Eric, Did you lock the rotor? If you don't and just apply a field the motor will align to a stable N-S. Even at VERY high temps & fields you will not damage the magnets (you are actually trying to magnetize them even more - its how magnets are made afterall.) You need to lock the rotor (or use active field/orientation control) if using opposing forces just sitting still N-N & S-S as this is a highly unstable condition. Any tiny offset will generate Q axis forces and the rotor will *RAPIDLY* move to the stable N-S state. We never ruined a motor but were instructed by the motor designers that it can happen. No idea what the coercivity of a modern neodymium magnet is at typical motor operating temp.
On Thu, Jan 26, 2017 at 7:09 AM, Eric Keller <eekel...@psu.edu> wrote: > On Wed, Jan 25, 2017 at 11:22 PM, Stephen Dubovsky <smdubov...@gmail.com> > wrote: > > On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson <el...@pico-systems.com> > wrote: > > > >> Field weakening is not possible on permanent magnet > >> brushless motors. > >> > >> > > It actually is. Apply current in the D axis will oppose and reduce the > net > > flux in the gap. Move a coil in between two N poles permanent magnets > > facing each other and you will get no voltage as the field is zero at the > > center. You risk demagnetizing the magnets at high temp. > > We tried to do this for some fault detection research. We set the > winding currents so that the motor didn't move, but just heated > itself. No failures. There is enough change in the magnets with heat > that we could detect the changes, but they went right back to normal > when the temperature went back down. We were hoping to get some > degradation in the magnets over time, but it never happened. It was > disappointing and reassuring at the same time. I suppose we should > have gone higher with the current, because we never had any winding > failures either. The drive was made for a lot more current than the > motors could take. > > ------------------------------------------------------------ > ------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
