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Re: flashover
Original Poster: "A W" <fateagk-at-home-dot-com>
I am still trying to get my first coil together. I have been plagued
with flashover arcs from my primary to the secondary. I am using a
7.5kv/30ma NST, saltwater bottle caps with total of .013uf, a single
static gap(2 brass bolts), and a 4" PVC secondary wound 21" with #24
magnet wire. I originally had a 14 turn primary of 1/4" refrigeration
tubing in a flat spiral. It had 1/4" spacings and had an inner turn
diameter of 7". It arced so bad that it seemed to turn the distance
between the primary and secondary into a 1.5" gap. I put a section of 6"
PVC between them, changed the coupling, wrapped both in electrical tape,
covered the first turns of the primary in clear tubing, tried different
tapping points on the primary, all to no avail! I scrapped the 1/4"
refrigeration tubing primary and have made a new primary. I made a 11.5"
diameter helix spiral primary using 12ga wire. Remember, my secondary is
4" diameter PVC. It is now arcing over 3" to get to the secondary. I
cannot make it stop. I am using the same 7.5/30 NST. I have checked the
entire circuit and cannot find anything that looks fundamentally wrong,
so why is this happening. I have tried it both with the RF ground on the
secondary, and without. I have wrapped the bottom half of the secondary
in electrical tape, and placed a section of 6" diameter PVC around the
primary. It has now burned the PVC, smoke was everywhere! I have been
checking tons of websites on the internet and I have yet to see an
instance where the primary requires more than three times the diameter
of the secondary. Could it be my transformer? I am getting to frustrated
with this! HELP!
Thanks,
Andrew
I had this happen with my first coil. I was using a cylindrical-wound
primary a few big arcs kept flying from the top windings of the
secondary to the primary. I stopped this by using the extremely
scientific method of going to a car accessory shop and buying a
large rubber car-floor mat. I wrapped it tightly around the secondary,
going right up to the toroid (actually it was a copper sphere), and
secured it together with around a dozen plastic loom ties. This stopped
all arcing and I didn't need to adjust anything in the setup.
Richard.