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surface breakdown was Re: 20 joules at 100 bps vs 4 joules at 500 bps



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 07:25 AM 8/3/2005, you wrote:
Original poster: Greg Leyh <lod@xxxxxxxxxxx>

You're correct -- a toroidal electrode would have provided far better field control than the spherical electrode used on Electrum. The spherical electrode geometry was part of the overall aesthetic requirement however, and had to be accommodated. As a result, the operating instructions for the machine specify to immediately remove power for 5 seconds if a tower strike is observed.

Based on experience, 5kV/inch seems to be a reasonable surface gradient to maintain on the outside of a secondary form.

Is that for creeping discharges on the surface, or a "free air" distance from toroid to base? Seems a bit low for the latter.



The next secondary coil that I'm working on will have convolutes on the outer casing, like this: http://www.lod.org/Status/90L10KPhotos.htm The intention here is to support higher surface fields than a standard external winding, without requiring significant amounts of transport care or maintenence.

What sort of manufacturing process would you use for this? Cast the corrugations after winding? I assume you're not actually winding on the inner surface of the corrugations.


What about making a regular tubular secondary, then bonding disks with a hole in the middle along the tube. You'd want a real good bond with no pinholes. The advantage might be that you could use different materials for the two components.

Or, on a very larger scale, what about building the secondary as a stack of modules that get bolted together(like they do for HV string insulators or for high power EHV converters).