Brushless DC motor uses the semiconductor switching devices to achieve electronic commutation, which uses electronic switching devices replace the traditional contact commutator and brushes. It has high reliability, no commutation spark, and low mechanical noise, widely used in high-end tape deck, video recorders, electronic equipment and office automation equipment.
Brushless DC motor comprises a permanent magnet rotor, multi-pole stator winding, position sensors and other components. According to the change of rotor position, position sensors convert the current of stator windings along a certain order (i.e., detect the position of rotor poles relative to the stator winding, and generating position sensor signal at the location determined, through the signal conversion circuit processing to control the power switching circuit, according to certain logical relationship to switch the winding current). Operating voltage of stator windings provided by electronic switching circuit controlled by the position sensor output.
There are magnetic position sensors, photoelectric and electromagnetic three types.
Using magnetic position sensor, the brushless DC motor, its magnetic sensors (such as Hall elements, magnetic diodes, magnetic resistance, or ASIC, etc.) are mounted on the stator assembly, which is used to detect the magnetic field change generated while permanent magnet, rotor is rotating.
Using photoelectric position sensor in the brushless DC motor, the stator assembly are mounted photoelectric sensor pieces according to a certain location, visor is mounted on the rotor, the light source is a light emitting diode or a small light bulb. When the rotor rotates, because of the shading plate, sensitive components on the stator will generate a pulse signal according to a certain frequency. Brushless DC motor with magnetic position sensor, electromagnetic sensor components (for example coupling transformers, proximity switch, LC resonant circuits, etc.) is mounted on the stator assembly, when the position of permanent magnet rotor changes, electromagnetic effects will lead electromagnetic sensor generate high-frequency modulated signal (the amplitude varies with rotor position).
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