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Re: The RAT coil.



Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> 

Hi Finn, 

Yep, your right. The ripple isn't ring down and a resonance is a more likely
description. The overshoot occurs where the current along the AC cycle is
highest and therefore the cap charges to a higher voltage. But after that
break, the current may be heading through zero crossing and is at it's mimimum
charging current. Still, this an odd waveform in that it waits for such a long
time before the cap curves to a normal charging waveform. 

The ripple is occurring during this odd behavior and whatever is causing the
ripple, is the cause of the odd charging behavior. It almost looks like a
resonance opposition (reactance). 

BTW, I took a look at your primary photos. LOVED THEM! These pics will put all
kinds of ideas into the minds of coilers. I'm already thinking how to
incorporate something similar. This method of primary tuning could be carried
over to any type of primary (flat, coned, helical). The only problem that I see
is there will be a limit to power throughput, but maybe there's a way around
that as well. 

Thanks for putting the photo's up so quickly. 

Take care, 

Bart 

Tesla list wrote: 
>
> Original poster: "Finn Hammer" <f-hammer-at-post5.tele.dk> 
>
> Bart, all, 
>
> The overshoot was unsuspected from simulations, however it is a common 
> occurrence with , particularly, LTR designs running at 100/120 BPS. 
>
> Richie Burnett has an excellent description of the phenomenon here: 
>
>
> <http://www.staff.ncl.ac.uk/r.e.burnett/offset.html>http://www.staff.ncl.a
> c.uk/r.e.burnett/offset.html 
>
> The ripples that you see can not be from the ringdown, The trace is too 
> thich for that. Rather it must be some sort of resonnance btwn the 
> ballast and the MOT`s. 
>
> However, there is something fishy going on around just that particular 
> quench, because the cap starts out at a higher initial voltage there, 
> than at the other 2 ringdowns. Perhaps the effect of uneven electrode 
> spacing. I`l check that again before next run. Perhaps adjust trace 
> rotation on the scope too, it seems to be a bit off. 
> I have not yet had the time to view the ringdowns under streamer 
> loading, (the picture was taken discharging to a grounded rod, due to 
> space limitations)and apply delayed sweep to that portion, to zoom in on 
> details, but it is one of the first things that I will do, when I run 
> the coil again. 
>
> Cheers, Finn Hammer 
>
> Tesla list wrote: 
> > 
> > Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net> 
> > 
> > Finn, all, 
> > 
> > The overshoot is interesting. The cap continues charging to a higher 
> value then 
> > when it finally discharges, the later portions of the ringdown continue 
> > outward. 
> > You can see the ripple on your screen. I wonder if this poor quenching on 
> these 
> > particular points? 
> > 
> > Bart 
> > 
> > Tesla list wrote: 
> > 
> > > Original poster: "Finn Hammer" <f-hammer-at-post5.tele.dk> 
> > > 
> > > Richie, all 
> > > 
> > > Those flats,(which are the same flat, really, symmetric on each 
> > > halfphase) Have me baffeled too, something that I had not expected at 
> > > all. From simulations I had expected this: 
> > > 
> > >
> <http://home5.inet.tele.dk/f-hammer/msim.jpg>http://home5.inet.tele.dk/f-h
> ammer/msim.jpg 
> > > 
> > > The overshoot before the break at 2mS is also unaccounted for. I guess 
> > > that it has to do with some peculiarity of the MOT`s, and I am 
> > > speculating that these beasts actually are wound on a core that has some 
> > > sort of square hysteresis curve or something. This could perhaps be 
> > > tailored to the application in the oven, and also explain why they 
> > > perform so well in tube coils. They are sort of peaky in responce. 
> > > 
> > > Cheers, Finn Hammer 
> > > 
> > > Tesla list wrote: 
> > > > 
> > > > Original poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk> 
> > > > 
> > > > Hi Finn, 
> > > > 
> > > > This looks like a very flexible Tesla Coil,  and is beautifully built 
> too. 
> > > > It should provide an excellent test bed for your research,  I wish I
> had 
> > > > one ! 
> > > > 
> > > > I did some work with uneven spaced firings,  and the ability to adjust 
> > > > each firing point in real time is so valuable because there is a lot 
> > > > of interaction between each firing. 
> > > > 
> > > > I took a look at the charging voltage waveform shown on your page: 
> > > > 
> > > >
> <http://home5.inet.tele.dk/f-hammer/charging.jpg>http://home5.inet.tele.dk
> /f-hammer/charging.jpg 
> > > > 
> > > > The two flat portions in the trace are seem unusual.  I have never seen
>
> > > > this behaviour before,  and I usually have the scope connected when I
> run 
> > > > my coil.  Do you have any idea what is happening in these periods where
>
> > > > the voltage is almost constant ??? 
> > > >                                                         Cheers, 
> > > > 
> > > >                                                         -Richie, 
> > > > 
> > > snip