From: Paul
Date: Mon, 28 May 2001 15:11:39 +0100
Subject: [TSSP] Time domain comparison
Hi All, Terry has captured scope traces of the secondary base current and I've compared these to the modeled response, see http://www.abelian.demon.co.uk/tssp/tfss270501/ I think we are getting a reasonable match with predictions of the response in the linear regime. Anyone who is unclear what we mean by precision modeling should now be getting the general idea :) Emphasis now is clearly on trying to quantify those non-linear effects. Thanks again to Bart, Terry, et al, for their efforts a few months back in checking the pri-sec M with acmi. As a result, I've been able to focus on other parts of the software and we can all just sit back and watch the k factor come out right. Terry, if you're keen to take some more of these measurements, it would be very interesting to see what happens to the mode spectrum as a) the primary tuning is moved away from optimum, b) the primary coupling is increased beyond its current setting, My speculation is that as we move away from the 'optimum' tuning, more and more of the initial bang energy goes into the unwanted higher modes. If we can demonstrate measured and modeled data for a handfull of adverse tuning situations, we may be able to tell if the resulting 3rd mode amplitude is enough to cause things like racing arcs, etc. I won't be able to process the data very quickly - back to work tomorrow for me (:, but if you store the traces I can gradually work through them. Terry, I think you were using more than 100V when you captured LowNoise.CSV, as I had to throw in a big scaling factor - were you at 500V ? The level of the higher modes surprised me and I treated it as a software error. After spending two whole weekends and a few evenings trying to make it go away, I eventually had to accept that the model might be telling us some- thing - after all, an interesting phenomena is indistinguishable from a soft- ware error, to begin with. Now, thanks to Terry's unequivocal current readings, I think that we can start to ask sensible questions about how the bang energy is divided up amongst the available modes, and just what the consequences of getting things wrong are. We can also set about examining how different shapes of primary affect the mode distribution, since ultimately these higher modes are struck into resonance by the difference in secondary profile between the two main 'operational' modes. I'll place another bet and suggest that, say, a cone primary, by virtue of its more evenly-spread application of EMF to the secondary, would result in the main two modes being more similarly shaped than with, say, a flat primary, and as a result it would be a little more robust with respect to mis-tuning or over- coupling. How much do these things matter? Who knows, but I think we have the tools to find out. Cheers All, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.