On Mon, Jan 25, 2016, at 12:37 PM, Gene Heskett wrote: > On Monday 25 January 2016 08:00:12 Marius Alksnys wrote: > > > 01/24/2016 11:55 PM, Gene Heskett rašė: > > > On Sunday 24 January 2016 16:30:45 Marius Alksnys wrote: > > >> 01/24/2016 04:37 PM, Dave Cole rašė: > > >>> Is the positioning ability adequate? > > >> > > >> I am impressed how strong it holds in position even when fed with > > >> DC current (freq = 0). I can't force it to rotate by hand, while it > > >> is very easy rotating while turned off. > > > > > > That motors rotor has to be offcenter enough to drag under dc > > > exitation, whereas it should move like it was full of cold molasses. > > > Call a surveyer slow, but dead smooth. > > > > > > As that raises the spot heat from friction at low speeds, I'd want > > > to have a spare on the shelf in case it self destructs. > > > > Sorry Gene, it is hard for me understand almost all of your posts > > without dictionary and deeper analysis of your words.. It might be > > because my mother language is Lithuanian, my English technical is ~ > > ok, but your posts are full of colorful English.. :) > > And despite having some Iowegian neighbors while growing up, I am in the > same situation, I don't know a word of Lithuanian. I in fact, highly > appreciate that you have learned English well enough to write it quite > well, and I thank you for that effort. And if my posts > are "entertaining" because of some of the slang phrases I might use, > that I hope, is a Good Thing. > > > This spindle rotates at 10kRPM nicely, thus I have no doubts it is in > > good balance. I think heavy magnetic field holds the magnetized rotor > > almost in place when I turn 10A DC current on. > > If its not perfectly centered between the field poles, the magnetism will > pull it farther off center, flexing anything in the assembly that can be > flexed, far enough to drag on and stick to the poles. >
Some assumptions are being made here. Gene is assuming that this is an induction motor, which as he says should experience a smooth resistance proportional to speed when there is DC in the coil. I find it hard to believe that the motor would be so far off-center that it could start dragging. (I'm also making an assumption - that Marius's 10A DC current is within the motor rating.) Another explanation could be that the motor has a permanent magnet rotor. Such a motor doesn't slip. Under DC excitation it acts like a stiff spring. Again I'm assuming 10A is within spec, and that rated voltage is 230 or more, not some little 24V thing. That means it's a pretty decent sized motor, and the "spring" is quite stiff indeed. It could easily be impossible to turn by hand, especially if there is nothing but a shaft to grab. -- John Kasunich [email protected] ------------------------------------------------------------------------------ Site24x7 APM Insight: Get Deep Visibility into Application Performance APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month Monitor end-to-end web transactions and take corrective actions now Troubleshoot faster and improve end-user experience. Signup Now! http://pubads.g.doubleclick.net/gampad/clk?id=267308311&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
