[TCML] VTTC geometries, opinions needed

[bartb]

John,

Thanks for this info as it applies to me as well (good timing). I was 
sort of planning on winding square #8 magnet wire on the acrylic itself. 
Sounds like a potential problem depending on heat and something I can 
now divert around.

Thanks,
Bart

Dr. John W. Gudenas wrote:
> 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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>
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