Brushless DC Motor
Brushless DC MotorIts adopts semiconductor switching device to realize electronic commutation, i.e. electronic switching device instead of traditional contact commutator and brush. It has the advantages of high reliability, no commutation spark, low mechanical noise, etc. It is widely used in high-grade recording docks, video recorders, electronic instruments and automatic office equipment.
Brushless DC motor is composed of permanent magnet rotor, multi-pole winding stator, position sensor, etc. The position sensing switches the current of the stator winding along a certain sequence according to the change of rotor position (i.e. detects the position of the rotor pole relative to the stator winding and generates a position sensing signal at the determined position, which is processed by the signal conversion circuit to control the power switching circuit to switch the winding current according to a certain logic relationship). The working voltage of the stator winding is provided by the electronic switching circuit controlled by the output of the position sensor.
There are three types of position sensors: magnetic, photoelectric and electromagnetic.
Brushless DC motors with magnet-sensitive position sensors have magnet-sensitive sensor components (such as Hall elements, magnet-sensitive diodes, magnet-sensitive exodes, magnet-sensitive resistors or special integrated circuits, etc.) mounted on the stator assembly to detect changes in the magnetic field generated by the permanent magnet and rotor rotation.
Brushless DC motor with photoelectric position sensor is equipped with a photoelectric sensor in a certain position on the stator assembly, and the rotor is equipped with a light shield, and the light source is a light-emitting diode or a small light bulb. When the rotor rotates, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency due to the role of the light shield.
Brushless DC motors with 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 rotor position of the permanent magnet changes, the electromagnetic effect will cause the electromagnetic sensor to generate a high frequency modulated signal (its amplitude varies with the rotor position).