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Application prospect of brushless DC motor

Permanent magnet brushless motor is a closed-loop mechatronics system, which uses the rotor pole position signal as the signal of electronic switch circuit. Therefore, accurate detection of the rotor position and timely switching of power devices according to the rotor position are the keys to the normal operation of brushless DC motor.Using position sensor as rotor position detection device is the most direct and effective method.Generally, the position sensor is installed on the shaft of the rotor to realize the real-time detection of the rotor position.The earliest position sensors were magnetoelectric, bulky and complex, and obsolete;At present, the hall position sensor with magnetic sensitivity is widely used in brushless DC motor, and there are also photoelectric position sensors.The existence of position sensor increases the weight and structure size of brushless DC motor, which is not conducive to the miniaturization of motor.When the sensor is rotated, it is hard to avoid wear and difficult to maintain.At the same time, the installation precision and sensitivity of the sensor directly affect the running performance of the motor;On the other hand, because of too many transmission lines, it is easy to introduce interference signals.Because it is the hardware to collect the signal, the reliability of the system is reduced. In order to adapt to the further development of brushless DC motor & brushless AC motor without position sensor, it usually use induction counter electromotive force of the armature winding to indirect rotor magnetic pole position, compared with direct agglutination test, get rid of the position sensor, simplifies the motor ontology structure, has obtained the good effect, and has been widely used.