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Working principle of brushless motor

2021-06-13 20:03:38 Volcano Motor Read

Brushless DC motor adopts semiconductor switching devices to realize electronic commutation, that is, electronic switching devices replace traditional contact commutator and brush. It has the advantages of high reliability, no commutation spark, low mechanical noise and so on.

Brushless DC motor is composed of permanent magnet rotor, multi-pole winding stator and position sensor. According to the change of rotor position, position sensing commutates the current of stator winding in a certain order (i.e., detects the position of rotor magnetic pole relative to stator winding, generates position sensing signal at the determined position, controls power switch circuit after being processed by signal conversion circuit, and switches winding current according to a certain logical relationship). The working voltage of the stator winding is provided by the electronic switch circuit controlled by the output of the position sensor.


Working principle of brushless motor

There are three types of position sensors: Magnetic sensor, Photoelectric sensor and Electromagnetic sensor.

1. Brushless DC motor with magnetic position sensor, whose magnetic sensing devices (such as Hall element, magnetic diode, magnetic diode, magnetic resistor or application specific integrated circuit, etc.) are installed on the stator assembly, which is used to detect the change of magnetic field generated when the permanent magnet and rotor rotate.

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

3. Brushless DC motor with electromagnetic position sensor is equipped with electromagnetic sensor components (such as coupling transformer, proximity switch, LC resonant circuit, etc.) on the stator assembly. When the position of permanent magnet rotor changes, electromagnetic effect will make the electromagnetic sensor generate high-frequency modulation signal (its amplitude changes with the rotor position).

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