Re: [TCML] VTTC geometries, opinions needed

[Steve Ward <steve.ward@xxxxxxxxx>]

I think the tank capacitance should be a good bit larger to make use of the
4 tubes.  I typically used 2nF for a single tube, so id suggest something in
the 8nF range for 4 tubes (really this is not an exact solution because
spark loading affects the tank impedance and thus the current through the
tank and tube).  But i do suspect that only 4nF will leave you with some
wimpy sparks compared to what it COULD do.  I guess it would be nice to try
some various capacitance values and see what really works the best.

Steve

On Mon, Sep 7, 2009 at 2:12 AM, Jim Mora <wavetuner@xxxxxxxxx> wrote:

> Hello Coilers,
>
> I am planning a quad 833C @ 4KW and have most of the goodies now (I have
> been rat holing for several years). For the secondary former I have a 36"
> .125" wall 6 inch acrylic tube. I want to wind it with 32 inches of # 21awg
> 200c wire. That amounts to 755 turns at 23.6 turns per inch. The coil
> should
> have a self resonance of 367.35hz. For a top load and more for shielding
> there will be a 7" .25" (rounded edge) plate which gives a total resonance
> 328khz using -20% with Javatc 9.1. Is that an error? I want to stay near
> the
> coveted 350khz resonance point.
>
> I have a few concerns: is 755 turns enough? I chose the wire to keep Fo up
> there and still have some coil height.
>
> The primary will be an eight inch acrylic .125 tube with a sliding grid
> feedback coil. The secondary (the unwound part) will go through the deck to
> be able to adjust the coupling on s screw of some type.
>
> I am under the impression the primary to secondary coupling should be close
> to k=.22 what is the max?
>
> There will be 1" vertical HDPE wind standoffs around the primary former and
> the winding will be 3/16 soft copper tubing spaced .2". So the primary is
> actually 10". The feed back coil will be above the primary and be 8" in
> diameter.
>
> I plan to use a total of .004uf mica cap array that gives about 15 turns of
> the primary. This gives a mutual inductance of about 220 and an inductance
> of ~59uh.
>
> The primary will be cool if it doesn't are over (which I think is unlikely)
> as it can be tapped the classic way.
>
> Any concerns or critics welcome. I will start the project this winter.
>
> Dr Spark, you are using a 2awg primary, yes? That is counter intuitive to
> me
> as I think we want higher impedances to match the high impedances of the
> tubes. What am I missing there? Having (4) in parallel surely helps this.
>
> My test transformer can deliver 10KVA at various voltages with a target FW
> @
> 4500v but weighs in about 200lbs. Good for setup and testing though!
>
> Thanks
> Jim Mora
>
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