How does a permanent magnet DC motor work

In order to rotate a permanent magnet DC motor, it is necessary to continuously change the direction of the current in the armature winding through a commutator and brush, so that the directions of the two magnetic fields are always perpendicular to each other, thereby generating a constant torque to drive the motor to rotate continuously. In order to remove the brushes, a permanent magnet DC motor places the armature on the stator, and the rotor is made into a permanent magnet. This structure is exactly the opposite of a regular DC motor; However, even this change is not enough, because the armature on the stator can only generate a constant magnetic field after passing through direct current, and the motor still cannot rotate. In order to make the motor rotate, it is necessary to continuously exchange phases and energize the stator armature windings, so that the stator magnetic field can constantly change with the position of the rotor, and the stator magnetic field and the permanent magnet magnetic field of the rotor always maintain a left and right spatial angle, generating torque to drive the rotor to rotate.