: One last question for anyone who might know about these 70kv / 100kv
: transformers from x-ray units.. This 70kv unit I have here; does this
: thing actually put out 70kv, or is that the rating after the diode
: rectifier?? I have no way of directly measuring these insanely high
: voltages, but with 60vac measured directly across the primary connections
: (using a resistive ballast) I can draw an arc about three inches long.
: Theoretically, that would be approximately 35kv (assuming 120vac gives the
: full 70kv) - and assuming of course the physical winding ratio is really
: 583:1!! Are these things really capable of 70kv (or 100kv)? Does there
: exist a xfrmr that really put out 100kv?? I seem to be getting mixed
: messages on the internet about this. Thanks again! -Wes.
Unlike most transformers (that are rated in RMS volts), X-ray transformers are rated for peak volts at a given current load. This is because the peak voltage rating reflects the maximum energy of the x-rays that can be created (which, in turn, determines penetrating power of the resulting x-rays).
The peak output voltage is independent of whether the output is rectified or filtered (unless a voltage doubling circuit is used). Rectification (with no capacitive filtering) will improve the duty cycle and thus the total x-ray power available. Adding a filter capacitor will reduce the "spread" between maximum and minimum x-ray energies, but again will not increase peak voltage.
The distance an arc will jump is really not a very good measure of voltage, since the distance you can stretch an arc is strongly dependent on the amount of available current. Heck, you can even stretch a high current low voltage welding arc for an inch or two.
The distance that a spark will initially jump between identical spheres is a considerably more accurate way to roughly measure peak output voltage. Here's a table that you may find useful:
Good luck and please remember to PLAY SAFELY - X-ray transformers can be VERY nasty!