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Re: Tesla!

Re: building a current limiting choke myself...I have references that I 
can use to get the formulas, I was just being lazy.  I think I'm going to 
use my variac until I can build something.  I'll just keep an eye out for 
old transformers to get the iron plates to use as the core.  There's a 
large hamfest coming up the second weekend in September, so I plan 
on picking up parts there.

Concerning the use of arc welders or transformers-I would have thought 
that the secondary would have to be open, not shorted?  All you want is 
a large enough inductor in series so the impedence at 60 Hz keeps the 
current below the meltdown level.  If you shorted the secondary, it 
seems that you would be drawing current limited only by the internal 
resistance or current-limiting construction of the transformer that 
you're using as a choke?  An early issue of the TCBA newsletter 
suggested using regular motors (1/3 hp, etc...) with the rotor removed 
in series to control the current, although I don't know what size wire is 
used in motors so I have no idea whether it could take 20 Amps without 
melting.  An alternative would be to rewind the motor with larger wire.

Another recent article in the TCBA Newsletter (the one about the DC 
Tesla coil built with microwave oven transformers) mentioned using a 
bunch of microwave transformers in series with the HV output to limit 
the current.  Another article in a previous TCBA newsletter was cited as 
a reference, but I don't have the issue mentioned.  If anyone else does, 
I'd appreciate a brief review of the article.  I don't know what issue was 
mentioned right now since I'm at work and everything else is at home, 
but the DC Tesla coil that mentions it was either in the last or the next 
to the last newsletter.


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