On 02/09/2010 08:25 PM, Abd ul-Rahman Lomax wrote: > At 04:40 PM 2/9/2010, you wrote: >> Lovely page! Thanks, Harry! >> >> JLN has done a really clear job of describing the effect, well enough >> that it can be reproduced and fully analyzed, with, as far as I can see, >> no hidden tricks. > [ ... ] > > But measuring that turn-on and shutdown energy isn't particularly > simple. Those are high-speed transients, and determining the energy in > them simply by watching them on a scope display isn't going to cut it.
I'm not so sure. Just getting a ballpark measurement would be interesting. Naudin's scope was just loafing along for those shots, and even so, if you look closely you can see right on his screen shots that electrical energy consumed is going to be higher in a running motor than a stopped motor. If JLN put the power display into A-B mode you'd get something pretty telling, I think. If the sample rate were cranked up, and just the edges examined, you'd be in the ballpark for getting some real energy measurements for the turn-on/turn-off pulses. Sean may claim he's got something else going on, too, of course, beyond what JLN is showing. But what JLN shows is interesting all by itself. Naudin, unlike Sean, is into documenting everything, so recreating Naudin's experiment should be straightforward. > > Remember, Sean has insisted that he needs the rapid response of the kind > of battery he is using, an ability to source large currents. Why? > Obviously, large peak currents are needed! Large peak currents? Going through an inductor? Do tell! I didn't swallow that business about the battery when Sean said it and I don't believe it now. Large peak voltages when the circuit's opened, sure, I can buy that. But one thing inductors do really well is squash the current peaks. Look at Naudin's scope shots -- no wild peaks in the current, and I don't think that's because he "lost" them somewhere. They were never there to begin with. L * dI/dt = V I = integral(V/L) dt. In other words, you need a nice high voltage for a good long while to get a really hefty current to flow through an inductor. Forget Sean's high *current* transients, they're not happening.
