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Re: xray xfrmr powered coils



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Justin, Frank,

I understand the dilemma (an age-old problem). But the transformer can be put to good use. Variac the input voltage to 1/2 power for 30kV out. This is actually a nice voltage to use and wouldn't require too many details beyond the norm other than ensuring the cap is rated accordingly, power needs are met, and the variac max voltage is mechanically stopped. This is an 18KVA transformer, so I assume it's inputs are 240VAC. With a variac at 1/2 power, you'll need to allow for 40A input levels, but that isn't really a big deal for a coiler.

I wouldn't mind having that type of a problem (smirky grin).

Take care,
Bart

Tesla list wrote:

Original poster: Frank <fxrays@xxxxxxxxxx>

Hi Justin,
I have had 2 old X ray transformers, oil filled and pack a punch! Still have one and wondering what to do with it. It weight about 400 pounds and 22" square by 18" tall. it is from the 20's.

I was going to try and build a TC around it and gave up. First problem is finding a cap to withstand that kind of voltage. The only way to get one would be to make an oil filled one and it would be huge to withstand the voltage and give the required capacity.

You would be inputting a crude guesstimate of 18KW into the coil which requires very special construction, insulation and large diameter conductors, not to mention very high cost for specialized materials.

Not saying it cannot be done as Bill Wysock certainly is one of the best at fabricating such a coil!

Lastly, operating such a coil would require wide open spaces, very secure and proper safety precautions, interlocks and planning. The RFI from such a coil would be enormous.

You would be better building a coil with a lower input voltage higher currents, a 15.5 KV transformer at a 20KVA rating would give the same results with less critical components. All the other requirement for safety and etc would be unchanged.

Coils of this power will not give seconds chances if you get stuck by them and components can blow up with serious results.

Frank
At 09:54 PM 2/20/2007 -0700, you wrote:

Original poster: Justin <rocketfuel@xxxxxxxxxxxxx>

Hi all,

I built my first coil around a pair of 12kV NSTs and am now thinking
about building something a little bigger.  I've come into possession of
an x-ray transformer that outputs +/- 62.5kV at 300mA (with 240V in) and
I'm wondering how best to harness the power.

Of course it will need a choke to limit current, but what I'm wondering
about is what primary circuit voltage to try to design for.  I seem to
recall seeing something about bang energy being related to the square of
voltage, so doubling voltage should quadruple the bang energy, right?
But then there is the problem of insulation.  I would think the primary
turns would need to be spaces farther apart to prevent inter-turn arcing
as well as the spark gap.

Is there any general rule of thumb for highest reasonable voltage to run
the primary at?


Thanks!


Justin in Austin