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 03:18 PM 9/3/2002 +0100, you wrote:
>
>The question now is whether these low Q factors lead to low power-to-
>streamer efficiency, which in turn depends on how quickly the streamers
>form.  Do they take a quarter-cycle, or maybe a few cycles, or does
>it require repeated bangs?

That certainly appears to be a big factor here!  I may have lots of instant
voltage but not enough energy to sustain the power to feed a big streamer.

>
>Those questions lead us to where the tssp project is right now. We need
>to get that topvolts probe sorted out.

You know, electronic OLTC coils can operate at very low levels with high
accuracy and repeatability (no spark gap to jump).  Perhaps instead of
getting a probe to measure 500,000 volts, we need a coil that can go down
to 60,000 volts...  :-)))  One could then do real time streamer voltage and
current (might be a sort of small streamer).  One would have to time shift
the current signal to allow for propagation delay in the glass fiber optics
(~30nS).  Also the voltage probe would have a little capacitance loading.
Would be interesting.  If I had three channels I could do base current at
the same time.  One very nice thing about the OLTC is that there are no
high voltage drive circuits, everything in the primary side can easily be
directly probed.

>
>Can you use a fibre-optic current probe between topload and breakout
>point?  That would give us the streamer current.  We could at least
>see where in the RF cycle the streamers are taking current.  

Sure!  Tonight I'll work on such things.

>
>I'm having trouble modeling your triple parallel turn primary - the
>interaction between the three is not modeled by the tssp software and
>they are too far apart to model as a single turn.  This is why I 
>haven't sent any V/I profiles.

The three turn primary was nice in that it gave lower Lpri.  But from a
theoretical and modeling point of view, it sure is a pain.  I wonder if
coupling in three spread out rings hurts the waveform on the secondary.  A
point source would be best.  Three rings may be like trying to set up a
standing wave on a rope with three people holding onto it shaking in unison
but in different places.  Maybe it could be modeled by superposition where
you do each one and then just add the numbers.  Not sure...  A messy
problem.  You don't need to worry with it unless you really want to.

Cheers,

	Terry


>--
>Paul Nicholson
>--
>