you se-ho wrote: > To Dear All: > > How are you? > > Simulation (1) I define in the circuit define menu: > circuit 1: +1A > Circuit 2: +1A > circuit 3: -2A (so, acts return ground.) > > Simulation (2) Circuit A: +1A > Circuit B :-1A (this is the return ground.) > then I assigned the "circuit A" to two traces. And I found the > FEMM automatically divided the current half and half. > > I check inductance and resistive loss. I expected them same, but now > > Is there anybody knows the reason? I tried an example like this, except ihn your Simulation (2), I defined: Circuit A: +2 A Circuit B: -2 A so that the total current wold be the same in both cases. I then got exactly the same losses from both cases. Check out the attached examples. Anyhow, the only other thing that I could think of is that femm doesn't necessarily split the current half-and-half between the two conductors if the two conductors are driven in parallel as in your Simulation (2)--it would only split the current exactly evenly if this were dictated by symmetry considerations. It would also be possible to create small imbalances, even in a configuration that is nominally symmetric, if the mesh density is very coarse in the conductors. If the mesh density is very coarse, there is some error in fitting curved boundaries with straight-sided triangles, resulting in a small difference in the area between conductors. One conductor would then be slightly less resistive than the other, pulling slightly more current. Also, if you are evaluating a problem at a high frequency and you don't use enough elements to model the field in the skin depth region adequately, you can get the same sort of effect--slightly different amounts of current get carried in each conductor that you are driving in series, even if the model is nominally symmetric. Dave.
Attachment:
zip00020.zip
Description: Zip compressed data
begin:vcard n:Meeker;David tel;fax:781-890-3489 tel;work:781-684-4070 x-mozilla-html:TRUE url:http://members.aol.com/_ht_a/dcm3c org:Foster-Miller, Inc.;Electrical and Electronic Systems Group version:2.1 email;internet:dmeeker@xxxxxxxxxxxxxxxxx title:Senior Engineer adr;quoted-printable:;;350 Second Avenue=0D=0A;Waltham;MA;02451-1196;USA fn:David Meeker, Ph.D. end:vcard