Hi ‘undisclosed’,
The typical voltage/current levels associated with the output of virtually any type of x-ray power transformer are not very suitable for driving a classical spark gap fired Tesla system. A typical dental x-ray transformer’s output voltage will generally be ~70 kV. Voltage levels of this magnitude would require herculean efforts to suppress corona formation (and unwanted flashovers) and also require a very robust (and expensive) primary capacitor to withstand such potentials. Also, it’s rated output current of 10 mA or less would face a significant challenge in being able to FULLY charge a primary capacitor of more than say 5 nFd worth of C within the time frame of the mains AC half cycles. I suppose since most x-ray trannies are non-current limited, with careful input ballasting, you could overdrive its core to extract considerably higher output current levels than its nameplate rating, with a reciprocal drop in its output voltage as well, within reason. Spark gap driven coils work best with primary circuit voltages in the 5 – 20 kV range. At lower voltages, the SG won’t fire reliably, at higher voltages, corona standoff becomes an issue.
X-ray trannies make for great really high voltage capacitor chargers or huge Marx bank drivers (with the internal diodes left intact) or Jacob’s ladder or lightning screen props (with the internal diodes removed), but Tesla coils are best powered by the likes of OBITs or bug-zapper transformers (for small coils), old style, non-GFI NSTs (for small to medium sized coils), and BALLASTED MOTs or PTs (for medium to fairly large coils), or pole pigs (for REALLY large coils).
David Rieben
Sent from Mail for Windows 10
From: undisclosed recipient via Tesla
Sent: Thursday, June 29, 2017 8:51 PM
To: Tesla Coil Mailing List
Subject: [TCML] Words of wisdom
I built my first coil and made a halloween prop out of it ( a witch shooting arcs out of her hands ).
This year I might make it a Harry potter’s wand.
However… I’m looking at a dental XRT (x-ray transformer) to power my next coil project… any advice?
I already have an 800 watt MOT as the ballast.
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