Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx> Yes, my main gap is 6 X (5/8") Cu tubes, in series, each 2" long
From: "Tesla list" <tesla@xxxxxxxxxx> To: tesla@xxxxxxxxxx Subject: Re: Official air breakdown voltage? Date: Sat, 26 Nov 2005 17:01:39 -0700 Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx> At 12:56 PM 11/26/2005, Tesla list wrote:Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx>Maybe this is why my my capacitor gap fires at 18KV, when my system is run at 8KV (My capacitor gap is make of two very pointy objects, .75 inch apart, and it fires very loudly and frequently.)So basically, i need to use polished, smooth spheres for my safety gaps?Safety caps shouldn't be firing all the time, so the shape isn't super important (but read on), because you can just adjust it to where it fires at the right point (i.e. just not firing with the NST at max drive with no TC hooked up). However, sharp pointy electrodes tend to have erratic breakdown voltages that are more subject to outside influences. A loop of AWG10 solid copper wire is stiff enough to hold its shape and relative spacing. Something like carrige bolt heads would work well as a safety gap (although they wouldn't be all that suitable for your "main gap" for a variety of reasons). Brass drawer pulls make very nice rounded smooth electrodes, and they're cheap.Your main gap needs to be something that can take the heat dissipation.The classic "two bolts" type gap has real problems with getting the electrodes really, really hot, which then reduces the breakdown voltage (because the hot spot emits electrons) and erodes quickly. A nice, cheap, static gap is a few pieces of 3/4" copper tubing spaced evenly. It's got nice radius of curvature, it's got good thermal conductivity, and lots of surface area for cooling.From: "Tesla list" <tesla@xxxxxxxxxx> To: tesla@xxxxxxxxxx Subject: Re: Official air breakdown voltage? Date: Fri, 25 Nov 2005 19:55:16 -0700 Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx> Tesla list wrote:Original poster: "JT Bowles" <jasotb@xxxxxxxxxxx> I have read all over the net, around 25KV/inch <<I use this one I read on one place, around 30KV/inchNow i have just been told around 30KV / cm !!!! Thats 3 times the voltage I have been told It is common sense that air pressure, humididty, current, and time of day all affect air breakdown voltage, but: IS there any official way to determine exactly what air breakdown voltage is? ( such as KV/distance )30 kV/cm at normal temperatures and pressures, but this the ELECTRIC FIELD intensity that causes ionization in the air, and does not mean that is 30 kV for each cm in a spark. The value is directly proportional to the pressure of the air and inversely proportional to the absolute temperature. For two large parallel plates with rounded edges, the electric field between them is very uniform, and there are really 30 kV for each cm of spark. For an insulated ball far from other objects, the figure means that a ball with 1 cm of radius (and a well polished surface) requires 30 kV of potential (relative to distant objects) to ionize the air around it. Two balls with 1 cm of radius cannot hold a voltage of more than 60 kV between them without corona or sparks, no matter what is the distance between them (less if they are close). Antonio Carlos M. de Queiroz