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Re: DC power

> Is there anyone out there running a large Tesla coil (in the 2 kva 
> range) on DC power?

There was "member activity" article in the TCBA newsletter a year or 
two back that featured a DC powered coil.  The primary was powered by 
a couple of microwave oven transformers that were rectified and run 
through a voltage doubler circuit (if my memory serves me right).  
There was also a lot of inductive ballast used to keep the xformers in 
line and I seem to recall discharges in the 30"-40" range.  If you're 
interested, I'll find the year/volume reference for you.

I've been wanting to try some DC experimentation also. One interesting 
feature about DC is that you can use practically any HV-DC supply with 
a very large primary capacitance since you don't have to charge your 
capacitor to breakdown voltage in the 1/120 of second available before 
an AC supply would reverse polarity.  I've seen this described as an 
"Impulse Tesla coil", but I have no idea how it would perform.  I would 
imagine that a low-rep rate, extremely high current pulse from a large 
capacitor in the primary would give some interesting effects from the 
secondary.  I would also imagine that quenching could be problematic.  
This might be a good candidate for a bi-polar coil with a single turn 
primary?  One thing to remember is that with a DC supply, your 
capacitors WILL be charged to a lethal voltage when you turn the power 
off.

*******************

Has anyone read the book from L. Anderson reviewed in the last TCBA 
newsletter about one of Tesla's "lost" lectures?  The review talks about 
(relatively) long sparks with only 10 VA input!

Well, hamfest season is upon us again.  The first large show in my 
area was this past weekend and a good time was had by all.  I spent 
the better part of Saturday lugging around about 60 lb of what I though 
were high voltage transformers, only to get home and find out that one 
was a 30 pound boat anchor and the other was an isolation transformer 
(120V in - 120V out) good to 40 kV isolation.  Oh well.  On the brighter 
side, I found that used RG8 solid core coax was very cheap (I got about 
a hundred feet in various lengths for $8).  A lot of people had it for sale 
and there were some who were practically giving it away!  I also picked 
up some RG9B - it looks similar, but I'm not really sure what the 
differences are.  Any input as to what the numbers really mean?


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