Re: [TCML] VTTC geometries, opinions needed

["Dr. John W. Gudenas" <comsciprof@xxxxxxxxxxxxx>]

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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