[SI-LIST] Re: Inductance of wire section
- From: "Mark Potter" <mpotter@xxxxxxxxxxx>
- To: <bill.panos@xxxxxxxxxxxxxxx>, <si@xxxxxxxxxxxx>
- Date: Fri, 5 Sep 2003 13:16:43 -0700
Kim,
The ARRL Handbook for Radio Amateurs is a great reference for this also, =
including information for winding your own transformers
Mark Potter
Lead Applications Engineer
PCB Systems Division
Cadence Design Systems, Inc.
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-----Original Message-----
From: bpanos [mailto:bill.panos@xxxxxxxxxxxxxxx]=20
Sent: Friday, September 05, 2003 1:05 PM
To: si@xxxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Inductance of wire section
Kim-
Frederick Terman gives some brief background and assumptions about the =
formula everyone has been mentioning, in his book: Electronic and Radio =
Engineering (written back in the 40's it is still applicable today) =
-Bill
Kim Flint wrote:
> Hi-
> I'm curious about assumptions made in some of these inductance=20
> formulas. I understand inductance as requiring a coil of wire, wherein =
> magnetic flux would intersect the area of the coil. "Inductance of a=20
> wire segment" doesn't really mean anything without understanding where =
> the rest of the current path forming our coil is located. So I'm=20
> guessing these formulas are approximations based on some set of=20
> assumed conditions, like height above ground or something like that?=20
> Does anybody know what those assumptions are in this case? I'd like to =
> understand where I can expect this formula to be reasonably valid.
>
> thanks!
> kim
>
> At 08:57 AM 9/5/2003, Stuart Brorson wrote:
> >Hi Guys --
> >
> >Thanks for all your answers. I used the following formula from Bart:
> >
> >L =3D K * length * [ ln(4*length/Diam) - 0.75 ]
> >
> >L =3D Inductance in nanohenries
> >D =3D Diameter of wire in cm
> >length =3D Length of wire in cm
> >K =3D 2
> >
> >stuck it into Gnumeric (Linux-based Excel replacement), and got the=20
> >following answers:
> >
> > Unit qnty qnty qnty
> >K 2 2 2
> >Length cm 1 1 1
> >Diam cm 0.08 0.06 0.04
> >
> >Inductance nH 6.324 6.899 7.710
> >
> >depending upon the wire diameter. Using the below figure of 20nH/in, =
> >and knowing that 1in =3D 2.54cm, I get L =3D 7.87 nH.
> >
> >Therefore, I think we have nailed it: L =3D 7nH/cm +/- 10% or so.
> >
> >Thanks again for all the answers!
> >
> >Stuart
> >
> > >
> > > Hi Stuart: The ROT I use is 20nH/in.
> > > BTW, I verifed this using a 2D extractor
> > > and increasing the boundary distance far
> > > away from the wire to minimize mutual indutance.
> > >
> > >
> > > Hope this helps
> > >
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