Mini OLTC is getting 9"

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

Hi guys,

I just got my mini Off-Line Tesla Coil finished. Now that it has a proper 
power supply, it runs at 1200bps and produces 9" hot arcs to ground. It's 
been an interesting project and kind of ties in with what Dan "Captain 
Corona" McCauley was saying about the SSTC hybrid thing. Current is free 
but you pay for voltage etc.

The OLTC is kind of crippled by being restricted to about 700V primary 
voltage. You need a very large tank cap to get a reasonable bang size, so 
you have to use a one-turn primary and also a secondary with low resonant 
frequency, which means the secondary is physically large, so it has lots of 
self-capacitance and therefore a low top voltage and poor streamer growth. 
It also means the primary current is massive to the point that it isn't 
free any more. My coil runs 900 amps peak and the IGBTs get pretty hot as 
you would expect. They're probably about 60% efficient.

I put some spark pics from the OLTC as well as a quicktime movie on my website:

http://www.scopeboy-dot-com/tesla/t3sparks.html

Steve C.