Re: [femm] Bobin (L,R) calculation

[David Meeker <dmeeker@xxxxxxxx>]

jire602000 wrote:
> Hello .
>
> I am new with this femm software and I need some advice .
>
> I want to do a bobbin of 20 turns for metal detection.
>
> The working frequency is 25Khrz.
>
> Building the model is OK  , but how can I extract the value of 
> inductance and resistance of the bobbin  from  the femm calculations ?
>
> Thanks for your help
>
>
>
>
> Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
There's an example at http://femm.berlios.de/induct1/induct1.htm that covers
a few different ways that you can derive inductance.  

Anyhow, since your frequency is sort of high so that there might be significant
skin/proximity losses, and since and the wire count isn't too big, I'd suggest
modeling each turn in the coil individually, like in the example at: http://groups.yahoo.com/group/femm/message/1319
You'd get inductance via any of the methods described in the inductance example,
and you'd get resistance by integrating the losses over your entire domain
and dividing by the square of the RMS current in each turn.  The only trick
w.r.t. the inductance is to remember that in the AC case, if you use the
volume integral of stored energy, the average stored energy is: (1/2) L *
(RMS i)^2 which equals (1/4)*L*(Peak i)^2   People sometimes misplace a two
in there somewhere when doing the AC calculation if they are using peak currents.

Dave.