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Re: Tesla!

Well, I mounted my 4 microwave oven transformers on a board, wired 
everything up (making sure everything was phased properly), and gave 
it a try at full voltage last night using a simple Jacob's ladder.  Since 
the voltage was only 8kV, I had to get the wires pretty close together 
before I could get a spark, but once it caught, the arc stayed intact until 
the wires were about 2" apart.  The actual arc length was probably 
closer to 4" or 5" since it formed an inverted 'V' shape before it broke at 
the top.

I definately need to set something up to limit the current before I can 
use this setup; using a single pair of transformers, I checked the 120 V 
current while drawing an arc and my 25 Amp meter was pegged.  Since 
I was running everything off a 10 Amp variac plugged into a 20 Amp 
circuit from the breaker box, I only tried this a few times.

I also discovered that my RF chokes that I have been using turned into 
nice resistive heaters with that much current pumping through them.  
After drawing an arc for 1 or 2 seconds, the coils were almost too hot to 
touch.  Also, I'm not sure why, but my chokes were hissing and making 
almost as much noise as the arc was!?  After that, I looked it up and 
found that the 18 gauge wire I had used to wind my RF chokes is only 
rated to carry 6-10 Amps.  Since I have never had more than about 
900W worth of transformers plugged in, I didn't have to worry about it 
until now.  Now I'm going to redo my RF chokes with 10 gauge wire 
(which is rated to carry 35 Amps and should hold me for a while).

And back to current limiting...I have a pair of 20 Amp variacs that I can 
hook up (one wired in normally to control the voltage and the other in 
series as a variable inductor to control the current), but I would rather 
not use my second variac to control the current if I can help it (has 
anyone ever tried this?).  One question that springs to mind is how big 
is a choke that would limit the 110 V current to 20 amps (i.e. - is this 
something that I can make easily using 10 gauge wire and a simple 
iron-wire core)?  Alternatively, is there anything else comercially 
available that doesn't cost a lot of money that I can use?


Steven Roys (sroys-at-radiology.ab.umd.edu)