Robert Dwyer wrote:... Originally I thought to get a variac capable of reaching about 350 volts, and hooking it up to a transformer with a turn ratio of 1:100. Of course, I ran into problems thinking about how I would actually acquire a transformer of that ratio (I have looked everywhere to no avail). ...
It is refreshing to see a beginner embrace, instead of dodge, the learning-about-electricity step.
All DC voltage
sources have two terminals. Negative-hot just mean one that's running with its positive output connected to grounded stuff like the fusor, and thus safe to touch. Then only the negative output needs special insulation, and is unsafe to touch or even to get close to.
Regarding the transformer, you probably realize that the actual number of turns matters, not just the ratio. Otherwise step-up transformers would have one-turn primary windings. Magnetic saturation dictates the maximum number of volts you can get per turn. It's proportional to core area and operating frequency, and has nothing to do with load current. A 120 to 12,000 volt transformer (e.g. NST) would not work with 350 VAC input, it would instantly blow a fuse. Unless you increased the AC frequency to, say, 180 Hz. Then instead of core saturation, internal HV insulation failure would probably get you.
Here is one of my favorite tutorials on the topic: http://sound.whsites.net/xfmr.htm
One site with formulas right up front, if you want to dive into numbers, is: http://www.eevblog.com/forum/projects/t ... s-in-here/
For 35 kV and no voltage
multipliers, at mains frequency, the secondary windings have enormous turns counts and need special attention to insulation. Ready-made transformers of practical size are mostly those made for X-ray generators. Neon sign transformers are not made with high enough voltage
to do the fusor job easily.