An engine can never function if it is designed exclusively with permanent magnets. This factor is easy to see, since not only will there not be the initial torque to start the movement, if they are already in their equilibrium positions, they will only oscillate around that position if they have an initial push. To operate properly, the motor rotor requires torque so that it can start its rotation.
This torque is normally generated by magnetic forces developed between the magnetic rotor poles and those found in the stator. The attraction or repulsion forces, developed between stator and rotor brake motors, can pull or push the movable poles of the rotor, thus producing torques, which will cause the rotor to rotate faster, until the frictions or charges attached to the rotor. shaft can reduce the resulting torque to zero.
After this point, the rotor will rotate with constant angular velocity. Both the rotor and the stator of the motor must be magnetic, since these forces between the poles produce the necessary torque to make the rotor rotate. However, even if permanent magnets are often used, especially small motors, at least some of the magnets on an engine will need to be electromagnets.