Re: SSTC not working as expected

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

Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

Tesla list wrote:
> 
> Original poster: "Alan Sharp by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<AlanSharp-at-compuserve-dot-com>
> 
> Message text written by INTERNET:tesla-at-pupman-dot-com
> >I have been thinking alot about the traditional interupter.  An
> >excellent question is:  Why do you just get a small flame or streamers
> >CW, but giant discharges when using an interupter? <
> 
> Rob
> 
> sparking and blowing FETs - great :-)
> 
> The interupter lets me put more current through the FETs -
> if I tried CW the FETs would blow even faster. I reckon that the peak
> power is what matters.
> 
> I would have though that your driver transformer needs to be
> gapped in flyback mode but I've no experience of this. I would
> suspect that your FETs are dying of over voltage.
> 
> Alan

Hi Alan,  

I replaced the core.  I found a giant one in a flyback converter (500W
type).  And guess what, it wasn't gapped.  So I'm using it with no gap. 
25 turns of primary.  With 25 turns of teflon #24 ga I'm getting plenty
of corona and no blown fets.  I will gradually add more sections of 25
turns and see what happens.  I think you were right that the old
transformer was saturating from DC.  This core must be specially
designed for high DC currents with no saturation.  I looked at the FET
drain voltage on a scope.  It was 400 p-p AC, but due to measurement
difficulties, I don't know if it was sitting on a pedestal of DC.  I
need another 10x probe for my scope to do a differential measurement.

My PSpice sims show it in theory to clamp at 600V due to avalanche
breakdown of the source-drain diode.  I think these new generation FETS
from IR are repetitive rated for avalanche breakdown as long as the
current isn't too big.

BTW, I found a new way to take apart transformers (I used to boil them
in water).  Put the tranformer on top of one of those 500W halogen shop
lights util you smell melting varnish.  Then just easily pull it apart.

Sincerely,  Rob.


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