Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>JT, you're not listening. I said you can ONLY use 30KV/cm and a meter stick to calculate breakdown if it is a UNIFORM FIELD. This is rarely the case unless you have two parallel plates where the plate separation is small compared to the size of the plate. The 30KV/cm is a field strength the the air molicule experiences. This field strength may be present only in a very localized volume.
Gerry R.
Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx> You said:"The breakdown for air is approximately 30KV per cm. This is a local field strength and if the field is uniform (constant) then you can measure the distance to find the total breakdown. The 25KV per inch you found probably assumes a geometry and applies to a short range of distances. "Well holy crap, that throws ALL my measurements with high voltage off a lot. My sparkgap for example is set at 7.5 to 8 mm. That means my sparkgap is set at 22.5kV? NO WAY; MY TRANSFORMER OUTPUTS 12KV ONLY. SO, IF IT WERE SET AT 22.5 KV, IT WOULDNT FIRE WORTH CRAP.THIS MEANS THE FORMULA: 1cm=30KV cannot be correct Thanks a ton for the help, but I THINK you're wrong buddyFrom: "Tesla list" <tesla@xxxxxxxxxx> To: tesla@xxxxxxxxxx Subject: Re: Safety gap issues Date: Fri, 25 Nov 2005 08:00:02 -0700 Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi JT,Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>Use a counterpoise? You mean putting large amounts of al foil, spread on the ground, as an RF ground? WTF no way dude, that ruins the aesthetics of my coil.Counterpoise was for indoor operation. If you are outdoors and have a rod in the ground, GREAT. Keep the NST with the coil and ground the NST, secondary base, and strike rail to a common point and run a heavy short wire between this common point and the pipe in the ground (RF ground). Your target for sparks should be grounded to RF ground at the common point (not the pipe end). This keeps strike return current out of the heavy wire to the pipe and will help keep RF ground noise to a minimum. Ground your variac and line filter to mains ground.The breakdown for air is approximately 30KV per cm. This is a local field strength and if the field is uniform (constant) then you can measure the distance to find the total breakdown. The 25KV per inch you found probably assumes a geometry and applies to a short range of distances.Gerry R.i DO have a 4 foot Cu pipe driven into the ground, and 15 feet of wire is attatched to it. *I use this separate ground as a ground for the sparks to jump to.(from toroid directly to this)*I have read all over, 1 inch requires around 25,000 volts to make a spark connect. So, i have been measuring EVERYTHING using this equation. IN OTHERWORDS, I USE 1MM=1000V. My sparkgap is set at 7.5 to 8 mm, thus 7.5 to 8 kV* my output is 15.5 inches- so i times that by 25,000 volts per inch- to achieve a staggering388KV tesla coil output I HOPE YOU GUYS CAN UNDERSTAND EVERYTHING I JUST TYPED!From: "Tesla list" <tesla@xxxxxxxxxx> To: tesla@xxxxxxxxxx Subject: Re: Safety gap issues Date: Thu, 24 Nov 2005 10:38:19 -0700 Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx> Hi JT,An unloaded NST is with no load attached to its output. 12KV is an rms voltage which means that peak voltage is 17KV (Vpeak = 1.414*Vrms). A two bushing NSTs would have 6KVrms (wrt ground) on each bushing (12KVrms between the two bushings) . Don't know how you are measuring your voltage, but a ruler isn't the way to go. Set each side of your safety gap with no load attached to the NST. Then you can reconnect the TC primary.If you use the mains ground for an RF ground, do not allow the coil arcs to hit anything (walls, ceiling, etc) not directly grounded to the TC secondary base. Use an outlet on a circuit breaker branch that is not shared with anything else and use a counterpoise. Also unplug anything electronic (TV's, computers, etc)Best to go outdoors and ground your TC secondary base and strike rail (if you have one) to RF ground (rod driven into the earth with wet soil). If the NST is located with your TC (like just under the TC primary), I would ground it (along with its protection circuit) to RF ground and NOT to mains ground. If you use a line filter, it should be grounded to mains ground. Your variac should also be grounded to mains ground.Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx> TWO THINGS:1.) I know this is "very, very bad" but i use mains ground for my entire circuit 2.) that being said, i have my NST, safety gap, and secondary all linked to the same exact ground*what do you mean unloaded NST? You want me to basically disconnect the ENTIRE tesla circuit, after my safetygap? If i do so, the safety gap will fire, up to aobut 15KV.15KV is still enough to damage my transformer's(12,000/30 ma) secondary isnt it? So, my safety gap would be useless set at such a huge voltage. I think it should be set at about 1KV over what my NST is set at. (my NST is set at 7,500 volts with my spark gap, so the safety gap should be 8,500 to 9000 volts)NO ONE HAS ANSWERED MY QUESTION YET THOUGH: CAN MY EARTHED MIDDLE NODE ON MY SAFETY GAP BY REPELLING A SAFETY SPARK?Not sure what your question means. Gerry R.