George, I agree that any model that shows inductance going to infinity for a an=20 infinitly large plane is wrong. Finite flux can result in infinite ( or very large ) inductance, since=20 inductance is the flux density / mmf. I suspect that what is happening in the model is that the finite mmf is=20 getting improperly approximated as either a very small number or zero. Regards, Steve. At 11:59 AM 8/6/2004 -0700, George Tang wrote: >I disagree with what you are suggesting. If you have a wire above a plane >with a finite current flowing through the loop, even with infinite plane >size and thickness, the DC inductance cannot be infinite. You can= integrate >the flux density out to infinity, but the total flux should add up to the >loop current (enclosed current), which is finite, so the total flux is >finite. This will result in a finite inductance (internal and external). > > >George > > > >-----Original Message----- >From: si-list-bounce@xxxxxxxxxxxxx >[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ege Engin >Sent: Friday, August 06, 2004 6:16 AM >To: steve weir >Cc: scott@xxxxxxxxxxxxx; cclewell@xxxxxxxxx; si-list@xxxxxxxxxxxxx >Subject: [SI-LIST] Re: Internal Inductance > > >Steve, the paper cited by Jayaprakesh also demonstrates that there is a >non-zero internal inductance, which decreases with frequency, associated >with an infinite ground plane. Actually the given equation also suggests >that the internal inductance tends to infinity at dc. However, the >ground plane is assumed to be also infinitely thick, which makes the >obtained expression less and less reliable at low frequencies. I think >for an infinitely wide plane having a finite thickness your statement >might be true though. It might be that the divergent behavior I observed >is due to the fact that the total loop inductance tends to infinity at >dc (since the current loops get larger and larger), and not the internal >inductance of the plane. > >Ege > >steve weir schrieb: > > > Ege, for infinite planes, I think you mean the inductance tends to > > zero. Since the current distributes over an infinite area, the flux > > density tends towards zero as does any current impeding counter-EMF. > > > > Steve. > > At 11:10 AM 8/6/2004 +0200, Ege Engin wrote: > > > >> Craig, > >> > >> The internal inductance is frequency dependent, and simulations at > >> multiple frequency points are necessary as Scott explained. L.J. > >> Giacoletto; "Frequency- and Time-Domain Analysis of Skin Effects", IEEE > >> Tran. Mag., Jan. 1996, gives some analytical formulas for rectangular > >> conductors. > >> > >> I assume you want to obtain the internal inductance at dc. The method > >> that we apply to extract the dc internal inductance of conductors is to > >> simulate at a very high and a very low frequency (if you have an > >> eddy-current solver such as Ansoft Maxwell 2D). The difference in the > >> inductances gives the dc internal inductance. Though, I think it is > >> difficult to obtain a definite internal inductance value for conductors > >> in the presence of planes. The reason is that if the planes are assumed > >> to be infinite in extent, the current should distribute itself > >> uniformly in the planes at dc. But this should also mean that the > >> inductance goes to infinity! Although I could not find a supporting > >> statement in the literature, it seems obvious, and simulations have= also > >> shown this divergent behavior. As a result, this method gives a= definite > >> internal inductance value only if the planes have a finite (and known) > >> width. > >> > >> Regards, > >> Ege > >> > >> Scott McMorrow schrieb: > >> > >> >Craig, > >> > > >> >I don't believe there is a straightforward analytical formula for > >> >non-round conductors. When you start getting into internal inductance > >> >for trace geometries in the presence of a plane, then it will > >> definitely > >> >depend on the shape and proximity to the other conductors. However, > >> >this problem is easily solved by several different field solvers. > >> > > >> >Commercially, Ansoft Maxwell 2D does a very good job of extracting > >> >inductance at multiple frequency points. You just have to be sure to > >> >use the impedance matrix. > >> > > >> >Academic codes such as FastHenry from MIT and Simian from Dean Neikirk > >> >at the University of Texas can correctly solve for frequency dependent > >> >inductance and resistance of arbitrary shapes. Links to these can be > >> >found at http://www.fastfieldsolvers.com/links.htm > >> > > >> >Or, if you are dealing with stripline traces, you can use a boundary > >> >element method or method of moments field solver to run two problems. > >> > > >> >Problem 1) your rectangular trace at the normal thickness centered > >> >between the planes. > >> > > >> >Problem 2) a very very thin trace centered between the planes. > >> > > >> > > >> > > >> >regards, > >> > > >> >scott > >> > > >> > > >> >Craig Clewell wrote: > >> > > >> > > >> > > >> >>Greetings, > >> >> > >> >>Does anybody out there have an equation handy to calculate the > >> internal > >> >>inductance of a square, rectangle, or any other object that is not > >> >>round? I already know that the internal L of a round wire is > >> (u*length) > >> >>/ (8*pi), but I'm not looking at using a round wire. I've read > >> that it > >> >>should be about 20% of the external inductance, however I want to= dial > >> >>it in better than that. I'm so used to neglecting this, that I know > >> >>find myself at a "loss".....ok...that wasn't funny :>) > >> >> > >> >>Thanks for sharing.... > >> >> > >> >>Craig > >> >> > >> >>------------------------------------------------------------------ > >> >>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: > >> >>//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: > >> >> //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 > >> >> > >> >> > >> >> > >> >> > >> >> > >> >> > >> > > >> > > >> > > >> > >> -- > >> Diese E-Mail kann Betriebs- und Gesch=E4ftsgeheimnisse, dem > >> Anwaltsgeheimnis unterliegende oder sonstige vertrauliche > >> Informationen enthalten. 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Thank you. > >> > >> > >> ------------------------------------------------------------------ > >> 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: > >> //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: > >> //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 > >> > > > > > > > > > >-- >Diese E-Mail kann Betriebs- und Gesch=E4ftsgeheimnisse, dem= Anwaltsgeheimnis >unterliegende oder sonstige vertrauliche Informationen enthalten. Sollten >Sie diese E-Mail irrt=FCmlich erhalten haben, ist Ihnen die Kenntnisnahme= des >Inhalts, eine Vervielf=E4ltigung oder Weitergabe der E-Mail ausdr=FCcklich >untersagt. Bitte benachrichtigen Sie den Absender der E-Mail und vernichten >die empfangene E-Mail. Vielen Dank. > >Since this e-mail contains confidential information, it must be treated= with >utmost confidentiality. Any person who may get in contact with this >information by mistake should not take any notice of the topic and should >not pass on or duplicate any part of this information. The e-mail has to be >destroyed and the sender of the the e-mail has to be informed immediately. >Thank you. > > >------------------------------------------------------------------ >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: >//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: > //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: //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: //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