Can external magnets disturb the magnetic field of an electric motor?

Question

I plan on mounting a small brushless motor using neodymium magnets. Would the external mounting magnet interfere with the weaker magnetic field generated in the motor?

If yes, does it apply also with induction and permanent dc motors?

Thanks!

Answer 1

Any kind of electromotor will be influenced by presence of strong external magnetic field. The reasons are:

• the motor usually contains heavy ferromagnetic parts, which both experience undesired force toward the external magnet and also change their magnetization in undesired way.

• even if there is no ferromagnetic material in the motor, the external magnetic field will induce uneven electromotive and also ponderomotive (mechanical) forces in the windings.

Depeding on the strength of the magnetic field, this may lead to deviation from smooth rotation to a jerky one, unbalanced forces having non-zero deviation moment will increase mechanical wear on the axis and sockets, possibly causing destruction of the motor (especially if the motor is run at high speeds).