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*To*: tesla-at-pupman-dot-com*Subject*: Re: LTR Pig Project -biggg coil*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Sun, 18 Feb 2001 20:01:17 -0700*Resent-Date*: Sun, 18 Feb 2001 20:13:04 -0700*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <r0XkdD.A.yeE.x8Ik6-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz> Hi Kevin, On 18 Feb 01, at 14:13, Tesla list wrote: > Original poster: "Kevin R Eldredge by way of Terry Fritz > <twftesla-at-uswest-dot-net>" <kreld-at-juno-dot-com> > > > > All > > I just picked up on this post, and wanted to clarify several things > that might help out. LTR or not? I won't guess, it works, and I'm > happy. (:D The Biggg Coil project was a "everything new > from the start" project. That is, all components involved were not > used on any other of my Coils, except for a contactor and fine tune > inductive ballast. This made things a lot harder to find initial > problems, but thanks to John Freau for guiding me the right way on the > break rate. > The whole project evolved around the purchase of two 0.376 uF > cap's which are wired in series (0.188 uF approx). > > The only math involved was for basic resonance,ie..secondary, > primary, capacitor parameters. Problems were many. Initialy the > sync. Rotary was at 480 BPS. This pulled 300+ amps from the 245 volt > mains, and only 14' sparks. Ballast adjustment made no difference. > Removing gap electrodes for 240 BPS operation made things better, > current down, sparks longer, but still not right. > Finally running 120 BPS, current came down to 110 amps, at > 300 volts at the pig's, 24' sparks. This was new, 300 volts AFTER > the inductive ballast, 240 volts before the ballast. I unfortunately > did not measure the actual 245 volt current into the control cabinet, > this Spring I will. Your ballast is resonating with the primary cap. > As John stated, the external ballast gets real hot, smoking hot. > However, the ballast is a 15 kVA transformer with the secondary > shorted, so this creates most of the heat, the shorted winding. > This too will be addressed this Spring with a new ballast. > The internal switchable ballast, runs only warm, it's simply > #10 wire wound on a steel torroid. The smoke represents copper losses and core losses. Regards, malcolm > The coil has been dormant this winter, but as weather warms, > the coil will be brought out to play again. Simply getting things to > work was the goal last year, this Spring will bring a new 10 x 10 x > 16' building to keep the Coil in a ready to fire state. Also the > rotory will be rebuilt with on the fly phase adjustment to better tune > while adjusting reactive ballast for maximum spark. > An old tube scope is being modified to accept high voltages > directly to the CRT's deflection plates through a resistive divider. > This will allow more accurate P-P voltages in the Coil while > running....hopefully anyway. Power factor correction may also be > tried depending on how things go. > > I'm open for suggestions on any improvements, or experiments > if anyone has any. > > snip... > >> >Consider Kevin's coil. His pig combo rating is 14.4kV at 20kVA. > >His > >> >cap is 0.138uF or something similar. He draws 100 amps from a > >> >240 volt line. He runs at 120 bps. I just did the calcs, and a > >> >matched sized cap for Kevin's coil would be 0.31uF or so, and a > >> >typical LTR sized cap would be about 0.6uF or so. This is huge > >> >cap, and I don't recommend anything that large. His cap seems to > >> >be less than 1/2 the resonant size. (If you calc the reso-size > >> >based on the pig's specs.) You may want to check my calcs here > >> >in case I made an error. But if his reso-size would be 0.31uF, I > >> >certainly would not suggest using anything larger than 0.375uF or > >> >so. Since Kevin's cap may be about 1/2 the reso-size, it's > >> >possible that his power factor might not be that good, but I have > >> >no real idea if it is or not. It is also > > > >> >possible that Kevin's coil may work much better with a 0.375uF > >> >cap, if it greatly improves the power factor. It's too bad we > >don't > >> >know what the power factor is on Kevin's coil. Then again, it is > >> >possible that a reso or LTR cap is NG for a big coil. It may > >hurt > >> >the quenching too much or something, who knows. Maybe > >> >someday someone will build a big coil with LTR. > >> > >> Forgive as I think out loud about Kevin's coil... > >> > >> 240 volts at 100 amps gives us 24000 watts. We'll assume we can > >add power > >> factor caps until the PF is good and we can use all 24kVA. > >> > >> 24000 / 120BPS gives a 200 Joules per bang. The firing voltage > >> for > >a > >> 14.4kV transformer is 14400 x SQRT(2) = 20365 volts. 200 Joules = > >> > >1/2 x C > >> x V^2 so the LTR cap size is 964.5nF. Yeah!! :-)) > >> > >> If his present coil is running 138nF then he would have to > >> increase > >the BPS > >> to match the LTR case. 120 x 964.5 / 138 = 839BPS. However that > >is async! > >> There for he instantly has to double that to match the sync case > >for 1677 > >> BPS (async gaps deliver 1/2 the power of sync gaps of the same BPS > >> > >do to > >> firing on less than full voltage). > > > >You're assuming that his firing voltage will remain constant > >regardless > >of the cap size. If this were true, Kevin's coil (0.138uF) would be > >drawing only about 3430 watts at 120 bps, (not counting losses). Yet > >his coil > > > >draws 24kVA or so! To me, the only explanation is that his firing > >voltage must be much much higher than 20365 volts, due to a ballast > >setting that gives some degree of resonant charging. Although the > >power factor may not be perfect, I don't think the true watts drawn > >is only 3430 watts. If he was using only 3430 watts now, I don't > >think he would be getting 24 foot sparks. So to me, this is a > >reality check.... his caps must be firing at a much higher voltage > >than 20365. I believe that resonant charging must often be > >considered when analyzing low bps pig powered coils. Otherwise > >things just don't add up. > > > >Kevin is using a combo of two ballasts, I believe, and it is possible > >that the ballast is lossy. I know that when I used a variac as a > >ballast on my small coil, it doubled the input VA, for the same spark > >length. I think Kevin said that his ballast gets quite hot, so it > >may be burning some power, but I have no idea how much. If we assume > >that his ballast burns up 3000 watts, and his other wiring and xfmer > >losses are 5% more or another 1000 watts, then he'd be supplying > >still about 20kVA to the system. If the power factor is only 70%, > >then his true wattage would be about 14kW. This would mean that his > >bang size is 117 Joules at his present 120 bps. This is much larger > >than the 28 Joules that is predicted if one uses 20365 volts as the > >firing voltage. Now if one uses 37kV for the firing voltage, then a > >figure of 97 Joules per bang is obtained, which seems to fit his > >situation better. It's still not 117 Joules, but his losses may be > >even higher than I figured, which would explain the difference. Or I > >may have made a mistake, and his total input VA may be 20kVA, not > >24kVA. If this is the case, it would drop his bang size to 97 > >Joules, which would match up with a 37kV firing voltage. Another > >thing that makes me think that my analysis is correct, is that it > >agrees with Greg Leyh's results. Greg has posted his firing > >voltages, etc., so we kind of know the bang size vs. spark length > >relationship. We know for instance that 3430 watts cannot give 24 > >foot sparks at 120 bps. > > > Freezing in Oklahoma > > Kevin E. > > > > > > > > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > http://dl.www.juno-dot-com/get/tagj. > > > >

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