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Re: Potato Chips (fwd)
---------- Forwarded message ----------
Date: Mon, 27 Apr 1998 16:32:31 -0500
From: Michael Smith <md.smith-at-earthling-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Potato Chips (fwd)
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Potato Chips (fwd)
> Date: Monday, April 27, 1998 3:19 PM
>
>
>
> ---------- Forwarded message ----------
> Date: Mon, 27 Apr 1998 15:59:20 GMT
> From: Jim Fosse <jim.fosse-at-bjt-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Potato Chips (fwd)
>
>
> >From: Bert Pool [SMTP:bertpool-at-ticnet-dot-com]
> >Sent: Monday, April 27, 1998 6:28 AM
> >To: Tesla List
> >Subject: Re: Potato Chips (fwd)
> >
> [snip]
> >> The laminations on one of my unpotted neons is out of square. The
thing
> >> is twisted looking and I don't like the way it looks so I took it
all
> >> apart. The laminations were stuck together with something like
varnish or
> >> polyurethane. I decided to sand blast the laminations to remove the
> >> varnish.
> >
> >[snip]
>
> >Gary - do *not* remove the varnish off the laminations! The varnish
is there to
> >electrically isolate each metal plate from the next. As I recall, the
insulation
> >reduces either hysteresis losses or eddy current losses in the
transformer.
>
> Bert,
> I used to think that also but, I've 2 1kW arc lamp ballasts
> that are shunt regulated auto transformers that have the laminations
> arc welded together. Several of my microwave transformers are also arc
> welded together. I now think that the varnish, besides insulating the
> windings and holding them together, keeps the laminations from
> vibrating and generating acoustic noise.
>
> jim
Everyone is sneaking up on the whole truth of the matter here. This is
kind of fun to watch. the laminations are definately to reduce eddie
current losses in the core. Father Tom was correct in saying that the
insulation is the bluish black stuff. Now, for the weld down the side,
they are to reduce hum from loose laminations. the varnish does that as
well. When they want a phyically robust and quiet transformer in a high
power setting they weld them. Note that when they are not welded they are
bolted. But they are never bolted in microwaves.
As for the placement of the weld, I can only surmise that it is welded in
a spot that is going to have the minimal effect, because there will be
eddie currents there. I would like to know how they decide where to weld
it. I might get in touch with an engineer from Signal or someplace and
get the scoop.
Btw, I learned my bead blasting thin metal lesson on a 1/32" thick
aluminum door on a range exhaust fan. I ended up making the new one out
of brass shim stock. :)
Michael Smith
md.smith-at-earthling-dot-net