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Re: ScanTesla program - Lowering the coupling may be better...



Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Daniel.

I was meaning the main power variac setting. You said you adjusted it mechanically so you dont have the Freau controller. The main power variac setting will affect the phase of the charging waveform so you will need to readjust the firing phase of the SRSG as you increase the variac output and make a final adjustment at maximum output. As the main variac output is increased, the peak charging point will pull up in time and if the SRSG was only adjusted at medium variac output, this will have the effect of firing too late at maximum variac output and result in rough operation. Some power sources can saturate during this late timing thus reducing the effective inductance of the power source. This in turn can cause mains resonance even though you thought you were LTR (called ferroresonance). As the power source inductance decreases, the charging peak will also pull up in time and could cause the SRSG to stop firing entirely and result in uncontrolled resonant rise. Adjust your SRSG to fire sooner in the cycle until the roughness disappears and see if you still have racing sparks. See interspersed comments.


Original poster: Daniel Hess <dhess1@xxxxxxxxxx>


Hi Gerry;

motor under power, while the coil is operating. When I retarded the RSG motor (CCW) the performance of the coil increased dramatically but alas, eventually came the racing sparks and the cap safety gap began firing as I continued to retard.

This is exactly what I would expect. When you retard too much (too late in the cycle), the charging wavefore also happens sooner (increased current causes a different operating point on the B/H curve - beginnings of saturation and reduced inductance) and the SRSG starts to miss. Firing after peak can be unstable if retarded too much cause changes in the firing point also changes the timing of the charging waveform. Rough operation results and resonant rise causes the safety's to fire.



To answer your last question, the operation sounded rough, very rough to me. I attribute this to the fact that the cap safety gap was firing 'all over the place.' But then again, the safety gap firing is akin to a misfire; You would expect rough operation under those circumstances, yes?

To me, it is a chicken and egg problem. The misfire of the SRSG can cause the safety to fire. A safety firing occuring while the SRSG is operating normally can also cause the SRSG to misfire. A safety firing will introduce a transient response with a timing different then when the SRSG fires and screw up the charging waveform. In either case, rough operation will occur.


Gerry R.