Can i ask would you say that your avalanche mode of operation is causing noise bursts, bit like a burst of white noise.Pulses of varying mark and spacing.
No not white noise, but pulse period follows (is modulated by) the curve of the top of the ringing choke waveform. I burned the midnight oil in trying to get a handle on what was happening with my original setup. I was able to replicate it in the lab last night, but my findings show that the violent excursions were due to two things: 1) The ringing choke caused high voltages in excess of the avalanche breakdown of the SCR. This generated currents into the bifilar at least double the steady state firing mode. Last night I saw currents as high as 1000 amps. This is partly due to the fact that I had to change out the SCR, as the original was blown from an accidental short. The replacement had an even higher avalanche threshold than the original. 2) The bifilar wires interact with the circuit in a manner that helps create the avalanche condition. But this is not due to any feedback of excess energy as I originally thought.As the wires separate from an initial repulsion, the inductance increases and this shows up as a decrease load on the secondary of the matching transformer which pushes the ringing voltage higher and closer to avalanche. You can see this by watching the amplitude of the pulse as the wires are separated manually. It is easy to see that a relaxation oscillator can occur from this arrangement. When the burst occurs, the power supply takes some time to recover charge into the primary storage capacitor. As this voltage climbs, the ringing choke peak voltage starts approaching avalanche then a burst occurs when it hits avalanche. The original waveform drawing I made is correct but does not show the magnitude of voltage and current being generated by the ringing choke, as my scope probe wouldn't support the division required to keep the image on screen. I had to use a small divider 10 to 1 on top of the probes 10x setting. Total casualties on this project included 2 power supplies and 3 expensive SCR's. I was able to repair the power supplies. One of the SCR's failed in an unusual way, it became a power diac with a 200 volt breakdown. The next step, if there is one, would be a better pulse gen circuit that is not affected by the changing inductance of the wires as they repel. We have identified and fairly thoroughly analyzed the mechanism that created the violent excursions. If there is any value in tapping into the parametric inductance and possible OU as EM suggested, it will require a rethink of how this might be done. Attached is the configuration I used last night.
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Topic: Replication of ION's bifilar (Read 96887 times)
