high coupling -> racing sparks was Re: horizontal half wave (double ended) coil

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Original poster: "Jim Lux" <jimlux@xxxxxxxxxxxxx>



Subject: Re: horizontal half wave (double ended) coil


> Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>
>  > Original poster: Paul Nicholson <paul@xxxxxxxxxxxxxxxxxxx>
>  >

>  >
>  > It is well known that too much coupling tends to cause breakout
>  > in unwanted places, such as along the coil.  The speculative
>  > explanation above may be wrong or only part of the story, but the
>  > adverse consequences of high k are well established by coilers, as
>  > is the cure: reduce k.  The non-split bipolar doesn't offer much
>  > opportunity for k reduction without changing the primary dimensions,
>  > so maybe some off-axis inductance is the answer.
>
> Hi k causes more energy to be coupled in to the high order modes of the
> secondary and hence less in to the split fundamental frequency.
> The energy in the higher order modes may not contribute the spark
formation
> and or are dissipated more quickly. They are probably the major cause of
the
> start of racing sparks.
>
> The coupling problem can be solved relatively easily by having the center
> area of the secondary with no windings or an adjustable spacer between
them.
> This will effect the secondary frequency too unfortunately.
>


Another plausible explanation for high coupling (k) causing racing sparks is
that it causes the secondary topload voltage to rise higher.  A lower k
gives time for streamers to develop and absorb energy (which comes from the
top load), which in turn reduces the peak topload voltage.