On 12/26/2009 11:06 PM, Stephen A. Lawrence wrote: > > On 12/26/2009 07:34 PM, Terry Blanton wrote: > >> I have built a myriad of pulse motors and do not understand what CEMF >> means. Can you explain what to look for? >>
I used a lot of words below. In short, integral(CEMF * current * dt) = net mechanical energy out, for a conventional motor which plays by the usual rules of the game. In contrast, if TVD is the total voltage drop across the motor, then integral(TVD*current*dt) = total energy out (heat+mechanical), and is what should be measured if you put the whole thing in a calorimeter (and let friction and turbulence turn the mechanical energy into heat for you). The portion of voltage drop due to resistance in the coils would be TVD-CEMF. Sean claims CEMF=0 in his motor, but mechanical power out > 0. Consequently if you put his motor inside a calorimeter you'd find that integral(TVD*current*dt) < total energy out. This is apparently a first law violation (COE), not just second law; as far as I know Sean has not made the common magmo claim that some parts of the motor "get cold" during operation. [Aside: Has Naudin ever attempted and *failed* to repro *any* alternative energy claim? I get the impression his repro attempts *always* succeed, but perhaps I'm just ignorant...] > Voltage drop across a coil carrying a varying current, in a motor > subjected to a varying load. For a stationary coil it's just -L*dI/dt. > Of course if you're looking at battery voltage, you won't see the CEMF; > and in fact that's the main objection to Sean's demo. He didn't find > back EMF, but he didn't look very hard, either. To get a good > measurement you would need to simultaneously measure voltage drop across > the motor (or, better yet, an individual coil) along with current > through the motor (or coil), and if the inductance is small, you'd need > to look very carefully at the edges. Then look at how it changes as the > RPMs and the load change. > > Sean appears to have been measuring battery voltage and current through > one coil. The battery voltage droops slightly when the coil turns on. > Inductance of the coil is indeed apparently small, so the back EMF as > the B field builds up is hard to see in the scope traces the way Sean > had the thing set up -- but since he apparently didn't say exactly where > the probes were placed, and since I didn't study the comments carefully > or listen to the original video (just read a transcript), my comments > here should be treated with extreme caution. > > An experimenter who always distrusts his own results, as recommended by > various people on this list, would have tried a great deal harder to get > an accurate measurement of CEMF as the motor rotates than Sean appears > to have done, if I can judge by what I gleaned of his demonstration. > > > >> Terry >> >> On Sat, Dec 26, 2009 at 7:29 PM, Esa Ruoho <[email protected]> wrote: >> >> >>> http://jnaudin.free.fr/steorn/index.htm >>> >>> >> >> >
