High Voltage Forum

Tesla coils => Spark Gap Tesla Coils (SGTC) => Topic started by: Patric on August 25, 2018, 12:08:07 PM

Title: Difference between closed surface toroid and ringed toroid?
Post by: Patric on August 25, 2018, 12:08:07 PM
Dear all,
Most tesla coil designs feature a closed surface toroid top load whereas only the very large ones use toroids build from tubing rings. Can someone explain how a ringed top load compares to a closed surface one in terms of capacitance and overall performance? On a ringed torus what are the minimum gaps between the rings?
Thanks, Patric

Title: Re: Difference between closed surface toroid and ringed toroid?
Post by: Mads Barnkob on August 25, 2018, 03:37:33 PM
Hi Patric and welcome to HVF

I made two calculations in JavaTC, one for a solid toroid and one for a 7 ringed skeleton toroid and there is less than 10% difference in capacitance, you can see them here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/topload/

The skeleton toroid is a trade-off, it can not reach the same charge voltages that a super smooth solid toroid would, but a skeleton toroid only costs a fraction to produce.

Performance wise in a Tesla coil where we want to create lightning, there is not much difference. We need to shape a decent field to just keep the arcs away from the secondary and primary coils and we are happy :)
A solid toroid is however highly needed when you want to suppress outbreak, which electrons find very hard to do from the very even surface of a solid toroid, this could be in large HVDC installations for power transmission or those famous marx generator installations found overgrown in Russia.
Title: Re: Difference between closed surface toroid and ringed toroid?
Post by: Patric on August 26, 2018, 08:21:27 AM
Thx Mads, that's very interesting and opens up some more unusual design ideas that I have for skeleton toroid (love that word). I will share some CAD renderings once I am there.
Cheers Patric
Title: Re: Difference between closed surface toroid and ringed toroid?
Post by: Mads Barnkob on August 26, 2018, 10:32:19 PM
There are some good and ingenious ways of doing ringed/tube/skeleton toroids. I did the boring/normal 7 rings horizontal, but check these out.

From Zrg: http://4hv.org/print.php?plugin:forum.165062
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From a instruable with all calculations needed: https://www.instructables.com/id/Tesla-Coil-Wound-Aluminum-Toroid/
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Title: Re: Difference between closed surface toroid and ringed toroid?
Post by: Uspring on August 27, 2018, 12:14:32 PM
I once used a skeleton toroid with 8mm tubes. It had the tendency to break out from the bottom even though I had used a breakout rod. That lead to arcs ending on the primary. The larger effort to bend fatter tubes is well spent.

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