Andres125sx wrote: ↑
Wed Jun 05, 2019 10:31 am
... Increased resistive losses are almost negligible, and fall in magnet performance only comes at very high temperatures which are not reached in normal conditions, only if extremely overheating the motor ....
+100 deg C will increase armature resistance (so resistive losses) by 35 - 40%
+100 deg C will reduce magnet flux density by 5 - 20%
correspondingly changing torque constant and voltage constant (analogous to mechanically changing gear)
and magnetic field strength is reduced by the magnetic field produced by current flow - this is 'armature reaction'
(enough AR can wholly or partially permanently demagnetise the magnets - high temperature isn't necessary)
changing torque constant and voltage constant will need closed loop eg rpm control
to give the motor when hotter the necessary greater current for a given torque demand
to give the motor when hotter the necessary greater voltage for a given rpm demand
and there will be some cost for this paid by the battery and/or what comes between the battery and the motor