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Re: A LUA file for BELA (a help to build electrostatic model of TC)



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


Mainly, to overcome the poor field control of just the smaller dia. copper tubing. In most systems the subbase is elevated a distance above the surrounding groundplane (it should be or much of the energy from the pri is stolen by the groundplane) so the field control could be better at the lower end of the coil --- the groundplane isn't quite as close if the subbase is elevated.

In some of our systems the pri sets as high as 40 inches above the surrounding groundplane.

All I'm suggesting is some comparative experiments in this area.

Maybe your electrostatic program could actually do this without conducting an actual experiment if it allows for primaries elevated above the groundplane.

Dr. Resonance




Original poster: Finn Hammer <f-h@xxxx>

DC,

Toroids are great and classic devices in the quest for a more uniform field.

A tertiary magnifier coil is a good example, where the potentials of both ends of the resonater are above ground level, and the field strength is aligned in the coils axial direction. A toroid in both ends of this coil is mandatory, to avoid corona loss. This applies particularly to the bottom end. In the other end we do of course not only accepy, but ultimately rather desire corona loss. In the example you put forth, where discontinuities exist on a conductor at high potential, a toroid is also advisable at each discontinuity.

I do however fail to grasp, what a toroid at the bottom of the coil in question would acheive in the line of field controll, since both coils at the bottom are terminated at ground potential. The field strength in this example is aligned in the radial direction of the space btwn. both coils.

How do you expect to smooth a _radial_ field with toroids?

Cheers, Finn Hammer

Tesla list wrote:

Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



One impovement to this design would be using a toroid on the bottom of the coil as well as on the top. Just using one on top shapes the field but the smaller dia copper tubing in the base area does not provide effective electrostatic field control in this area. Using a toroid on the bottom as well as on the top will help provide better control of the fields and reduces the insulation required. As you noted just using more insulation does not give good uniform field control. You need to shape the fields with proper electrostatic shielding techniques.

These principles are used in very high potential 60 Hz xmfrs used for research work. A nice toroid is placed in the case entry area and many times actually inside the case near both the bushing tip and also near the area when the bushing departs the case.

Dr. Resonance






Original poster: Ed Phillips <evp@xxxxxxxxxxx>


People who work with tightly coupled transformers for high voltage know it already, but I have only recently found out: I cannot insulate my way out of a corona problem. The more dielectric I stuff into the gap, the more severe the corona gets in the remaining air.

Ain't that the truth..."

Of course; "it has to be that way". The more (higher dielectric constant than air) material you put in the gap the greater the voltage drop across the remaining air and hence more corona. IF you completely fill the gap and IF you exclude all residual air the corona will be suppressed. If a little air remains somewhere it will break down due to corona and may very well result in breakdown of the associated dielectric material. Major failure mechanism for capacitors operated at high AC voltages.

Ed