Re: Jacobs ladder ballast (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 15 May 2005 09:04:56 -0700 (PDT)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: David Speck <dave@xxxxxxxxxxxxxxxx>, hvlist@xxxxxxxxxx
Subject: Re: Jacobs ladder ballast

Hey, David!

I'd love to try it, but I'm not sure where I'm going
to get that many MOTs for cheap.  Even on eBay, people
tend to want $20 or more for one.  I could easily
spend many $100's on a bank of 15...unless somebody on
this list knows of a really cheap source! :)

I'd love to see some pictures/movies of that GE
display.  Wowzers.  I suppose most of you all have
seen these pictures/videos before, but I found them
quite worth watching: 
http://205.243.100.155/frames/longarc.htm

The one from the 500kV disconnector malfunction is
particularly impressive.  It really goes to show that
it's not just voltage that influences arc length, it's
current too.

73,
Aaron, N7OE

--- David Speck <dave@xxxxxxxxxxxxxxxx> wrote:
> Aaron,
> Only problem with using heater elements is that they
> are dissipative 
> ballasts -- they convert a good portion of your
> power to useless heat.
> 
> Using inductive ballasts converts significantly less
> of the input power 
> to heat, allowing more power for the display.
> 
> I'd suggest using a bank of 9 to 15 microwave oven
> transformers with 
> their outputs shorted.  If you run multiple parallel
> chains of three 
> transformers, then none will ever see more than
> 220/3 volts, and they 
> will run reasonable cool.  Use you relays to  switch
> in more or fewer 
> chains to get more current to your pig.  These would
> not have to be  in oil.
> 
> Are you familiar with the huge continuous arc
> display that was shown at 
> the 1939 NY World's fair by GE?  They used three
> seriesed three phase  
> HV transformers to get a three point 1.5 megavolt
> continuous flaming 
> discharge.  The transformers were specially designed
> for the system, and 
> used high leakage inductance to limit the arc
> current, just like a neon 
> sign transformer. 
> 
> I have a neat book by T. Blalock describing the
> production of HV 
> transformers by GE at Pittsfield MA, and I've
> corresponded with him 
> about the display.  His mentor at GE designed the
> NYWF display  system, 
> can't remember his name  at the moment, but he's
> gone now.  I'd love to 
> see a movie of the whole show.  I understand that
> parts of the show were 
> used in the intro to a "GE Theater" series in TV in
> the 50's, and sort 
> of dimly remember seeing it, but I'd sure like to
> see the whole thing 
> some day.  Man, wouldn't that be a display do see
> again!  Unfortunately, 
> the transformers were parted out, and only one of
> them remains intact, 
> but unused now.
> 
> Dave Speck
>