Brushless DC motor has the characteristics of a DC brushed motor and is also a device of frequency change, so it is also called DC frequency conversion, and the international common term is BLDC. The DC brushless motor is relative to the brush motor. The rotor of a brushed motor is a coil winding, which is connected to the power output shaft, and the stator is a permanent magnet magnet; the rotor of a brushless DC motor is a permanent magnet magnet, which is connected to the output shaft together with the casing. The stator is a winding coil. The brush motor is used to alternately change the commutation brushes of the electromagnetic field, so it is called a brushless motor.

Anyone who uses a brushless DC motor is familiar with position sensors. So what is the role of the position sensor? What is the principle?

The position sensor plays a role in determining the position of the rotor magnetic pole in the DC brushless motor, and provides the correct commutation information for the logic switch circuit, that is, the position signal of the rotor magnetic steel pole is converted into an electrical signal, and then the commutation of the stator winding is controlled. There are many types of position sensors, and each has its own characteristics. There are three types of position sensors commonly used in brushless DC motors: electromagnetic position sensors, magnetic-sensitive position proximity sensors, and photoelectric position sensors.

(1) In the DC brushless motor, the electromagnetic position sensor is the open transformer. The split transformer used for three-phase brushless DC motors is composed of a stator and a tracking rotor. The stator generally has six poles, with an interval of 60 degrees between them. Three poles are wound with a primary winding and connected in series with each other to provide high-frequency power. The other three poles are wound with secondary windings WA, WB, WC.

(2) Magnetic-sensitive position sensor refers to a semiconductor sensitive element whose electrical parameters change with the surrounding magnetic field according to certain rules. The basic principles are Hall effect and magnetoresistance effect. Common magnetic sensors include Hall element or Hall integrated circuit, magnetoresistor and magnetoresistive diode.

(3) The photoelectric position sensor is made of photoelectric effect, and it is composed of a light shield that rotates with the motor rotor, a fixed light source, a photoelectric tube and other components.

The brushless DC motor is a high-tech product that integrates motor, microelectronics, control, and computer technologies. Brushless motors are widely used in high-precision control industries such as medical, industrial control, automotive electronics and consumer electronics. With the development of power electronics and the emergence of new permanent magnet materials, the development of brushless DC motors is bound to be more rapid. In addition, the position sensor can detect the polarity of the motor rotor anytime and anywhere, which is more conducive to the full use and maintenance of the DC brushless motor.