RE: Low Voltage Tesla Coils

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Richard,

Variacs have lots of head room so this does work, to a point (you'll "know"
when you reach it ;-)).  The high voltage will saturate the core pretty
fast.  However, who said we wanted a heavy expensive o'l variac either.
With a bit of thought in the control, we can fire at any voltage we want
just by timing when we trigger the IGBT during the primary cap charging
cycle.  No need for a variac, but just another few IC's (we trust silicon,
don't we? ;-))  Neat isn't it!! :-))  I suppose we could consider matrix
converters too, but lets not get too "far out", yet ;-))

But before you blow up a nice variac, consider this little circuit for
getting close to 700 VDC at !terribly! high power!

http://hot-streamer-dot-com/temp/Vx2.jpg

BTW - These direct AC line circuits involve giant power levels!!!  Your
grabbing the "power devil" by the tail...  Even pig system coilers will be
surprised by the explosions these circuits can make!!!  Don't forget fuses,
breakers, safety precaution, and getting far away if you dabble in such
things!!!  The circuit above does not show breakers, soft start, drain,
filtering, and a bunch of other very important "details"...

A fine bit of advice for dealing with direct line currents:

Imagine the side of your house where the breaker box is...
Imagine a six foot hole getting blown through your house there...
Imagine how far away you want to be when that happens..............

Another note:

I once asked a power engineer why the 12 Ga. line cord to his experiment
seemed to be rather small?  He replied...  It's the fuse......  3 hours
later, it proved to work...

I suppose LVTC's will require a number of "new" safety notes...

Cheers,

	Terry




At 08:38 PM 7/13/2002 -0400, you wrote:
>> One may even be able to go down to ~300 or ~150 VDC
>> (line voltage just rectified) and eliminate that transformer!!  An Off
>Line
>> Tesla Coil (OFTC - sorry again :-)))
>
>Terry, list,
>
>I've considered wiring a common variac as an auto transformer.  Probably
>dangerous as hell, but that's what we do the best, eh?
>
>Put the full 220 vac across one HV leg and the wiper of say a 1256D and
>take Vout from the other leg.  Would have to figure the lower limit of
>wiper travel and put in a mechanical stop.  Wouldn't want to put 220 vac
>and 150 amps across two windings.  Watts per variac wind could easily be
>calculated and wiper travel limited to a safe range.  After all, we all
>over drive variacs to 260-280 vac now.  What's a little more?
>
>Conceivably 500 to 800 vac could be available for your IGBT switched coil. 
>And, no heavy iron transformer.  
>
>Comments?
>
>RWW
>
>
>