Re: [TCML] first coil help - BartB

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Thomas,

Sorry to get to this late. I have a lot of family visiting at the moment.

The coupling coefficient (k) is a ratio representing how much of the 
primary coils electromagnetic field is coupled to the secondary coil. 
This coupling also represents how fast the energy in the primary tank 
circuit will be transferred to the secondary. The higher coupling is, 
the faster this transfer occurs. Problems begin to be seen at k values 
above 0.18, but many coils will see problems at lower k values. 
Typically, about 0.12 to 0.15 is good. Problems normally seen are racing 
sparks down the secondary.

You can measure or use programs like Javatc, Acmi, MandK, and Inca.

Take care,
Bart

Thomas Ryckmans wrote:
> Hi Bart,
>
> What should I know about k? Is it, roughly, the ratio of energy transferred
> from primary to secondary? I have Mitch Tilbury's "The Ultimate Tesla Coil
> Design and construction guide", but while there are equations to calculate
> k, I still don't know exactly what it is...
> Shall I aim for a k as high as possible?
>
> Am rewinding the primary as per your instructions but it is going slowly
> (making a new base, a new set of primary support, a way to vary the height
> of the primary wrt the secondary) - I wish I had more time...
>
> Many thanks
>
> Thomas
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
> Of bartb
> Sent: 24 March 2008 03:02
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] first coil help - BartB
>
> Hi Thomas,
>
> No problem. Thanks for letting me know. Certainly makes a difference and 
> your numbers now do end up at 15 turns/cm.
>
> Something I noticed however, the distance from the bottom of the 
> secondary to the edge of the beginning of the primary looks to be about 
> 5.5cm which is wide and makes for a low coupling of 0.08 along with the 
> primary about 1cm below the secondary? I would recommend raising the 
> primary to where the primary is 3cm "above" the secondary which would 
> put k at 0.123. That seems extreme, but it's not with your geometry. 
> Should tune in at about turn 3. It would be nice if you could use a few 
> more turns out of the 8.4 you have now, but due to the situation you 
> really can't. Normally I would say get rid of all those extra turns as 
> it is a little extreme, but the fact is those extra turns add some 
> external C to the coil and allows more turns to be used. So I would just 
> leave them alone for now.
>
> It would be nice to rewind the primary if possible starting the primary 
> at about 2 to 2.5 cm away from the secondary and then setting the pitch 
> to 13mm (center to center) or basically where the spacing edge to edge 
> equals the wire diameter. No need to have such large spacing between turns.
>
> Spark gap needs some work, but you already know that.
>
> Take care,
> Bart
>
>
> Thomas Ryckmans wrote:
>   
> > Bart,
> >
> >  
> >
> > Really sorry to have wasted your time; the diameter of the secondary is 70
> > mm not 130 mm. 
> >
> > Using the inductance calculator here
> > http://deepfriedneon.com/tesla_frame6.html
> >
> > I get 3.2 uH with Diameter=70 mm, 480 turns, 15 turns/cm, 32 cm height
> >
> >  
> >
> > Really sorry
> >
> >  
> >
> > Thomas
> >
> > _______________________________________________
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> >
> >   
> >     
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