How does a brushless motor work?

The brushless DC motor uses semiconductor switching devices to realize electronic commutation, that is, replacing traditional contact commutators and brushes with electronic switching devices. It is characterized by high reliability, no commutation sparks, and low mechanical noise, and is widely used in high-end recording consoles, video recorders, electronic instruments and automatic office equipment.

The brushless DC motor studied in this paper includes permanent magnet rotor, multi-pole winding stator, position sensor and so on. By changing the position of the rotor winding position, the current of the stator winding is commutated in a certain order. The operating voltage of the stator winding is provided by an electronic switching circuit controlled by the output of the position sensor.

There are three types of position sensors: magnetic, photosensitive, and electromagnetic.

The brushless DC motor uses a magnetic-sensitive position sensor, and its magnetic-sensitive element is installed on the stator assembly to detect the change of the magnetic field generated by the rotation of the permanent magnet.

The brushless DC motor adopts a photoelectric position sensor, and the photoelectric sensor is arranged on the stator assembly according to a specific position. The shading plate is installed on the rotor, and the light source is an LED lamp or a small light bulb. When the rotor rotates, due to the action of the shading plate, the photosensitive element on the stator generates a pulse signal at intervals of a certain frequency.

The brushless DC motor adopts an electromagnetic position sensor, and an electromagnetic sensor element is installed on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect causes the electromagnetic sensor to generate a high-frequency modulation signal.