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

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Paul Benham" <paulb@xxxxxxxxxxxxxxxxxxxx>

Hi All,

If higher coupling is the way forward why not go to a much larger secondary
diameter.  Then for a given spacing the coupling will be higher.  Kind of
like a magnifier except there is no capacitance or transmission line on top
of the wider secondary coil.

You could build a DRSSTC like the coil Bart built with the secondary on top
of a bucket or something with the first few turns on a much larger diameter.

If there is flashover then only increasing the air gap distance will fix
this.

Cheers,

Paul.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, December 16, 2005 7:50 PM
Subject: Re: A LUA file for BELA (a help to build electrostatic model of TC)


> Original poster: Finn Hammer <f-h@xxxx>
>
> <Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>wrote:
>
>
> <snip
>
> <You don't really need to do heavy electrostatic analysis or
> differential equations to <get it right the first time!!
>
> <snip
>
> DC,
>
> Your approach to Tesla Coil Design is fine for conventional disruptive
coils.
> I have been here 8 years now, and have gained enough experience to
> acnowledge that.
> However, the electrostatic analysis i am playing with, is aimed at
> the new breed of coils.
>
> The DRSSTC`s.
>
> Those of us that have built this type of coil can witness to the
> fact, that flashovers from secondary to primary still is a limiting
> factor with these coils.
>
> In an attempt to solve this problem, I have tried to add increasing
> amounts of dielectric in the space btwn. the 2 coils, only to observe
> that the problem got worse.
>
> 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.
>
> The air has to be excluded all together to avoid corona in such strong
fields.
>
> I like to put the primary coil inside the secondary, but the problem
> also exsists in coils that have visible primary`s.
>
> Pls. review this design example to understand my point of view.
>
> I have a 200mm secondary with a voltage profile of  600kV/metre.
> I want the primary coil to be inside the secondary, and I want full
> access to that coil for tapping purposes.
> I already know that there is a corona problem that ruins the
> secondary coil from inside, without actually puncturing the coilform.
>
> In the following pictures, the colour legend is set to display a
> field strength of, and beyond 3MV/m in the magenta area.
> Corona will form in the red magenta area.
> Of course it will happen at the top turn.
> http://home5.inet.tele.dk/f-hammer/DRSSTC1.jpeg
> First thing would be to introduce a grounded and slotted (slotted how
> and where remains to be determined) shield.
> http://home5.inet.tele.dk/f-hammer/DRSSTC2.jpeg
> Obviously, this was too simple a shield, I`l add a rounded top detail.
> http://home5.inet.tele.dk/f-hammer/DRSSTC3.jpeg
> That doesn`t really cut it either so I`l have to close the shield off
> at the top. Notice how it starts to resemble a cheap and readily
> available cooking utensile.
> http://home5.inet.tele.dk/f-hammer/DRSSTC4.jpeg
> So far so good. Now the primary is safe and sound inside it`s
> grounded shield, no need to worry about the primary getting hit by
> flashovers. But the corona problem still exists btwn. shield and
> secondary, due to the insulating substance being air. (which in it`s
> highly electrically stressed state has quit being an insulator and
> become conductive).
> This is where the potting compound comes into the picture. With a
> voltage standoff ability of 50MV/m it is safe and sound in there, I`l
> just pour it in. (Yeah I know, no air bubbles, no voids, vacuum)
> http://home5.inet.tele.dk/f-hammer/DRSSTC5.jpeg
> But whoa! hold your horses! A new area of potentially ionized air has
> appeared outside the dielectric. Guess I have to pour some more
> potting in there:
> http://home5.inet.tele.dk/f-hammer/DRSSTC6.jpeg
> Ok, now it is time to stop simulating and go to the shop.
>
> With this example I want to show a couple of things.
> At first encounter, the interface of air to dielectric is counter
intuitive.
> At 400USD/Gallon of potting compound, it pays to be at least
> rudimentarily prepaired, before pouring.
> Doing an electrostatic analysis of this problem paves the road to a
> successfull design.
>
>
> There is another thing. I am a tool maker and a podiatrist. Many
> times I wish I was an EE, but I`m not. I would so much like to join
> the discussion based on knowledge.
> So I study. Seek out tasks that need both manual skill and
> theoretical knowledge to complete with success.
> For a period, it has been my ambition to build a tightly coupled
> resonator pair with an internal primary, so far this analysis seems
> to have brought me closest ot the fulfilment of that goal.
>
> Cheers, Finn Hammer
>
>
>