Re: Dissolve Xfmr laminations

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Daniel Hess by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dhess1-at-us.ibm-dot-com>


All;

Several years ago, list member R. E . Burnett (Newcastle, U. K.) posted a
website which contained photos of a custom built variable-inductor for the
purposes of pig-limiting. Unfortunately, the website is no longer up**.
The thing was basically a large 'E' core in which they'd installed a
single-winding core, then topped with an 'I' core which when clamped
together, formed a complete laminated core. Between the 'E' and 'I' pieces
was a thin sheet of styrene creating an air-gap. By varying the thickness
of the sheet styrene one could vary the amount current supplied to the pig.

This design has always impressed me with it's simplicity and elegance and
since I was recently 'asked' to accept two very large (identical)
transformers it seems that fate is pointing me in this direction. ( Isn't
it wonderful when the knowledge of your hobby becomes so widespread that
people start bringing you 'stuff'?)

I'm not interested in the original windings; these things have a zillion
secondary windings. I want to remove/discard these windings, disassemble
the laminations then reassemble them as a big 'E' core and a 'I' core so I
can (hopefully) do as R. E. Burnett did. Right now the E & I pieces are
stacked alternately which forms the standard closed E core. I expect to use
some sort of varnish when I do the reassembly (Formvar?) but my original
question is how to get the thing apart without destroying it hence the
dissolve question.

I notice that on two opposite corners they've run a bead (arc welded) the
laminations together. I see this frequently on power transformers,
presumably to keep the laminations from buzzing. But doesn't this negate
the effect insulating the individual layers with varnish so as to reduce
eddy currents, since the bead essentially connects them all together
mechanically as well as electrically? At any rate, the bead is small and
will not be difficult to grind off.

Thanks for all the help thus far,

Daniel

** It just moved - T.
http://www.richieburnett.co.uk/tesla.shtml




"Tesla list" <tesla-at-pupman-dot-com> on 01/18/2002 07:39:16 PM

To:    tesla-at-pupman-dot-com
cc:
Subject:    Re: Dissolve Xfmr laminations



Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<evp-at-pacbell-dot-net>

Tesla list wrote:
>
> Original poster: "Loudner, Godfrey by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>
>
> Hi Daniel
>
> I would be concerned about stripping the coating on the laminations that
> protects them from eddy currents. I have never had any trouble getting
apart
> the laminations with a butter knife once a few of them have been removed.
Of
> course it might be very difficult to get out the first few laminations,
and
> the extraction might even destroy them.
>
> Godfrey Loudner

 The oxide coating on the surface of each lamination provides the
necessary insulation, and if the laminations are packed in as tightly as
they should be the varnish won't penetrate the stack.  All along I have
assumed the purpose of this discussion was just to get the laminations,
and not try to use the existing windings.

Ed