evaluted in 25 points and i used linear interpolation between evaluated points.
Then i write the differential equation v(t) =
L(i)*di/dt +R*i(t) and solved this equation using Octave ( www.octave.org ) .
The result was validated with measure on a real
transformer and the error was very small.
I made also a non-linear model of this transformer
for Spice so i can evaluate the inrush current and the armonics in no load
current using transformer in more complex circuits.
I write a paper about this work and it will be
published the next month on italian magazine "Elettrificazione"
If you are italian as me i can post you the
article, i'm not able to translate it in decent english ...
Best regards
Fabio
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