Re: Primary inductance vs. coupling

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Jason Petrou by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jasonp-at-btinternet-dot-com>
> 
> Hi all,
> 
> Would a higher primary inductance allow much tighter coupling without
> overcoupling? My logic is that the RLC primary although it will ring at the
> same freq with a smaller cap and a larger inductor than previously it will
> take longer for the primary circuit to ring down, thus allowing a slightly
> slower rise in the secondary, allowing tighter coupling... or not :o)

The coupling coefficient depends essentially on the geometry of the
coils.
More or less turns make little difference.
If the coupling coefficient and the resonance frequency of the primary 
and secondary are kept constant, larger or smaller inductance
at the primary result in the same voltage and current waveforms
everywhere,
just scaled in amplitude.
There is nothing that can be identified as "overcoupling" in a Tesla
transformer. Excessive coupling can cause sparking between the two
coils, and maybe irregular voltage distributions along the secondary
that
can cause sparks in the secondary windings, but this has little direct
relation with the coupling.

> Also in case anyone's interested I am consistently finding that with higher
> breakrates I can increase the coupling... has anyone else noticed this?
> John, I believe you said something about this at one point...

Higher coupling reduces the energy transfer time, up to a minimum with
k=0.6, and asks for higher break rates. Maybe you have hit a point of
optimal energy transfer.

Antonio Carlos M. de Queiroz