Re: OLTC update - primary IGBT loss

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

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

Hi Paul,

At 09:05 PM 9/4/2002 +0100, you wrote:
>Terry wrote:
>> Wonder what happens if one refires 180 degree off from the present
>> ring...  That should send some shock waves up the secondary ! :o))
>
>Oh, what madness is this!
>
>I modeled the situation where: just as the primary energy is
>momentarily zero at the peak of the first beat, we re-stock the
>primary cap with another bangs worth of energy (eg by switching
>to a second cap bank - one that you charged up while the 1st bank
>was going through its first half-beat).
>
>The normal ringdown, without quenching, is 
>
> http://www.abelian.demon.co.uk/tssp/tmp/tfoltc-c1.gif
>
>and the double-bang event is in
>
> http://www.abelian.demon.co.uk/tssp/tmp/tfoltc-c2.gif
>
>The second cap is switched in at 50uS.  Following this, instead
>of the secondary energy ringing down, it does another cycle or so at a
>slightly higher Vtop.  Note that the Ipri and Vpri don't exceed 
>their original values, so no extra device stress.  The follow up bang
>roughly doubles the number of cycles that the secondary could be
>extending streamers over.

It appears that the SonoTube will not be transmuted into gold bullion from
this exercise ;-))  However, the possibility to change very pure silicon
into a molten blob of SiO2 is high.  We'll just forget that one ;-))) 

>
>> I need to try wrapping another coil to see if that affects
>> anything like Antonio suggested.
>
>Well if you do, ping the coil before and after so we can see how much
>it changes.

Darn..., got too late tonight to do this :-(

>
>> I did not retune the coil for the added probe C since I didn't
>> want to fiddle too much
>
>Yeah, that's fine.  I don't care what the tuning is, so long as it
>stays put.  It's a major ball ache to recompute everything if something
>is shifted.

Yeah,  Don't wan't to go changing too many things at one time.  Models
don't care if it is out of tune...  They still work anyway...

>
>> Is a pin point OK?
>
>Depends what we want to know.  My particular interest is in witnessing
>the expected 26kV/cm surface gradient in action, and to observe the
>extent of the topvolts clamping action.  For that we need a predictable
>breakout surface, so a point is out.  I can manage with a small ball,
>or a rod with a smooth hemispherical tip.  The rod or ball must be
>vertically above the axis of the coil/toroid so that the whole system
>has cylindrical symmetry.  Single shot only for now.

I could not find any really good stuff for this.  So I ordered up some
threaded brass balls from MSC.  1, 1+3/8, and 1+7/8 inch diameter.  1/4 and
3/8 inch thread to match my stuff.  Next week...  My other post tonight
shows that I can see breakout and streamer formation to a very high accuracy.

>
>But then if we simply want to know whether streamers evolve over 
>part of a cycle, a couple of cycles, or several consecutive bangs,
>then any old breakout point would do I suppose.  

But real ROCs are best.  Best to eliminate as many variables as possible
there!!!

>Don't need a topvolts
>measurement for that, just the current to the breakout point, along
>with Ibase.  

That is toooooo easy!!!!!! ;-)))

>We might find that we can go a long way just on that
>basis, eg we can integrate the breakout current to see how much charge
>is upheld.  We can tabulate upheld charge with observed streamer length.
>We can also look for signs of streamer evolution preferentially on
>one polarity.

That be the negative polarity ;-))  Bandwidth is a problem.  I can go to
40MHz on the streamer current and 20MHz on I base.  I hope Ibase is well
and fine.  But I worry if 40MHz is good enough for Istreamer...  Maybe HP
has higher speed optics now...  Doubtful, since Carly has totally nuked the
HP place >:-((    Maybe the Chinese have a higher-performance replacement... 

>
>Either way, tons of stuff to go at.

Oh!!  You think secondaries were fun!!!   Steamers... we're talking fire
now!!!!!!!  :o)))))))))

Cheers,

	Terry


>--
>Paul Nicholson
>--
>