Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx> Hi Skip,I was running numbers and was about to get close to what you show minus coupling. I showed about 1.6 times higher and likely due to not having your actual inputs, etc.. Anyway, the cap death isn't a shock. Your lucky the NST didn't fail on 1 side (or did it?). Anyway, I'm curious as to what your trying to accomplish running at resonance on such a short 1:1 h/d high Q coil? If you get a cap that can take the higher voltage, you know the NST will be the next death. Don't get me wrong, I like it when coilers go out there and do something different. Just curious what your up to as know you've been coiling for quite a while now.
I have a coil similar to yours also using 18g and a helical primary with about 4 turns. However, coupling is about .3 or so. It was used as a maggy driver where the 3rd coil is directly over the top of the driver. This coil also used an aluminum disc between the driver and the 3rd coil (corona/breakout prevention from L2). The 3rd coil was just a small 4.5" coil but used a 9" x 30" topload. No problems breaking out. I insulated L1 to L2 with LDPE sheeting to prevent arc-over. I used Javatc to figure out the necessary L's and C's, but it took some creativity to force the program to model a 3rd coil. Freaked me out when it actually worked! The whole idea there was to consolidate a maggy, but in doing so, the 3rd coil affects the driver (just as a primary affects the secondary of a classic 2LC system and just as a topload affects a secondary [lot's of stuff to consider there]). It's a true 3LC disruptive coil with all the bells and whistles. This showed me that numerous coil stacks and inductances could be configured to model a single resonant frequency (obvious conceptually and mathematically, but proved mechanically when it actually worked).
http://www.classictesla.com/photos/hybrid/hybrid.html Take care, Bart Tesla list wrote:
Original poster: Skip Greiner <skipg@xxxxxxxxxxxxxxx> Hi AllWell I finally get some power into this proposed 1/4/wave unit. The final specs are as follows:Secondary Dia: 18 x 24 Winding length: 19.25 Wire: #18ga with plastic coating giving diameter of about .067 Turns: about 285 Wire length: 1366' which is about 227khz at 1/4 wave JAVATC resonance: 227 khz Resonance (measured, un-powered): about 226 khz Operating frequency (measured, powered): about 210 khz Top load: NONE (see below) Primary Dia: 22.5 Turns: 4 Wire dia.: .375 Cap: .034 JAVATC Resonance: 205khz Break: SRSG, 1800rpm, 4 pole Tranny: 9kv @ 120ma NSTIn order to reduce the racing sparks the secondary had to be elevated with the lower turn of the secondary about 4.5" above the top turn of the primary. Per JAVATC this reduced the k to .135In order to reduce the corona from the top turn of the secondary, a 0.5" strip of aluminum foil was placed about 4.5" above the top turn of the secondary and the final turn of the secondary was tied to it. This went all the way around the secondary form.Prior to literally blowing up the primary capacitor a ring of 36" streamers was produced all the way around the aluminum foil. Strikes exceeding 40" happened about 40% of the time.I was operating at about 65 to 70 volts input at this point. The input current as measured by an iron vane AC ammeter was about 25A. No pfc.The cap literally blew up at this point and so ended the day. I will now start to build an MMC and try to increase the coupling and run the tranny up to 120v input.Skip