[TCML] Greetings from new coiler in Australia

[bartb]

Hi Dave,

My experience with safety gaps has shown me that it does need to be 
opened up wider than setting it across the transformer. If it is set the 
same as the main gap (same breakdown voltage), the two gaps will toggle 
and the hotter gap (safety gap) will start firing more and more often. 
It does need  to be set wider. How wide is difficult to say and a 
judgment call. If the cap is undersized for the transformer and running 
an rsg of some type, the cap may be charging to a higher voltage at 
breakdown. If say with a static gap the cap is sized for resonant 
charging, then again the voltage (may) be higher as determined by the 
main gap breakdown voltage. You can of course open the gap up until it 
stops, but if you go too far, then it's prevented from protecting the 
components. The margin of adjustment and protection is based on the main 
gaps breakdown voltage.

What your doing is normal and a couple mm should be fine. Think of it 
this way, if your main gap breaks down at 20kV and your transformer will 
not tolerate beyond 21kV, you then have only 1kV margin or less with the 
safety gap. But say main gap breakdown is 15kV, your safety gap margin 
and adjustment has increased. The problem is knowing the transformers 
actual death voltage or even the breakdown voltage of the gaps. So in 
the end, open it up as little as needed. It's a judgment call.

Take care,
Bart


David Nelson wrote:
> Bart,
>
> Thanks for your interest. I have removed half a turn from the inside 
> of the primary and moved the earth point on the strike rail to a 
> position further away from the secondary. I am now no longer having 
> problems with primrary sparking. The sporadic sparks at the end is 
> partly me having fun with my three year old (shouting in the 
> background) and partly because the safety gap was cutting in. I am 
> currently working on getting longer continuous runs. Some small issues 
> with the safety gap. I have reduced the number of gaps used in my RQSG 
> fromk 9 to 8 x 0.8mm with better results but I think the geometry of 
> the safety gap is letting me down - the center electrode is not 
> spherical, rather a flat brass bar with square edges. I will modify 
> this soon.
>
> It seems that when I set the safety gap without load, I need to open 
> it up much more (another 2 or 3mm) when the primary/secondary are 
> connected. Does this seem correct to you?
>
> Dave Nelson