BrOdin coil - High power Big sparks!

[davekni]

Just a guess, but I suspect more concentric ground rings and/or larger tubing diameter for the one ground ring would help.  My DRSSTC initially had trouble arcing from ~1/3rd of the way up secondary to ground ring.  Appeared that the arcs actually started from ground ring asperities.  Ground ring tube diameter is much smaller than secondary diameter.  This can result in higher field strength adjacent ground than adjacent secondary coil.  Were your ground ring arcs at the ground ring gap?  Likely highest field there.  (My updated DRSSTC has three concentric ground rings that are each almost complete, with just a couple mm of insulated gap.  Outside the largest one and slightly below is a grounded wall made of foil-covered foam-core board.)

Wow, frustration in the extreme!  (I'll experience that if my H-bridge ever blows.  40 individual TO247 IGBTs will be difficult and tedious to replace.)  Take a break for a while until you are motivated to try again.

Good luck!  First, relax and do something different for a bit.

[alexhanyuan]

Freddie, any update on this? Wind a new secondary yet?

Looking at that frame grab of it arcing, it looks like it originated from the end of the strike ring. I bought copper end caps and simply slid them over the ends of my strike ring to round it out. Though it seems you've cut them flush with some primary supports and this isn't as easy. Phil has soldered on brass balls to the ends. You could also just slide the ring a bit and not pass it through one of your supports to get access to the ends.

Maju has a good point as well, get an oversize acrylic/plexiglass primary cover that extends well past the strike ring. Of course, your strike ring no longer serves a 'strike ring', only field control on the edge of your primary coil. Most important thing... absolutely no holes in this disk!! Any holes for mounting can potentially allow an arc to pass through it.

BTW, Maju, your screen grab is of Florian's coil, not Phils. Same exact concept though.

What is your procedure for coating the secondaries? Between me and Phil, we have had some pretty nasty flashovers that we were sure killed our secondaries. After wiping off all the soot it was fine though. Thick epoxy layers is the way to go.

[fh89]

Haven't had the resolve come back quite yet, been spending time and money on other hobbies- bought a '22 BMW S1000RR and have been wrenching on that with tons of mods.


But I keep seeing that burned up secondary sitting in my garage and the need to build it back better than ever is building.

Yeah, the flashover was definitely from the strike rail. I have new copper tubing I can use for a new one with some type of rounded ends.

The polycarbonate disc I had covering the primary coil was totally destroyed in this incident and requires replacement, but I think the rounded strike ring ends you mentioned will solve the issue and I can keep my strike ring functional.

This secondary had 3 coats of Famowood Glaze Coat epoxy, by far the best finish I had on a secondary coil so far as I am getting pretty good at it after destroying so many! I've had those smaller flashovers as well where I just wiped off some black carbon and all was good, but this one instantly vaporized 15-20 turns or so, just instant total destruction this time.