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What is a brushless motor

Views: 118     Author: Holry Motor     Publish Time: 2022-06-17      Origin: Site

The brushless DC motor consists of a motor body and a driver, and is a typical mechatronic product. Because the brushless DC motor operates in a self-controlled manner, it will not add a starting winding to the rotor like a synchronous motor with heavy-load starting under variable frequency speed regulation, nor will it cause oscillation and loss of step when the load changes suddenly. The permanent magnets of small and medium-capacity brushless DC motors are now mostly made of rare-earth neodymium-iron-boron (Nd-Fe-B) materials with high magnetic energy levels. Therefore, the volume of the rare earth permanent magnet brushless motor is reduced by one frame size compared with the three-phase asynchronous motor of the same capacity.


working principle

The brushless DC motor uses 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 commutation sparks, and low mechanical noise, and is widely used in high-end audio recorders, video recorders, electronic instruments and automated office equipment.


The brushless DC motor consists of a permanent magnet rotor, a multi-pole winding stator, and a position sensor. The position sensor commutates the current of the stator winding along a certain order according to the change of the rotor position (that is, detects the position of the rotor magnetic 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 switch circuit, and switch the winding current according to a certain logical relationship). 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, photoelectric and electromagnetic.


A brushless DC motor using a magneto-sensitive position sensor, its magneto-sensitive sensor devices (such as Hall elements, magneto-sensitive diodes, magneto-sensitive pole tubes, magneto-sensitive resistors or special integrated circuits, etc.) To detect changes in the magnetic field generated by the rotation of permanent magnets and rotors.

The brushless DC motor using the photoelectric position sensor is equipped with photoelectric sensor devices at a certain position on the stator assembly, the rotor is equipped with a shading plate, and the light source is a light-emitting diode or a small light bulb. When the rotor rotates, due to the action of the shading plate, the photosensitive components on the stator will intermittently generate pulse signals at a certain frequency.


The brushless DC motor with electromagnetic position sensor is equipped with electromagnetic sensor components (such as coupling transformer, proximity switch, LC resonance circuit, etc.) on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will make the electromagnetic sensor Generates a high frequency modulated signal (whose amplitude varies with rotor position)