RE: Big x-ray transformers and Jacobs Ladders.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>

Hi Dave, Phil, et al,

My Diesel Genset is conservatively rated at three phase 18KVA. The Genhead
winding are heavy duty! I have a 3 phase Raytheon radar transformer but I
don't know its current rating, which is to drive my 12" Tesla coil. It's
previous life was in a Nikie missile site. It was making -24KV using (6)
8020 Vacuum tubes.

After this thread, thus far, I am still inclined to purchase the big X-ray
that Jack King is holding for me. A three phase x-ray transformer would be
ideal if there is such a transformer.

Thanks All,
Jim Mora



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Sunday, April 22, 2007 8:32 PM
To: tesla@xxxxxxxxxx
Subject: Re: Big x-ray transformers and Jacobs Ladders.

Original poster: David Speck <dave@xxxxxxxxxxxxxxxx>

Jim,

It's my understanding that the arc length of a JL
is primarily dependent upon the current
available, not the voltage. Once the arc is
established, the voltage drop across it is only a
few hundred volts, if that much. Supplying it
with more voltage doesn't do anything to increase
the arc length. Other list members have reported
that X-Ray transformers have made disappointing
JLs, because they can supply relatively little current.

How much current is your current pole transformer
rated for? If you go for a higher rated
transformer, and can supply it with enough
current, then you should be able to get longer
arcs. However, JLs are hungry beasts, and you do
need a lot of current to drive them. Ed Wingate's
JL draws a maximum of nearly 100 amps at 240 VAC.
I'm not completely certain, but I think he was
driving it with at least a 10 or 15 KVA
transformer to get about 24 - 36" arcs at the final break.

I'll have to dig through my reference books about
the GE flaming 20 foot three phase arc display at
the 1939 NY world's Fair. Although they were
billed as "Million volt" transformers, the
leakage inductance of the transformers made them
function like giant self ballasting NSTs,
according to the retired GE employee I once
talked to about them. They were driven by big
motor gensets onsite, rated for a great many
horsepower. It was the high current available to
them that made the spectacular continuous arcs.

Dave

Tesla list wrote:
>Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>
>
>Hello List,
>
>I am considering purchasing a Big box x-ray
>transformer, somewhere near 100kv at >150ma
>single phase 240v 60hz for a large Jacob's
>ladder. What has been anybodies' experience with
>these? It is presently DC out but I would remove
>the diodes and filters and put a flat plate on
>top with (2) 14,400v horns on it. Evidently
>others are doing this without arcing to the grounded case.
>
>Here's the question: how big of arc could I
>expect to draw on a dry, windless night. I have
>not been able to get much more the 12-14" with our usual 14400 driven hard.
>
>.A bit off topic, but hopefully of interest.
>
>Thanks,
>Jim Mora
>
>