Re: OLTC update - A problem!

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

Original poster: "jimmy hynes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <chunkyboy86-at-yahoo-dot-com>


  

impedance of the secondary shouldn't have any effect on the output efficiency.
the impedance would have an effect on the amount of power for a given voltage,
but in this case the voltage driving it rises with the impedance. for a fixed
k, the voltage driving the secondary because it sees more turns. besides where
would the power go? with a ss spark gap you should be able to do better. i cant
see how impedance would matter, but i could be wrong. 

 Tesla list wrote:
>
> Original poster: "Terry Fritz" 
>
> Hi All,
>
> I retuned the coupling and all
>
> http://hot-streamer-dot-com/temp/OLTC08-28-08.gif
>
> on the OLTC and the performance was better but still not as I had hoped. I
> think I know why now.
>
> Using the output impedance calculation method at:
>
> http://hot-streamer-dot-com/TeslaCoils/Misc/impedance/impedance.html
>
> I came up with an output impedance for my coil of 2,044,989 ohms!! That is
> really high! My big coil is only 26500 ohms. So I think the coil's output
> impedance is too high to fry nitrogen the way we would like it too.
>
> Output impedance is governed by the Lsec and Csec ratio. So I think I need
> a smaller secondary L and a top terminal the size of a cow or something...
> I'll have to work on this... I was worried about this, but I didn't think
> I would make it this far so soon :o))! I suspect this problem plagues most
> low frequency coils. I was modeling the coil to run into a 220KOhm + 2pF
> streamer load which has a magnitude of 2,191,278 ohms so it "should" have
> worked from that point of view. Source and load "should" have been closely
> matched. But it looks like there are a few unknowns still out there ;-)
> With 286 watts in I should be able to get streamers of 28 inches according
> to John's formula. Much more considering I am not burning power in a spark
> gap. But either the low frequency (I note that I am at the frequency of
> Greg Leyh's Electrum which seems to come in a little low for streamer
> length given the input power) or the impedance thing is causing a problem.
> Probably time to get out them fiber-optic probes ;-))
>
>
> In other news... I designed in IGBT current tester. Here is the simple
> diagram:
>
> http://hot-streamer-dot-com/temp/OLTC08-28-06.gif
>
> Here is the messy one:
>
> http://hot-streamer-dot-com! /temp/OLTC08-28-07.gif
>
> It is basically a copy of a singl! e section of the coil. I played the
> values to get an almost perfect matching current waveform to the real one
> but I can push 600 peak amps here on a single IGBT (1200 amps with a slight
> modification!). I will probably use the coil's drive modules to run it but
> making another drive circuit is pretty easy too. With this tester I can
> run the IGBTs until they break and determine how hard I can push them.
> apparently nobody knows how hard IGBTs can be pushed in such case. Be
> interesting to see :-))
>
> The impedance problem is the first real "obnoxious" problem with the OLTC.
> But it is not a mater if an OLTC works now but rather how to perfect it ;-))
>
>
> BTW - For 50 Hz UK operation. the charging inductor needs to be:
>
> 50 = 1 / (2 x pi x SQRT (47e-6 x L)) Where L = 215.6mH Big ~6 to 10
> pound split core (E-core may be better)) that does not saturate given the
> current. I guess it could be designed for a saturable reactor if one were
> ! really good at that stuff...
>
> You need to watch that the peak value of the primary voltage does not go
> too high with the longer charging time and the line voltage you have over
> there. I can't think of anything else that would be affected. I am not
> sure my IGBTs can take 240VAC yet until I do the destructive testing...
> The IGBTs and stuff will be here Friday so I can do that this weekend.
>
>
> I should point out that this OLTC stuff is all brand new bleeding edge
> stuff and I am using a ton and a half of computer models and extravagant
> test equipment to get it to work. The goal is to make it very simple and
> easy, but right now the guarantees are zero for those that wish to try it
> themselves. Things have gone extremely well, but if you try it and have
> trouble right now, just don't blame me :o)))
>
> Cheers,
>
> Terry
>
>



JImmy



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