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Re: Primary coil configuration



Original poster: "Krohns" <2halice@xxxxxxx>

Hi Gary,

Thanks for your input.   I'm glad I don't have to build a conical primary...
but I was willing.

You are correct... I had a PVC cap sitting in the middle of my primary in
the photo.  It was there to make sure that I was not off-center with my
primary windings.  I'm a perfectionist you know.  Before I do the final
assembly on the round board that my primary is mounted upon (which is
separate from the table top), I am going to cut a round hole in the middle
of it so that the secondary is mounted to the table and the circular primary
board is fully height adjustable.  The secondary also will be adjustable.  I
am going to cut down the PVC end cap, so its height will be reduced by half
and appy several layers of Lexan to its interior to insulate the pipe's
interior from current flow.

And concerning the amount of power I will be applying to the coil, I can
either run it at reduced power, or.... couldn't I raise the height of my
toroids to reduce strikes to the primary, or will raising the toroids height
cause the upper winding to emit streamers?

Hal in Tucson

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, April 20, 2006 1:19 PM
Subject: RE: Primary coil configuration


> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
>
> Hi Hal:
>
> How'd you manage to sneak an attachment past our moderator? ;-)
>
> I don't think there's ever any reason to use a non-flat primary,
> regardless of power supply or secondary size.  I've used flat primaries
> with my 2" 4/20 mini coil and my 6" 15/60 coil, and I can adjust the
> secondary height too low and get racing sparks or too high for not
> enough coupling, for both.  It all comes down to getting the right
> coupling, and NST and secondary size won't affect that to the point that
> a conical primary is needed.
>
> Speaking of coupling, after scanning your attachment for viruses, if I'm
> interpreting it correctly, it looks like you have a PVC end cap at the
> center of your primary for attaching the secondary.  This will force you
> to locate the lowermost secondary turn at least a couple inches above
> the plane of the primary, and this may be too high for optimum coupling.
> I've found that the lowermost secondary turn wants to be roughly even
> with the primary for optimum coupling, but one must always be prepared
> to experimentally go up or down from that point, so you'll need to find
> a means of mounting the secondary base below the primary base.
>
> With your 15/90 power supply, if you do a good job optimizing things,
> you may find that a 4" secondary is overpowered if you maintain the
> usual 5:1 secondary winding aspect ratio.  This will result in
> persistent primary strikes, and you'll soon want to build a bigger
> secondary, just to get the top load further away from the primary.
>
> Regards, Gary Lau
> MA, USA
>
>
>  > Dr. Resonance,
>  >
>  > I am building my first coil.  It has a 4" secondary.  Just this
>  > afternoon I wound a flat primary for it and then read your
>  > email.  Will a flat primary not work with 4" coils?  I plan on
>  > powering it with 15KV, 90mA.
>  >
>  > []
>  >
>  >
>  > Hal in Tucson
>  >
>  >
>  >
>  > ----- Original Message -----
>  > From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
>  > To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
>  > Sent: Wednesday, April 19, 2006 4:44 PM
>  > Subject: Re: Primary coil configuration
>  >
>  >  > Original poster: "D.C. Cox"
>  > <<mailto:resonance@xxxxxxxxxx>resonance@xxxxxxxxxx>
>  >  >
>  >  >
>  >  > If you run a 4 inch dia. sec coilform use a 15 or 20 degree
> inverted
>  >  > cone primary.  If running a 6 inch dia. sec coilform use a flat
>  >  > Archemedian (expanding) spiral.  Overcoupling is a big problem for
>  >  > most beginning coil builders and it generates multiple headaches
> like
>  >  > racing sparks, etc.  Keep it simple and it will work right the
> first time.
>  >  >
>  >  > Use 1.3 to 1.5 x Cres for your MMC cap value and you will have a
> nice
>  >  > performer.  The 6 inch dia. coil will give you better performance.
> V
>  >  > = -L x dI/dt.  Inductance, L, is proportional to the square of the
>  >  > radius of the coil so bigger is better.  Use #26 AWG for a 6 inch
>  >  > coilform and #28 AWG for a 4 inch coilform.
>  >  >
>  >  > With a reasonably large toroid, ie, 20 x 5 or equiv. modern
>  >  > transmission line theory doesn't apply much to TC building.
>  >  >
>  >  > Dr. Resonance
>  >  >
>  >  > >Hi All,
>  >  > >    I'm in the process of designing my first coil.  I'm a junior
> in
>  >  > > EE and it just caught my intrest while I was researching HV
>  >  > > transmission lines. I have a 15kV 60mA NST and I'm reading as
> much
>  >  > > as I can about the rest of the design before I actually
>  > buy/build anything.
>  >  > >    My question is what is the difference between making the
> primary
>  >  > > wind outward away from the secondary opposed to winding
> vertically
>  >  > > keeping the windings all the same distance from the
>  >  > > secondary.  Also what does primary placement around the secondary
>  >  > > effect.  If I move the primary up to the middle of the secondary
>  >  > > what will that effect?
>  >  > >
>  >  > >~Farmer
>  >  >
>  >  >
>  >  >
>  >  >
>
>
>