Re: Two layer primary

["Barton B. Anderson" <tesla123-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Gary, 

Tesla list wrote: 
>
> Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> 
>
> I would like to rebuild my primary as a two-layer flat pancake.  The reasons 
> for this are: 
>
> 1) I am also increasing my secondary inductance so that I can 
> correspondingly increase my primary inductance to achieve a higher surge 
> impedance and hopefully further lower my gap losses. 
>
> 2) The required higher primary inductance would make a single-layer primary 
> too large in diameter to fit the confines of my base assembly. 
>
> 3) By making a two-layer primary, the same inductance can be achieved with 
> fewer feet of tubing, thereby further lowering primary losses.

It all sounds good. 
>
> I'm drawing a blank on how to begin this construction.  The two layers will 
> be joined at the center, so the two terminals will be at the outside of each 
> spiral.  This means that the full primary potential (and much more if there 
> are unused turns!) will be present across whatever gap separates the two 
> spirals, so extra care must be taken to insulate against surface flashovers.

Why not connect the inner of the lower to the outer of the upper? This would
relieve about 1/2 the potential and decrease if all turns are not used (volts
per turn). I don't know how far apart your planning to seperate the windings,
but it wouldn't take too much to not have to worry about flashover thereby
needing no insulation between. 
>
> Obviously a Lexan plate must be built between the layers, and there can be 
> no holes through this plate, as I suspect a flashover will find such holes. 
> The no-holes rule complicates plans to mount the two spirals.  I don't like 
> the idea of gluing - it's potentially messy, and mistakes and changes are 
> made and glue is kind of permanent.  Short of using two back-to-back 
> insulating disks with holes that are offset, I'm short of good ideas. 
>
> Has anyone done this before, and can you point to any URL's that illustrate 
> how it was done?

Not I. 
>
>   
> Gary Lau 
> Waltham, MA USA

Take care, 
Bart