Re: X-Ray Transformer HV Power Supply

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

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

In a message dated 5/5/03 6:13:22 AM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

>Just wondering if anyone had experience with HV X-Ray Transformers and
>building power supplies / capacitor chargers with them.  Due to their much
>higher voltage, power supply construction will have many more difficulties
>and complexities than a supply built using a transformer with 10-40kV output
>- i.e. oil-submersed, higher voltage parts, etc... What are your
>experiences???
>
>Thanks
>The Captain


Captain,

I have a 140 kVP, 500 mA x-ray transformer that tips the scales at
nearly 1000 lbs. and I am just using it to drive a wicked Jacob's lad-
der. It had the rectifier assembly inside it when I got it but the recti-
fiers quickly burnt out when I started shorting the outputs, even with
the input to it well ballasted. I finally had to pull the core out the tank
and take out the rectifiers and just use it as an AC HV supply. The
diodes that come in these x-ray trannies are very physically small
for the > 100 kV at several hundred mAs that they can put out. Of
course they are designed to be submerged in oil during operation
and for very low duty cycle (usually < 1 second for the x-ray expo-
sure). It seems to me that you would almost have to have your rec-
tifier assembly submerged in oil just like the transformer but that
it would require a considerably more robust rectifier for continuous
power supply/ and or capacitor charge duty. I have 11 of those 5 kV,
2 amp hockey puck style diodes that I am currently using (all of them)
as  rectifier for my (2) seriesed 7200 volt PTs that I use to charge my
(2) 10 kV, 100 uF coin shrinker/can crusher caps. I think this style
of diode would probably work for rectifying an x-ray trannie's output
if you had enough of them (like at least 40 per leg) and they were al-
so submerged in oil.

One thing you need to be well aware of when dealing with x-ray trans-
formers is that their output voltage is very high and has enough current
to be EXTERMELY DANGEROUS. Mine will easily jump the ~ 8" gap
at the nearest approach of the sparking rails of my Jacob's ladder and
as I run the variac up, it begins corona hissing like 100 angry rattle
snakes before the 8" gap finally breaks down. This hiss sounds quite
wicked and could also be compared to the sound of frying bacon. I can
actually feel the "electric wind" in my face or on the back of my hand
through the grounded chicken wire cage around it when the voltage is
turned up to the point just before spark breakdown between the Jacob's
ladder rails (probably at least 2 ft. away from the nearest HV terminal,
with the grounded chicken wire cage between me and the HV terminal)
This is certainly not for your beginner HV experimanter ;^0

Be safe,
David Rieben