From: "Terrell W. Fritz"
Date: Sat, 26 May 2001 18:35:31 -0600
Subject: Re: [TSSP] Topics on non-linear effects
Hi Paul, At 01:48 PM 5/26/2001 +0100, you wrote: >These topics listed below all share a common theme of exploring the >resonator load in the non-linear regime. There seems to be plenty of >qualitative understanding of what's going on, but I'd like to find >out what can be established quantitatively for certain situations, >particularly with a view to performance optimisation of traditional >Tesla coils. This kind of stuff is well outside my particular field >of expertise, so I'll post these notes as a kind of wish-list. >Personally, I'm fairly confident that the technical matters of modeling >the distributed currents and voltages of a coupled resonator are >manageable now, which shifts the emphasis over towards quantifying the >load dynamics in a way sufficient to close the loop on the modeling and >optimisation process. > >Time averaged load reactance >---------------------------- >We need to decide whether, in the CW/brush discharge regime, the load >resistance can be taken as a time averaged value, or whether in fact it >changes value significantly during an RF half-cycle. What sort of >error do we get if we assume a time averaged value? If it's too much, >we have to recompute things a number of times during each cycle, which >introduces its own source of (numerical) error over a number of cycles, >so we'd prefer to use a time averaged value, recomputed say, just once >per cycle. > >This boils down, I think, to measuring how close the topload voltage >and/or current waveform is to a sine wave. Do we get a noticeably >flattened top to the voltage waveform? I think the way to do this >would be to capture scope waveforms, extract a cycle or two at a time >and FT these. > >A similar question applies also to the load capacitance, which we >expect to increase as the coil voltage rises above a certain level. >Can this capacitance be time averaged over an RF cycle? > snip... I tried this one today. :-) All the data is at: http://hot-streamer.com/temp/TerryCW/2001-5-26/ A picture of the whole setup: http://hot-streamer.com/temp/TerryCW/2001-5-26/AllStuff.jpg The RF power supply. It was running 326kHz at 500 watts delivered real power (about 150 watts reflected, but the power supply compensates for that so 500 real watts was going to the coil). The harmonic distortion is >45 dB below the output fundamental sine wave: http://hot-streamer.com/temp/TerryCW/2001-5-26/RFPower.jpg The scope and calibrated fiber optic receiver: http://hot-streamer.com/temp/TerryCW/2001-5-26/ScopeFiber.jpg The plane Antenna Picking up the voltage off the coil (un calibrated but the signals are pure). http://hot-streamer.com/temp/TerryCW/2001-5-26/PlaneAnt.jpg The top electrode (Marc, that works super good!!) and current transducer to fiber optic: http://hot-streamer.com/temp/TerryCW/2001-5-26/CurrentProbe.jpg The coil: http://hot-streamer.com/temp/TerryCW/2001-5-26/CWCoil.jpg A bunch of arc pictures: http://hot-streamer.com/temp/TerryCW/2001-5-26/ArcASA400.jpg http://hot-streamer.com/temp/TerryCW/2001-5-26/spark.jpg http://hot-streamer.com/temp/TerryCW/2001-5-26/flash.jpg I steadied my hand with the camera to take these and got few a little RF burns now from the currents in me going to the grounded antenna plane. The following data is time averaged over 8 waveforms so not good for FFT stuff but that is next... The current into the streamer (should be in mA not mV, forgot to set scope): http://hot-streamer.com/temp/TerryCW/2001-5-26/RealCurrent-500w.gif A data file of this waveform in "CSV" format. Two simple columns, first is time second is current. The scope capture saves 10000 data points. Paul has used CSV files so they should be no problem to convert. Nothing fancy, just numbers: http://hot-streamer.com/temp/TerryCW/2001-5-26/RealCurrent-500w.CSV Both the voltage and current waveforms: http://hot-streamer.com/temp/TerryCW/2001-5-26/IandV-500w.gif Voltage data file of above: http://hot-streamer.com/temp/TerryCW/2001-5-26/V-500w.CSV Current data file of above: http://hot-streamer.com/temp/TerryCW/2001-5-26/I-500w.CSV I made a movie with the camera that turned out in MOV format. It is big and not real good so don't worry about it but it is there if interested: http://hot-streamer.com/temp/TerryCW/2001-5-26/P5260010.MOV For FFT stuff here is more raw data: A single capture of the waveforms: http://hot-streamer.com/temp/TerryCW/2001-5-26/Tek00000.gif The tops of these waveforms appear rough as if that is where streamer formation or something "tricky" is going on. It appears that the current or voltage is 180 degrees out of phase. I'll have to check that transducer to see if it is wired backwards. Or, the thing looks really inductive... The current data: http://hot-streamer.com/temp/TerryCW/2001-5-26/Tek00001.gif http://hot-streamer.com/temp/TerryCW/2001-5-26/TEK00002.CSV The voltage data: http://hot-streamer.com/temp/TerryCW/2001-5-26/Tek00002.gif http://hot-streamer.com/temp/TerryCW/2001-5-26/TEK00001.CSV Single cycle current and data: http://hot-streamer.com/temp/TerryCW/2001-5-26/Tek00003.gif http://hot-streamer.com/temp/TerryCW/2001-5-26/TEK00003.CSV Single cycle voltage and data: http://hot-streamer.com/temp/TerryCW/2001-5-26/Tek00004.gif http://hot-streamer.com/temp/TerryCW/2001-5-26/TEK00004.CSV Let me know if you want to see other waveforms or if more data is wanted somewhere. Today was mostly spent just setting this up and getting it to work. However, far greater detail and info is available depending on where one wants to go. Cheers, Terry
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.