Siddarth, it may be mathematically possible, but I cannot think of a pathological case where it is possible. If we back up to the meaning of induction: the flux density that results from a given MMF, then I don't see where it would ever be possible to attain a higher flux density between two conductors than surrounding either one. I will happily be educated if someone can show a case exotic or not where the mathematical possibility proves true. Regards, Steve. At 04:46 PM 10/28/2005 -0400, Singh, Siddharth wrote: >Ray, >Mathematically speaking if L1(or L2) is less than L2(orL1)by more than a >factor of k square i.e. if L1 <(k^2*L2) then clearly L12 will be larger >than L1. >So for a conductor with small self inductance, lying in vicinity of an >inductive path can make their mutual go above self inductance. > >Siddharth. > > >-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >On Behalf Of Ray Anderson >Sent: Friday, October 28, 2005 3:21 PM >To: si-list@xxxxxxxxxxxxx >Cc: Ray Anderson >Subject: [SI-LIST] Can L12 ever exceed L1 or L2 ?? > >A question for the E&M gurus on the list: >=20 > >Are there any conditions (pathological or not) that the mutual >inductance between two conductors can be greater than the self >inductance of either one? > >=20 > >Since L12 =3D k * sqrt(L1*L2) and the coupling factor k must be -1 < k < = >1 >then this would seem to imply that L12 must be less than or equal to >geometric mean of the self inductances. However this leaves open the >possibility the Lm could be > than one or the other which flies in the >face of the commonly made assertion that Lm must be less than either. It >seems that there must be other qualifying statements to made regarding >the relationship to the self and mutual inductances. > >=20 > >Going back to some of the basic fundamental relationships (such as >Grover's formulas) I can convince myself that for circular conductors >L12 must be less than or equal to either L1 or L2, but how about the >mutual coupling between some other structures say a signal trace and >large planar structure that isn't intended to be be a signal return >path but very well may be ? > >=20 > >I've got a field solver reporting Lm being 2 to 3 times Lself on one >particular problem. I'm trying to determine if the solver is having a >difficult time dealing with the particular geometries involved or if it >is indeed possible despite the common wisdom to the contrary. > >=20 > >Any comments one way or the other are appreciated. > >=20 > >Regards, > >=20 > >-Ray > >=20 > >=20 > >Raymond Anderson > >Senior Signal Integrity Staff Engineer > >Product Technology Department > >Advanced Package R&D > >Xilinx Inc. > >=20 > >=20 > > >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >http://www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: =20 > http://www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > =20 >------------------------------------------------------------------ >To unsubscribe from si-list: >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >or to administer your membership from a web page, go to: >http://www.freelists.org/webpage/si-list > >For help: >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >List technical documents are available at: > http://www.si-list.org > >List archives are viewable at: > http://www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu