How does the brushless DC motor work?

The armature of an ordinary DC motor is on the rotor, and the stator generates a fixed magnetic field. In order to make the DC motor rotate, it is necessary to continuously change the direction of the current in the armature winding through the steering gear and the brush, so that the directions of the two magnetic fields are always perpendicular to each other, so as to generate a constant torque to drive the motor to continuously rotate.

In order to remove the brushes, the brushless DC motor puts the armature on the stator, and the rotor is made of permanent magnets. This structure is just the opposite of the ordinary DC motor; however, even this change is not enough, because the armature on the stator passes through the DC current. After that, only a constant magnetic field can be generated, so that the stator magnetic field can continuously change with the position of the rotor, so that the stator magnetic field and the permanent magnetic field of the rotor always maintain a left-to-right spatial angle, and a torque is generated to drive the rotor to rotate.