help with correct grounding

[lokeycmos]

if you look at pic, i have drawn up a few schematics of my proposed SGTC circuit. i have gathered these schematics from various websites and i need help with which grounding method is correct/best. i plan on using some RF chokes to protect the transformer. im a little confused because different websites show different grounding methods. please review my schematics and post some feedback on which to use or any changes i need. also, where does the strike ring get grounded to? thank you in advance!

 

[duffy]

Strike ring goes on the same ground as the secondary, so the "Earth Ground" in those drawings. That bottom one should have the safety ground on the mains ground.

 

[lokeycmos]

is it advantagous to use circuit 3 with the middle saftey gap connected to midpoint as to just circuit 2

 

[duffy]

It can save your transformer. Neon sign transformers usually have a separate bobbin for the HV winding placed well away from the primary, and they are usually potted, which makes them pretty tough to break from flashover. But given sufficient potential, an HV spike will bust through anything. I've had it crawl around the edge of a sheet of glass, I've sent it straight through 1/4" acrylic. Even with a safety rail there is a possibility the HV will get to something important.

The idea with that mysteriously-placed middle electrode is that the gaps have a lower dielectric strength than the internals of the transformer. Another way to do it is with a "Terry filter" made from a bunch of MOV's strung together.