Re: NEC-LIST: Coil Q

At 07:56 AM 2/8/2005, drcuthbert_at_micron.com wrote:
>I am now convinced that my inductor Q calculations have been way off. I
>am investigating this and have been drawing diagrams of the magnetic
>field at each wire to get an idea about proximity effect and how it will
>crowd the current into a small area of a conductor. When I get some more
>information I will post it here. Does anyone here have a good way to
>calculate coil Q?

The famous NBS Circular 74 has equations derived from Grove which take into
account proximity effect, etc. The original works by Grove would be a good
start.

As far as analytical techniques go, it's a real ordeal. If you need better
accuracy than the equations from Grove, one can use one of the FEM modeling
programs. Folks designing high efficiency switching power supplies (which
live or die on the magnetics) and electric motors use these to eke out the
last tenth of a percent.

There are some links on a page of mine with the Wheeler equations...
http://home.earthlink.net/~jimlux/hv/wheeler.htm

In particular Marc Thompson has a huge number of papers referenced on his
site (which I have a link to) that might provide some guidance.

> Dave Cuthbert
>
>-----Original Message-----
>From: nec-list-bounces+drcuthbert=micron.com_at_robomod.net
>[mailto:nec-list-bounces+drcuthbert=micron.com_at_robomod.net] On Behalf Of
>Greg Durnan
>Sent: Tuesday, February 08, 2005 8:23 AM
>To: nec-list_at_robomod.net
>Subject: NEC-LIST: Coil Q

James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875

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