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RE: [TCML] VTTC geometries, opinions needed
Say Doc,
Great advice. I will plan on using phenolic for my standoffs off the acrylic
(1" stringers). Most of the tubing will be in open air which should help
keep it cool. HDPE melts at a low temp I believe so that's now out!! Out of
curiosity, how many turns do you have at your tap point? First design
change!
Also keep in mind that 12awg is .0808". The tubing will be slightly more
than twice the diameter of 12awg at .1875" Though I will be running 4
tubes...
Thanks Much,
Jim
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Dr. John W. Gudenas
Sent: Monday, September 07, 2009 8:42 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] VTTC geometries, opinions needed
Jim
You are going to have a huge current in your primary. With my dual
833A VTTC and a 12awg primary that was
initially on a .125 acrylic form, I developed a problem. I melted the
primary acrylic form. Now, I did have long runs of 5 minutes or longer
while I took a lot of discharge pictures. Just be aware that many
acrylics have a very low melting temperature and your primary can get
hot.
Obviously heavier gauge wire will not get as hot, but it really wasn't
"that" hot. The acrylic just melted easy.
I did not run staccato but the 60 Hz continuous duty cycle and this
certainly will cause greater heat. I finally had a high temp. phenolic
form with a .5" wall fabricated for my primary to accommodate my long
runs and duty cycle.
I don't know what type of acrylic you have, but just be aware it can
have a very low melting point and your primary can get hot.
I really don't know if this is a problem for you, but it can't hurt to
keep it in mind.
John
John W. Gudenas, Ph.D.
Professor of Computer Science
On Sep 7, 2009, at 2:12 AM, Jim Mora 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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