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Re: [femm] Inductance - more confusion

Hello Jim,

Actually, both responses are correct. The quantity:
integral(A*Jdv) is non-zero only in the copper area since the term J appears as a multiplier. Outside the copper, J=0 so the interal over the volume outside the copper will be zero.

I do it both ways. Sometimes I'm only interested in Inductance, so I just highlight the copper and then look at AJ. At other times I also want the value of the Coenergy (last item on the picklist). Coenergy requires the entire problem area be highlighted. For this, I highlight the whole area (all the regions including the semicircular outer air boundary) and read both Coenergy and AJ. Try reading AJ both ways and you'll find the values are the same, whether the whole area is highlighted or just the copper.

Regards,
JIm
===================================================

From: jim.bloor@xxxxxxxxxxxxxxxxxxxx
Reply-To: femm@xxxxxxxxxxxxxxx
To: femm@xxxxxxxxxxxxxxx
Subject: [femm] Inductance - more confusion
Date: Fri, 07 Sep 2001 07:52:15 -0000

Hi

Thanks to everone who responded to my plea for info on calculating
inductance. However, I've now received some conflicting
information. I understand that to determine inductance requires
selecting an area of the model and obtaining the energy by
integrating but one source says "integrate over the whole model"
which I take to mean everything right out to the boundary, whilst the
other source says "integrate only over the copper winding area".
Which is correct?

My feeling is that integrating over the whole model is the right way
because the energy originates only from the coil. The magnetic flux
generated would interact with the whole of the model and thus affect
the inductance.

Has anyone found a good source of magnetic data for stainless steels
(other than MatLab)?

Regards
Jim Bloor




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