Re: [TCML] transformer theory questions

["David Rieben" <drieben@xxxxxxxxxxx>]

Hi Gary,

Yes, I too have seen many of the microwave oven type transformers
that have a weld seam along the laminations. I suppose it must be as
you suggest - just a single weld seam, for if the laminations were shorted
in two or more locations, that would provide the "return" path for the eddy
currents. That is why each individual lamination is insulated with a thin 
film
of some dielectric material on both sides. I do know that when a "solid" bar
of core material is inserted into a coil activated with AC, the "core" does
quickly begin to heat up. Intentional generation (and shorting of) eddy
currents is the principle by which inductive heating is accomplished.

David Rieben




----- Original Message ----- 
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, September 21, 2009 10:47 AM
Subject: RE: [TCML] transformer theory questions


Hi David,

I had thought about the possibility of eddy current losses, but I also 
recall seeing some cores having a weld tying all of the laminations 
together, clearly shorting the laminations.  It may be that to get eddy 
currents, the laminations may need to be shorted in two different places?  I 
don't recall if the welded cores I've seen had a single bead or not, and 
it's unclear if a hack saw hack job would also short in multiple places. 
But "don't do it" is surely the safest course of action!

Regards, Gary Lau
MA,  USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of David Rieben
> Sent: Monday, September 21, 2009 11:09 AM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] transformer theory questions
>
>
> Hi Thomas, Gary, all,
>
> I would also suspect some unwanted eddy current losses/heating of the core
> to result from
> "cutting across the laminations", too, as this would almost certainly 
> short
> some of the
> laminations together, electrically.
>
>
> >> What happens if you cut into the frame of a transformer, cutting the
> >> across
> >> the iron lamination?
>
>  > I wouldn't do that.  I expect that the consequences are largely
> mechanical - like you won't be able to get it back together again after 
> the
> laminations are mangled.
>
> \
> > Many thanks
> >
> > Thomas
>
> > Regards, Gary Lau
> > MA, USA
>
> David Rieben
>
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