[SI-LIST] Re: Why does lamination fail to prevent eddy currents at high frequencies?
- From: Vinu Arumugham <vinu@xxxxxxxxx>
- To: Raymond.Anderson@xxxxxxx
- Date: Thu, 28 Mar 2002 12:55:27 -0800
The eddy current loop can be visualized as starting on the first lamina, passing
through all the laminae to the last one and back to the first one. Insulation
between laminae limits the magnitude of the eddy current at low frequencies.
However, the insulator also acts as the dielectric forming an array of parallel
plate capacitors connected in series along the eddy current loop path. At high
frequencies, this path can have a low impedance resulting in large eddy
currents.
A laminated core can also be visualized as a stack of PCB planes for this
purpose.
At high frequencies, the impedance between the two end planes begins to fall.
Thanks,
Vinu
Ray Anderson wrote:
> Lee Ritchey wrote:
> >
> >
> >You bet! The capacitor formed by parallel plate capacitance is the best in
> >you
> >PCB.
> >
> >Lee
> >
>
> Wasn't the original poster asking about about laminated conductors
> (like a laminated transformer or solenoid core) as opposed to
> a laminated pcb stackup ?
>
> I must admit that I was confused by the wording of his request,
> but got the impression that he wasn't talking about pcb laminations.
>
> If indeed he was talking about laminated cores, then even if the individual
> laminations were insulated from each other by some sort of varnish
> I don't think the capacitance between the laminations would effect
> the eddy currents (or lack of them).
>
> Then again, perhaps I am just confused about the original question :)
>
> -Ray
>
> > Steve Rogers (the original poster) wrote:
> >
> > > I have seen a number of simple derivations explaining why it is a good
> > > idea
> > > to laminate a conductor which lies in a magnetic field. The idea being to
> > > slice up the material in the direction of the flux and hence break the
> > > path
> > > of eddy currents. This is all very well and good, I then find it mentioned
> > > in passing that this technique fails at high frequency but have not yet
> > > found a good explanation as to why?
> > >
> > > Would anyone care to have a stab at an explanation, or maybe poiint me in
> > > the direction of one?
> > >
> > > Thanks in advance
> > >
> > > Steve
>
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