The working principle of brushless motor

Brushless DC motors use 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 reversing sparks, and low mechanical noise. It 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 order according to the change of the rotor position (that is, detecting the position of the rotor pole relative to the stator winding, and generating a position sensing signal at a determined 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 the electronic switch circuit controlled by the position sensor output.

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 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 on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will cause the electromagnetic sensor to generate high-frequency modulation signals (the amplitude of which varies with the rotor position). Variety).

The choice of brushless motor

Brushless DC motors are widely used in AI intelligence, automobiles, medical equipment, industrial automation and other industries due to the characteristics of long life, low noise, and high torque. Because of their different specifications and types, how to choose brushless DC motors? It is very important to meet product performance requirements.

1. Specification selection

In the occasions where the power supply voltage is adjustable, the specifications of the brushless DC motor whose torque and speed are close to the corresponding rated values of the product can be selected according to the actual needs, and the required speed can be obtained by changing the voltage; When the brushed DC motor is available for selection, the appropriate specifications can be selected according to the torque first, and the voltage and speed of the product can be adjusted appropriately.

2. Power selection

The maximum power output of the motor is limited. If the power of the brushless motor is selected too small, the motor will be overloaded if the load exceeds the rated output power. When the load is overloaded, the motor will generate heat, vibration, speed drop, abnormal sound, etc., serious When overloaded, the motor will be burnt. If the power is too large, it will cause economic waste. Therefore, it is very important to choose the power of the motor reasonably.