Re: SSTC not working as expected

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Rob,
        Low powered bench expts I've done indicate that driving a TC 
primary is definitely superior to bottom feeding. It is an impedance 
problem. The real problem is that due to a less than infinite output 
impedance, the base impedance of the resonator is well above zero 
Ohms. This is one reason why running a resonator from a classic pri-
sec arrangement in a disruptive TC works so well. I'm not saying that 
what you're doing can't be made to work - it can as others have 
demonstrated. It's just that you need a considerably greater steup-up 
ratio to get your driver's output impedance more in line with the 
base impedance of the resonator. Even there it doesn't end - the 
moment sparks start issuing from the top of the resonator. the base 
impedance leaps upwards as it would in any previously "open circuit" 
1/4 wave transformer with a load applied to the far end. Useful for 
input power limiting I suppose.

Regards,
malcolm


On 5 Jun 2002, at 12:39, Tesla list wrote:

> Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<rob-at-pythonemproject-dot-com>
> 
> Here is my setup:  
> 
> 1. 18" of #26 on 4.5" form with 8" semi-sphere on top
> 
> 2.  160V applied to latest generation IR IRFP50LC 600V reduced gate
> charge MOSFET, in a flyback configuration. A 100pF-500ohm snubber is
> used.
> 
> 3. TLC555 oscillator with UC2710 6A driver, coupled to MOSFET with an
> isolation tranformer.  I get very square 8V p-p on the FET gate.
> 
> 4.  Output tranformer is 10 turns primary, 30 turns secondary, which
> then bottom feeds the coil.  This tranformer core only gets hot after
> very long use. It is 1.5 sq cm core area.
> 
> I get lots of RF voltage out of the tranformer.  Enough to create a very
> small arc with a screwdriver.  Yet hardly any output from the coil. 
> I've checked it with a scope and I  appear to be applying voltage at its
> resonant freq.  It lights up a neon bulb quite a distance away, but no
> streamers at all.
> 
> Perhaps it is a matching problem.  I will see if I can come up with the
> S-Params with the Ansoft Serenade eval version.  The FET only gets
> slightly warm, so it appears that little energy is being coupled into
> the SSTC.  I may have to just go with a primary SSTC winding instead of
> the bottom feed.
> 
> Rob.
> 
> 
> 
> -- 
> -----------------------------
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> 
> www.pythonemproject-dot-com
> 
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