Re: A Little more than general questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ghunter31014-at-yahoo-dot-com>

Good Questions!

I'll take a stab at them though.

If you increase the diameter of the secondary without
changing any other parameters, then you'll use more
wire, which will cause a modest increase in
resistance.  This ohmic increase is negligible, and
can safely be ignored for hobby purposes.  Increasing
the secondary diameter will have other far more
important effects.  For example, the operating
frequency will go down, the inductance will go up, and
the Q of the secondary will change.

There's nothing magical about a 1000 turn secondary. 
It's just a ballpark figure that works well for most
coilers.

Primary style is more than just a cosmetic choice. 
Flat spiral primaries give the lowest coupling,
conical primaries offer somewhat tighter coupling, and
cylindrical (helical) primaries provide the tightest
coupling of all.  Tesla coils require loose coupling
for proper operation.  Tightly coupled disruptive
coils are more likely to experience various problems
such as racing sparks, excessive spark gap heating,
poor quenching, secondary to primary flashover, and
weak spark output.  From a construction standpoint,
the flat spiral is simple to design & build.  The
helical primary is also very easy to make because it
can be wound on any convenient cylindrical form such
as a plastic Rubbermaid container, cake keeper lid,
etc.  The inverted conical is somewhat more
complicated to build.

How many primary turns?  You need enough turns to be
in tune (with the secondary) with the smallest tank
capacitor you anticipate using with that coil.  So you
need to decide ahead of time what your smallest-ever
tank cap size will be.  At the other extreme, you need
at least one full primary turn, so you can't use a
tank cap so big that you will need less than one full
primary turn to be in tune.  As the tank cap gets
smaller and the number of primary turns increases,
spark gap losses decrease and overall system
efficiency increases.  On the other hand, a bigger
tank cap gives a bigger bang size (assuming your power
supply is stiff enough to charge it), so it's a
compromise.  Many coil gurus swear that a tank circuit
using a smaller tank cap and a larger number of
primary turns yields a better performing coil.

Hope this helps,

Greg
http://hot-streamer-dot-com/greg

--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Wade B AndB Anderson by way of
> Terry Fritz <twftesla-at-uswest-dot-net>"
> <nabedaw-at-juno-dot-com>
> 
> Hi folks,
>   I am going to turn my questions to the primary and
> secondary windings.
> 
> By increasing the diameter of the secondary coil, I
> will increase wire
> resistance, that is a gimme. In what ways does that
> affect the coil
> operation???
> 
> Why is 1,000 turns of wire the magic # for this
> coil??? Of course if the
> turns are increased or decreased the inductance is
> affected, as would be
> the inductive reactance, as is it's ability to
> establish a magnetic
> field.
> And of course the secondary voltage is directly
> related to the # of turns
> in relation to the primary.
> 
> My question is, what effects ( to the operation of
> the coil) would result
> if the turns are say.... doubled, or halved???
> 
> On the primary coil how many turns would you all
> recommend??? Maybe a
> ratio to the secondary??? 
> And at what spacing???
> 
> >From what I can gather from previous responses, it
> sounds like that a
> flat or coned primary is just a matter of
> preference??? Is there a
> different affect if the primary windings actually
> surround the secondary,
> other than the fact that one may risk damaging the
> primary with secondary
> strikes.
> 
> Thanks, all of your comments are very helpful;
> 
> Wade
> 
> 
> 


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