Brushless DC motors use semiconductor switching devices to achieve electronic commutation, that is, electronic switching devices are used to replace traditional contact commutators and brushes. It has the advantages of high reliability, no reversing sparks, low mechanical noise, etc., and is widely used in high-end audio jacks, video recorders, electronic instruments and automated office equipment.
The brushless DC motor is composed of a permanent magnet rotor, a multi-pole winding stator, and a position sensor. The position sensor commutation of the stator winding current in a certain sequence according to the change of the rotor position (that is, it detects the position of the rotor pole relative to the stator winding, and generates a position sensing signal at a certain position, which is processed by the signal conversion circuit To control the power switch circuit, switch the winding current according to a certain logical relationship). The working voltage of the stator winding is provided by an electronic switch circuit controlled by the output of the position sensor.
There are three types of position sensors: magnetic sensitive, photoelectric and electromagnetic. Brushless DC motors using magnetic-sensitive position sensors, whose magnetic-sensitive sensor components (such as Hall elements, magnetic diodes, magnetic sensitive pole tubes, magnetic resistors or application-specific integrated circuits, etc.) are mounted on the stator assembly. To detect the change of the magnetic field generated when the permanent magnet and the rotor rotate.
The brushless DC motor with photoelectric position sensor is equipped with a photoelectric sensor at a certain position on the stator assembly, a light shield is installed on the rotor, and the light source is a light emitting diode or a small bulb. When the rotor rotates, the photosensitive components on the stator will generate pulse signals intermittently at a certain frequency due to the effect of the light shield.
Brushless DC motors using electromagnetic position sensors are equipped with electromagnetic sensor components (such as coupling transformers, proximity switches, LC resonance circuits, etc.) on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will cause the electromagnetic sensor Generate high frequency modulation signal (its amplitude changes with rotor position).
