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*To*: tesla@xxxxxxxxxx*Subject*: Racing Arcs Explained???*From*: "Tesla list" <tesla@xxxxxxxxxx>*Date*: Mon, 14 Aug 2006 20:04:40 -0600*Cc*: dest <dest@xxxxxxxxxxx>*Delivered-to*: testla@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*Old-return-path*: <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>*Resent-date*: Mon, 14 Aug 2006 20:04:39 -0600 (MDT)*Resent-from*: tesla@xxxxxxxxxx*Resent-message-id*: <rDfnMzjODYK.A.saF.3uS4EB@chip1>*Resent-sender*: tesla-request@xxxxxxxxxx

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx> Hi,

Cheers, Terry

Hi, Just to follow up... If we take the example Dest gave: http://www.pupman.com/listarchives/2006/May/msg00381.htmland convert it to "inches stuff" with just minor length changes toget round numbers we get:PrimarySolenoid - 6 inches high, 12 turns, 11 inches in diameter of 3/8inch copper tube.Secondary - 28 inches long, 1500 turns, 7 inches diameter. 0.015 wire. Firing voltage 20kV.But he does not mention Cprimary... That value is needed to knowdi/dt which is critical factor too...So we add a 6 x 24 toroid top terminal with a centerline six inchesabove the top of the secondary. We can now go to JAVATC to find Fo and such...http://drsstc.com/~sisg/files/RaceArc-01.gif 91.67kHz and the primary is 39.462uH with a coupling of 0.306...We will assume now that the primary is tuned 5% low as usual andfind Cprimary as 85nF. A coil this size with 0.3+ coupling and 17joules per bang "should" be a racing arc disaster!!!Totally ignoring any "resonant" effects and totally relying on "puretransformer action", the voltage induced in the secondary is:V2 = M x di(Lp)/dtSince M varies drastically along the length of the coil, we have tochop it up and calculate it in little chunks or sections... We'lldo every 0.1 inch since the computer is doing all the work ;-)) SoI pump it into MandK and get this:http://drsstc.com/~sisg/files/RACEARC4.TXT So we know the mutual inductance of each little section now... To find di/dt we know Ip is in the first instant of firing: I(t) = Vfire x SQRT(Cp / Lp) x SIN (t / SQRT(Cp x Lp)) If we take the derivative:dI(t)/dt = Vfire x SQRT(Cp / Lp) x 1 / SQRT(Cp x Lp) x COS(t /SQRT( Cp x LP))If t ~~= 0 and with some simplification we get: dI(t)/dt = Vfire / Lp == 20000 / 39.462uH == 507e6 A/S Now we can get out the spreadsheet and make some numbers: http://drsstc.com/~sisg/files/RaceArc6.csv and we can make pretty graphs: http://drsstc.com/~sisg/files/Voltage-length.gif http://drsstc.com/~sisg/files/VoltageEveryInch.gifSo at 3 inches, the voltage stress along the primary is 35000 volts/ inch in the first fraction of a microsecond after firing.... Destgot 40kV/inch too!!! We can look at this chart:http://hot-streamer.com/TeslaCoils/Misc/SGapVolt.jpgTo see that it will jump 1.26 inches!!! We have an arc for sure,and super sure too since it is a surface creepage arc that willactually arc at even far lower voltage...Worse yet, once the arc is established, it will look much like ashort on the secondary and will very quickly absorb all the energyin the bang. Thus explaining why they are "bright" arcs that do alot of damage...On the good side, thick layers of insulation should protect againstsuch voltage breakdown!! Put that poly coating in real thick ;-))Of course, once the resonance is established, such effects will"ride" on top of the voltage on the secondary too... I imagine thatwill explain the arcs occurring at places other than the base of thesecondary...The voltage profiles Paul has at: http://www.abelian.demon.co.uk/tssp/pn040502/ Will enter into this all too... Of course, Gerry's paper provided the key to it all ;-))) http://hot-streamer.com/temp/GerryReynolds/In_search_of_a_better_primary.pdf I CC'ed dest too incase he has comments... Cheers, TerryHi, Dest also looked into this: http://www.pupman.com/listarchives/2006/May/msg00387.htmlBut I don't think he did it quite right... The links are dead so Ican't check now. ...........

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