Re: [femm] single wire -magnetic potential A problem

[rm1176@xxxxxxxxxxx]

Hello, 
My name is Robert Marshall from Messiah College in Pa. My senior project
is design a passive magnetic bearing system. We are wondering if there is any
way to simulate a coil of wire in FEMM. We are also looking for a decent
magnet supplier and any possible leads on finding information on this topic. 

On Wed, 17 Oct 2001 dcm3c@xxxxxxx wrote:

> In a message dated 10/16/01 10:09:23 PM Eastern Daylight Time, 
> tborzic@xxxxxxxxx writes:
> 
> 
> > Hello everybody, My name is Tomislav and as You may assume
> > I'm new here and I am looking for some help regarding FEMM.
> > I am trying to solve some "simple" problem.It goes like this:
> > 1. Round wire,copper, infinite lenghth,we look at cross section
> > ,r=0.075m =7.5cm, I= 100 + j0 A,f= 50Hz, relative
> > permeability is 1.Working with old "pen and paper" i got some results
> > which are sure correct.Point is to get same thing in FEMM.
> > What I do is called "numerical callculations of eddy current in round
> > conductor".I nedd to obtain values of "A" in points r1=0, r2=0.25,
> > r3=0.5 and r4= 0.75. (In point r4 A = 0, boundary conditon,allready 
> > given).
> > So what I need is that some one helps me to solve this,tell me
> > how to define parameters for my problem in FEMM,keeping in mind that I
> > am new here,but in near future i intend to use FEMM rather often.
> > My results are:
> > A1=0.9999951 x10-5 -j0.2109364 x10-7
> > A2=0.8888852 x10-5 -j0.1666658 x10-7
> > A3=0.5555543 x10-5 -j0.6510389 x10-8
> > A4=0.5169879 x10-22 -j0.6638621 x10-19 ( this should be 0 but
> > this is good enough)
> > So I need to obtain this rezults with FEMM.
> > Thanks
> > 
> This problem is really similar to the example at <A HREF="http://femm.berlios.de/tube/tube.htm";>
> http://femm.berlios.de/tube/tube.htm</A> Following a similar chain of reasoning 
> to this example, one can show that the solution for tangentially-directed H 
> as a function of radius r is:
> 
> H = i/(2 Pi R) BesselI[1,a*r]/BesselI[1,a*R]
> 
> where a=(1+j)/d, and skin depth d is d = Sqrt[1/(Pi*freq*mu_o*sigma)] where 
> freq is the frequency in Hz, mu_o is permeability of free space, and sigma is 
> electrical conductivity. R is the outer radius of the wire, and i is the 
> total current carried by the wire. In my notation, j = Sqrt[-1] and 
> BesselI[1,x] is the modified Bessel function of order 1 of the first kind.
> 
> I've attached a .fem solution for the same problem. The agreement with the 
> analytical solution is pretty good.
> 
> > P.S. To mr. David Meeker:
> > i am translating User's manual to Crotian,for my personal needs,and
> > for other students on University of Split, who may need it.When I am 
> > done (about 20 days i guess), I can convert it to *.pdf and send it to you
> > if you want,and make it available for everybody on internet?
> > 
> > Tomislav Borzic
> > tborzic@xxxxxxxxx
> > 
> 
> Great! When you finish it, I'll post it on the web site.
> 
> Dave
> --
> David Meeker
> <A HREF="http://members.aol.com/_ht_a/dcm3c";>http://members.aol.com/_ht_a/dcm3c</A>
>