Re: Terry's DRSSTC 6000 BPS testing

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Terry,

On 7 May 2005, at 18:51, Tesla list wrote:

> 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....

It should be possible to calculate the total energy per bang from the
scope waveforms shouldn't it? As a starting point, for a disruptive
coil we could measure how much energy was actually transferred from
the primary cap to the secondary by taking the energy difference
between two successive beats as a percentage and extrapolating
backwards, knowing of course the original capacitance and firing
voltage. I'd be surprised if something similar could not be done in
this new case.

Malcolm


> >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
>
>
>
>