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. You also risk a fault in the drive shutting off all the fets/igbts while running near top speed, loosing the field weakening, back emf goes to full strength, and rectified voltage back through the bridge becomes MUCH higher than the DC bus can handle. Been there done that w/ a eurocopter APU starter we designed w/ Kollmorgen. They had to add an output contactor that opens for a drive fault. ------------------------------------------------------------------------------ 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
