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[TCML] VTTC geometries, opinions needed

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

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!

Jim Mora

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