Advantages of brushless motor
Better torque speed characteristics can be obtained
High speed dynamic response
Brief introduction of brushless motor
Brushless DC motor is a typical mechatronics product, which is composed of motor body and driver. Because the brushless DC motor is operated by self-control, it will not add another starting winding on the rotor like the synchronous motor with heavy load starting under variable frequency speed regulation, and it will not produce oscillation and out of step when the load changes suddenly. At present, the permanent magnet of medium and small capacity brushless DC motor is mainly made of Nd-Fe-B material with high magnetic energy level. Therefore, the volume of rare earth permanent magnet brushless motor is one frame number smaller than that of three-phase asynchronous motor with the same capacity.
brushless motor diagram
Replace the traditional contact commutator and brush. 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 light 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 Produces a high-frequency modulation signal (the amplitude of which varies with the position of the rotor).
In terms of structure, brushless motors and brushed motors have similarities. There are also rotors and stators, but the structure is opposite to that of brushed motors; the rotor of brushed motors is a coil winding, which is connected to the power output shaft, and the stator is a permanent magnet. Steel; the rotor of the brushless motor is permanent magnet steel, which is connected to the output shaft together with the casing. The stator is a winding coil. The commutation brush used by the brush motor to alternately transform the electromagnetic field is removed, so it is called a brushless motor ( Brushless motor).
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