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

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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).