David Kronstein wrote:
The waveforms are a composition of three sinusoids. One is the fundamental of the excitation and the other two the natural frequencies of the "double resonance" network. In certain conditions they really combine destructively. I discuss this here:<div class="moz-text-flowed" style="font-family: -moz-fixed">Hi All,I was working on tuning my DRSSTC (coil details at http://4hv.org/e107_plugins/forum/forum_viewtopic.php?63284), and I notice that the primary current goes very suddenly into a "notch" mode when moving the tap point. I've taken a series of scope shots of this and made a couple of animated GIFs.Condtions: 100VDC bus, single shot, some breakout into air, ~1' sparks. 200A/div current, interrupter output shown on scope.This one shows a relatively wide range of primay turns, ranging from 3 11/12 to 4 9/12 turns, 1/12 turn per step:http://4hv.org/e107_files/public/1235287411_347_FT63284_wide_range.gifThere's a very sudden change early on. I tried to take more steps, shown in the shot below, but the transition point is somewhere in the middle of the primary support, so I can't take extra shots in between. 4 2/36 to 4 7/36 turns in 1/36 turn steps.http://4hv.org/e107_files/public/1235287411_347_FT63284_narrow_range.gifWhy do these sudden changes occur with changing tap point? And what would you generally recommend for setting the best tap point? I've heard people say to tune the primary about 10% lower than the secondary.
http://www.coe.ufrj.br/~acmq/tesla/drsstc.htmlWhen you change the tap point you change the natural frequencies of the network, and the notches appear and disappear. Changing the coupling between the coils makes the notches appear more or less spaced. You can use the notches to minimize the required primary current for a given output. The best tuning point probably can be found by the procedure: Adjust the coupling between the coils and look for the complete beats by adjusting the primary tap until the highest primary current on the first "beat" is as high as you think that is safe. But do not decrease the coupling too much (leave about 20 cycles in the beat at most), or the tuning becomes too critical. If the maximum current in the first beat is still low, you can use the maximum current on the second or third, but this indicates that your primary capacitor is too small. The driver must be switched off at the center of the first beat, or of the beat when the maximum current is reached. With heavy streamer loading, the ideal tuning may be somewhat different, but this is a good starting point.
Antonio Carlos M. de Queiroz _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla