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Re: [TCML] Greetings from new coiler in Australia



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
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