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Registered Member #2263
Joined: Mon Aug 03 2009, 04:57PM
Location:
Posts: 20
I have been searching the net for info on hv construction, I cant find anything about grading rings, can someone please explain what they are and why they are necessary?
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
They reduce the potential differences thereby reducing the amount of corona. They are ring shaped to prevent them from also making corona as they are floating at a certain potential. The rings make the entire stack seem more like a single large insulator with an even field distribution instead of two short sections of wires with sharp points. A final toroid on the top will also help even out the field. The tiny balls you put on the leads of the caps and diodes do help but not enough to stop the corona. The corona could also be coming from the leads between the the diode strings and the cap leads.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Check out Glassman's CW stacks to see what we mean by grading rings, toroids and so on. The black rings and the small silver toroid halfway up are the grading rings, they're connected to the intermediate CW stages.
Registered Member #2263
Joined: Mon Aug 03 2009, 04:57PM
Location:
Posts: 20
I attach a photo of perhaps what you guys are talking about in terms of field rings, I have to say though I had to go through hundreds of images of high voltage generators to find this. They only seem to be used in huge accelerators producing Mega volts. I couldn't find a single home build CW unit with field rings around it. Just wondering why nobody else has bothered to use them.
Are these rings wired into the CW or just free insulated conductors which will pick up a charge?
Registered Member #2123
Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312
That's a bit big for what he is doing. Heres a picture of a 180KV CW from an Ion Implanter showing how the field rings are placed (I have three of these).
Registered Member #2263
Joined: Mon Aug 03 2009, 04:57PM
Location:
Posts: 20
I could easily improvise a few conductive rings around my CW tower, are the rings connected to anything or just supported by insulator supports and isolated form each other and the CW tower components?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I believe they're connected up to the CW's output capacitor stack. So for instance if a ring was halfway up the tower, it would have half of the output voltage on it.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Sparks wrote ...
We talking something like this? It seems to me that this ring configuration could cause arcing to ground if too many are used?
from what I understand, the rings cannot have a potential that is more than your input voltage, for the same reason no individual capacitor can have more than the input voltage - so as long as the rings are not terribly close to a ground source you should be fine
I have never used rings, but if I ever make a large design I intend to
Crongrats on such a good design with room to improve!
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200KV PLUS voltage multiplier
