Re: Am I courting disaster?

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

Original poster: Dave Leddon <leddon1-at-llnl.gov> 

At 07:07 AM 1/29/2004, you wrote:
>Original poster: Zagarus Rashkae <arbitrarily_random-at-yahoo-dot-com>
>Hi Dave,
>
>I don't think the streamer would want to strike the
>primary at all. Although there may be some flashover
>concerns if the pig were to get hit directly on the HV
>out terminals because it may flash over internally to
>the 240V outlet ground. If you have a good strike rail
>then you shouldn't have to worry about the pig
>flashing over. A lightning arrestor certainly couldn't
>hurt and wouldn't be that much of an investment
>compared to that beautiful clear pig :)
>
>How and where did you get that much acrylic resin to
>encase the pig? I imagine it would have cost quite a
>bit...
Hi Chris,

About $100 at Tap Plastics, a chain local to California.  Actually, this is 
my second attempt at re-casing this transformer in plastic.  The first time 
I used half-inch Lexan, which normally would be too expensive to use for 
this sort of thing but I got a bunch of it free.  The problem with the 
polycarbonate was that it leaked right from the start.  I'd repair one leak 
and another would appear.  I asked the guys at Tap Plastics about this and 
they said that they never recommend Lexan for this sort of thing because it 
just doesn't glue up well whereas with acrylic and a methylene chloride 
solvent based glue you can get a perfect, water-tight joint.  I decided to 
switch to acrylic when, after fixing the third leak and refilling with oil, 
I got the bright idea of applying just a small amount of air pressure 
through the pressure relief hole in the lid to reveal any additional 
leaks.  You can see where this is headed, can't you.  At about 10 psi I 
heard a loud ka-blooee as one side of the tank exploded out, releasing the 
entire two gallons of oil onto the garage floor.  You have no idea what a 
mess a couple of gallons of transformer oil can create until you've done it 
yourself.

Dave

>Regards,
>
>Chris Lu
>
>--- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: Dave Leddon <dave-at-leddon-dot-com>
> >
> >
> >
> > I recently re-cased a 10 KVA pig in acrylic to
> > reduce the size and weight
> > of the thing.  See picture:
> > http://nick_tesla.home-dot-comcast-dot-net/TheVisiblePig.jpg
> > The finished size  ended up 11 x 11 x 14 inches with
> > the volume of oil
> > dropping from 16 gallons to 2 and the weight from
> > 300 to 170 lbs.  In the
> > process I reduced the external connections to the
> > bare minimum, 240 volts
> > in and 14400 volts out and floated everything with
> > respect to ground.  This
> > means that the coil tank circuit also floats which
> > has a certain
> > appeal.  The performance of the coil is the same as
> > it was when one side
> > the supply voltage was tied to the RF ground
> > although the primary tuning
> > does seem to be a bit sharper.  My only concern
> > about this configuration is
> > what happens to the energy following a strike to the
> > primary? It would
> > appear that the only path to ground would be back
> > through the transformer
> > to utility power.  Do I need to install a lightning
> > arrester between one
> > side of the tank circuit to the RF ground?
> >
> >


***************************************************************************
David H. Leddon
Lawrence Livermore National Lab