On 8/10/17 9:08 PM, Steve White wrote:
It is tough getting a "good" earth ground (connection wise) and soil (even if you are operating in the proverbial salt marsh) is more resistive than chicken wire.If the earth ground is good, doesn't the earth itself below the topload act as the capacitor's other plate?
Remember that the return circuit carries the RF current (which isn't huge but is significant) but also the current from sparks (which is quite high, while the topload is discharging). I^2R losses add up fast when I is high.
----- Original Message ----- From: "jimlux" <jimlux@xxxxxxxxxxxxx> To: tesla@xxxxxxxxxx Sent: Thursday, August 10, 2017 11:02:28 PM Subject: Re: [TCML] First coil On 8/10/17 9:33 AM, Steve White wrote:I just completed my first tesla coil. It is a large one. Here are the prime specs. * 8.6" secondary with 1410 turns * 8 x 10 toroid * Center line of toroid is 71" above ground plane as defined by javatc * 12-turn primary currently tapped at turn 10.5 ( all primary circuit "wiring" is done with 3/8" copper tubing) * 45 nf of capacitance using 6 Maxwell energy discharge capacitors in a series-parallel configuration with load balancing resistors * 10 kva pole pig running at 14,400 volts * Sophisticated control cabinet including 25-amp variac, ballast, RSG phase control, breakers, contactor, PFC capacitors (currently about 150 uf), volt meters, current meters, EMI filters, MOVs, lockout switches, indicator lamps * Hand-made ballast with adjustable air gap currently set for 20 amps (similar to Richie Burnett's) * Rotary spark gap with one stationary 5/16" tunsten electrode and 4 flying 1/8" tungsten electrodes turning at 3600 RPM * HV leads made from 10,000 volt AC Belden test lead wire threaded through PVC tubing for additional insulation. This is all surrounded by grounded copper braid for uniform field distribution and to protect against streamer strikes. I made extensive use of javatc to design this coil. I was confident in starting with a large coil because I am a retired electrical engineer thus I had a lot of knowledge about electrical theory. I also own my own mill, lathe, bandsaw, oscilloscope, and signal generator. Finally, I had the funds to muy and/or build quality parts. Even though this was my first coil, surprisingly it worked the first time that I fired it up. I am currently getting 6.5 foot power arcs. It should be getting up to about 8 feet according to javatc. I am continuing to adjust the primary tuning. I think I need to go a little lower in frequency to account for streamer capacitance. I do have a few questions concerning RF grounding. I currently have a copper-clad steel rod driven 3 feet into the ground for the RF ground. This is as deep as I could drive it. I may try a water boring rod to try and get deeper. I currently have the following connected to the RF ground.It's not a "earth ground" that you need - you need a big counterpoise to serve as "the other plate" of the capacitor formed by the topload, and to complete the RF circuit in the secondary. Strips of chicken wire or hardware cloth would probably work fairly well. I'd start with a radius equal to the height of the topload above the counterpoise.* Strike rail * RSG motor chassis * Copper braid shield around HV leads * Copper braid around RSG power cord * Pole pig case Does this sound about right? Steve White _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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