Re: Terry's DRSSTC 6000 BPS testing

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Jimmy,

At 12:03 PM 5/7/2005, you wrote:
> .................
>
> So you could get 20% more with 25 300uS bursts at 6000bps than 300bps at 
> 500uS?

Yes.


> Where'd you come up with those numbers to start with?

The coil does not produce longer streamers in the normal mode past ~300uS 
for T1.  They just get hotter.  More than about 15 breaks does not seem to 
increase streamer length either.  So I was just going off past experience 
and guessing where to look.

> It's hard to
> compare the numbers on a "Freau Number" basis, because you're only
> doing a single burst pretty much.

In the good ol' days, energy was easy since it was fixed by the primary 
capacitance and voltage.  The DRSSTC can add energy during the pulse.  At 
6000 BPS, we also have left over energy from the last bang...  So the 
concept of bang energy has gotten very hard to define let alone measure now....

> I guess the best way to compare it
> would be spark length/peak IGBT temp. At 4ms, it might sink quite a
> bit of heat into the case, but I don't know if it'd still be better to
> go with one big bang, or possibly a few bigger bangs.

?  But everyone uses different IGBTs...  Mine are just 1/4 inch on a side 
(die).


> What IGBTs are you using? I tried to come up with a thermal time
> constant for IRG4PC40W TO-247 IGBTs (ones I'm using) from the
> 'transient thermal impedance' chart. I came up with a little over a
> mS, but it's tough to tell, because different points on the linear
> portion of the curve still give different numbers. If the time
> constant is ~1mS, then maybe the best is 1000 peak bps, with larger
> bangs.

http://hot-streamer.com/temp/irg4pf50wd.pdf


> > At 05:25 AM 5/7/2005, Steve Conner wrote:
> >
> > >>The 6000 PBS burst mode seemed to produce roughly 20% longer arcs than
> > >>the standard mode.
> > >
> > >At a cost of how much extra power consumption though? In other words what
> > >was the "Freau Number" (spark length divided by square root power
> > >consumption) for your coil in 6k bps pulse mode compared to say standard
> > >200 bps?
> > >
> > >I would bet that it is less efficient (lower Freau number) at 6k than at
> > >200, otherwise our theories on streamer growth are all wrong.
> >
> > The average time energy was far less since there is a 1 second pause
> > between bursts.  It is difficult to know the actual burst energy since they
> > are not discrete burst but rather a train of bursts joined together.  I am
> > sure it can be figured out, but I have not worked it.
> >
>
> Try measuring the electrolytic voltage before and after.

I think we need to work out some way to deal with how we compare 
power...  Many things affect this in the DRSSTC.  Maybe Kill-a-watt meters 
but not everyone runs off 120VAC at less than 15 amps...  I think Steve 
Ward and I have both run at about 200 primary amps but his streamers are 
longer due to the coils configuration and element values...

Cheers,

        Terry