Re: Primary tank cables

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

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br> 

Tesla list wrote:

 > Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au>
 >
 > Hi Coilers,
 >
 > I have just replaced my inadequate cabling on my primary tank circuit for
 > something a little more suitable.  It is not ideal because it is not
 > insulated for high voltage, but much better than it was.

Don't worry about insulation. Just keep the wiring suspended, away from
other things (and of course, don't touch it while in operation).

 > I am now using 50mm^2 double insulated 600V power cable.  Thick orange stuff
 > close to an inch thick with the insulation, and quite heavy too.  I have
 > been led to believe this cable is used for welding cable.  There are a *lot*
 > of strands of reasonably fine copper in the cable, so much better current
 > carrying capability than I had.

In a spark gap coil, the resistance of the wiring is not so important,
because the gap dissipates much more power that any reasonable wire
would,
and if the energy transfer is fast and efficient enough, most of the
energy is dissipated in the secondary system as streamers and sparks.
It's easy to show that the tubing used in most primary coils is,
electrically, overkill by a good margin. In most cases anything with
less than 0.1 Ohm of resistance is enough.
The wiring going to the power transformer is much less critical, as
the current there is really low.

 > It has improved my output quite substantially.  However my question is, how
 > does this affect tuning?  I don't believe I am correctly tuned anymore.

The effect should be negligible, unless previously you had really high
resistance in the wiring (maybe bad contacts?).

 > I
 > am wondering wether getting better power transfer would cause the  need to
 > move in or move out the primary tap point, i.e. does better power transfer
 > increase or decrease the resonant frequency of the pirmary circuit ?  I have
 > heard it can and does sometimes make a difference.

The primary tank must be tuned to the same frequency of the secondary
resonator. This is the best tuning even in the presence of heavy losses.
There is also a minor influence of the coupling coefficient
between the coils. There are several optimal couplings, but the exact
values are only important if the coupling is really high (>0.3). In
practice, the best is to look for the highest coupling that doesn't
result in insulation problems.

Antonio Carlos M. de Queiroz