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Old 26th Nov 2017, 12:34 pm   #10
Al (astral highway)
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Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
Default Re: Cutting (router) a circular flashover guard for me?

GJ:

Thank you for your insightful comments. You have raised the distinction between surface tracking and other unwanted arcing. On reflection , I think that surface tracking is more the culprit. At EHT HF RF and apparently well over the design voltage in an transient fault condition, the pulses in the primary coil are extremely energetic and arcs can pop up between coupled inductors with savage destructive force. They can easily punch holes in insulators very widely spaced apart if the surface provides a temporary conductive pathway. I wish I had high-speed camera triggering to record the exact mechanism.

The best approach is for me to avoid a fault condition, caused by poor tuning. The support to this is to consider the surfaces that are becoming a conductive pathway. Building up a ridge of non-conductors across this pathway seems a good idea and so does your idea of adding a retardant reagent such as the one you have linked to.

Argus25: Thank you : really good suggestions there on the materials side of things. The mica looks like a great candidate for insulating the tank circuit from adjacent conductors.

Mark: also thank you! I’ll PM you as some offcuts of polycarbonate would be useful!!
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