Tedd, A very good question!Energy absorbed by a shorted strike rail is energy that would otherwise be available to excite the secondary and create longer sparks. The total system energy each time the gap fires is fixed by the bang size (0.5 CV^2). So, any additional system losses will reduce the maximum energy that can be transferred into the secondary, resulting in shorter sparks.
The radiation example you provided is a bit more complex. In a TC, energy is transferred between primary and secondary via classical electromagnetic induction, or "transformer action". Electromagnetic energy between primary and secondary said to be coupled through the "near-field". In this region, any changes in secondary loading will have a direct impact on primary loading, similar to any other transformer. The region near the top of the TC is dominated by E-field (capacitive) reactance. In the reactive zone, energy absorbed by any near-field element will directly reduce the energy available to all other near-field elements. In the near-field, reactive magnetic (H) and electric (E) fields are 90 degrees out of phase. Reactive energy in the system cycles between the electric (E) and magnetic (H) fields on every 1/4 cycle.
Once you go out several wavelengths away from a radiating system, you are in the far-field region. In this region, EM radiation behaves in a more normal fashion. In the far-field, absorption of radiation does not feed back to the transmitter. Nor does it reduce energy to other receiving antennas. In the far-field, magnetic and electric fields are IN phase, and the ration of E/H approaches free space impedance of 377 ohms. Antennas are specifically designed to be efficient EM radiators.
Tesla Coils are very poor radiators. Most nearby non-sparking phenomena (such as wireless lighting of handheld gas tubes) are due to near-field capacitive (E-field) effects.
Bert Tedd Dillard wrote:
Gentlemen permit me a follpw up question. I understand that the heating of a closed loop rail is absorbing energy. But is the energy that which would other wise be going into the primary such that the power into the primary is being reduced? This may be a false example but a radio transmitter transmits the same energy regardless of how many receivers are operating. The energy received by one does not affect that of other receivers Teddy On Jul 8, 2018 12:00 PM, "phil" <pip@xxxxxxxxxxx> wrote:Teddy. Your question makes a good point, and the explanation is as Garry states; I was simply drawing attention to the fact that the coil's owner had remembered to place a gap in the ring. I'll add something in the description. PS: I'm not aware of situations where you would have a closed loop (maybe others are?) Phil T On 08/07/18 00:45, Tedd Dillard wrote:Gentlemen the reasons for my question are; 1. I am new at this so am trying to understand how these things work. They are obviously complicated so getting into details is important. 2. In reading past post I remember some discussion on strike rings that included some reference to open and closed loop rings but I was not clear on the issue. 3. In the video of the damage to the secondary one of the captions indicated an open loop strike ring so I wondered if there was any significance to specifying that it was open loop. If no one runs closed loop why say it was open? Teddy On Jul 6, 2018 5:22 PM, "Steve White" <steve.white1@xxxxxxxxx> wrote: If it is heating then it is absorbing energy. Heat takes energy togenerate. A closed loop that is grounded would be just as effective as an open loop that is grounded but why would you even want to consider that unless this is just casual interest? It is simple enough to cut a gap in the ring. Steve ----- Original Message ----- From: "Tedd Dillard" <tedd.dillard@xxxxxxxxx> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Friday, July 6, 2018 8:16:04 AM Subject: Re: [TCML] Fixing secondary strikes Re: Bad strike to a 12 inch traditional coil (somewhat terminal) Carl thank you for your quick response. In a closed loop does the energy going in to heating the loop detrack from the energy going into the primary or is the heating the only issue? Is there any effect on the effectiveness of the loop to protect the primary if it is an open loop. Teddy On Jul 5, 2018 10:15 PM, "Carl Noggle" <cn8@xxxxxxx> wrote: Hey-- A closed loop ring will act like a single shorted turn coupled to the primary. If it has a much bigger radius than the primary, it probably won't absorb too much power. But is it's close, it will absorb a lot of power just heating up the ring. Putting a small gap in the ring eliminates this problem. --- Carl On 7/5/2018 5:51 PM, Tedd Dillard wrote: Gentlemen this may not be best place to ask this question but I noticedinthe vedio that it was an open loop strike ring. Comments on thedifferencein an open loop vs closed loop strike ring please. Teddy On Jul 5, 2018 1:31 PM, "Bert Hickman" <bert@xxxxxxxxxxxxxxxxxxxxx>wrote:Phil, Steve, and all,Sorry for the damage to your secondary, Phil. The videos were excellent and will hopefully lead to good discussion here and effectivepreventativemeasures for higher power systems.A thick coating of 2-part epoxy or polyester may accomplish a similar function as PMMA tubing at significantly lower cost. When uniformly coated, errant strikes to the secondary will "splash" outward across arelativelywide area of the outer surface of the coated secondary. The coatingdissipates spark energy by spreading it out and capacitively conductingitto the secondary without creating damaging hot spots. In practice, I'veseen hot primary-secondary flashovers that left NO permanent or visible effect on thickly-coated secondaries. These would have undoubtedlycausedmelting and turn-turn shorts on an unprotected secondary.Your system also has a comparatively large topload OD compared toprimaryOD. You may want to consider adding one or two additional,larger-diameter, strike rails to spread out the E-field "footprint" of the base. Thesewillalter the E-field between the topload and base, making it more vertical(in the space between the two) helping to reduce strikes to the secondary.Thelarger strike rails could be an add-on that can be removed beforetransporting the coil, and they would would require any changes to your existing primary winding. You may also want to consider adding a smaller toroid under the top toroid. By elevating the top toroid, you'll increase the outward "throw" of sparks while further reducing hits to the strike rail. In the latestvideothere were a number of hits to the strike rail that came quite close toflashing over to the lower half of the secondary even at 100 BPS. The hotter 200 BPS strikes combined with thermal rise seems to have tippedthebalance, unfortunately.Good luck and best wishes, Bert Steve White wrote: I have also had this idea for some time. I would love for somebody totrythis but even if it works I don't know if any of us could stand theexpense. Steve ----- Original Message ----- From: "Phillip Strauss via Tesla" <tesla@xxxxxxxxxx> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx> Sent: Wednesday, July 4, 2018 4:02:13 PM Subject: Re: [TCML] Fixing secondary strikes Re: Bad strike to a 12inchtraditional coil (somewhat terminal)Hello Jim, Although very costly in the UK, I was considering a 350mm diam cast acrylic 1 metre long tube (that's how it comes) with 5mm wall thickness to go over my 300mm (12") diam secondary, it would cover about the firsttwothirds of the tube, a good few inches higher than the previous strikes.Your comment on a dissipative tube caught my eye for that particular reason but I don't understand the concept of loading or that my idea wouldwork,any explanation and/or prediction would be much appreciated.I'mcontemplating your other suggestions (which are totally novel <https://maps.google.com/?q=her+suggestions+(which+are+totally+novel&entry=gmail&source=g>to me) withinterest. Regards,Phillip. ____________________________________________________________ _________________ 14 Broad Street, Stamford, Lincs PE9 1PG Tel: 01780 753008 On Wednesday, 4 July 2018 21:26:39 BST, jimlux < jimlux@xxxxxxxxxxxxx> wrote: On 7/4/18 11:40 AM, David Rieben wrote: Hi Phil,My deepest condolences for your loss. I know it's JUST a secondarycoil,but as a fellow coiler, I most assuredly feel your pain. On the brightside, at least you did manage to capture some truly spectacularfootageof this secondary coil mishap. I have had this happen on rare occasionwith the operation of my big coil, though fortunately, none of my mishaps turned out quite that severe! Only once did I actually have to repair some damage to the side of my coil and was able to get it back into full functioning mode via the repair. Since I must operate mine outside, I did have one occasion where the wind actully "blew" one of the streamers back into the side of my secondary coil, too. Lesson learned - although refraining from outdoor operation during rainfallisan obvious good rule, non-starters in windy conditions are also welladvised. I suppose this is a risk, that although may be small with a well-tuned and efficiently operating coil, is never completely absent. :^/ I wonder if we could figure out a way to segment a large coilvertically, so if a segment gets damaged, you can just rewind that segment. Just off the top of my head, I'm thinking about something like segments with a hundred turns or so. Could we come up with a way of making the connections in a "good" way. I'm almost thinking about how you using field grading rings on a Van de Graaff. You don't want a complete shorted turn, but you could terminate the winding in some sort of flat terminal on the "mating face" of a segment. You'd stack the segments, and then put some compression on it (threaded fiberglassrod?)The other idea that comes to mind is if there is some way to "spread"the energy of the secondary strike.. Say your secondary were coatedwitha resistive (but still conductive) coating. Would that spread thecurrent density enough to prevent burning through the insulation? Or a dissipative tube covering the secondary - not enough to "load" the secondary, but enough to "take the hit". OR, what about a second helix, space wound, that extends the length of the secondary, with some suitable resistive conductor, so the voltage profile matches that of the secondary (so no protective helix to secondary arcs), but so it doesn't enter into the resonant circuit. The protective helix would be mostly capacitively coupled to the secondary, establishing the voltage. What about something like a helix wound with wire, but with small gaps along the length.. the gaps don't break down normally, but if astreamerstrikes, the gaps break down and provide a conductive (but lossy) pathto the base. _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla _______________________________________________Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla-- Regards Phil www.hvtesla.com _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxxxxxx https://www.pupman.com/mailman/listinfo/tesla
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