Hall sensor in brushless DC motor

by:V&T Technologies     2020-01-23
The working principle of brushless DC motor is essentially similar to that of Brush Motor. Brush DC motor uses mechanical brush and commutator to reverse the current in winding. The brushless motor uses electronic mode to reverse the winding current. Torque in DC motor is generated by the interaction between permanent magnet magnetic field and current in winding. In Brush Motor, commutator realizes the commutation of armature current and appropriate magnetic field by switching armature winding. In the brushless DC motor, the hall position sensor detects the position of the rotating magnetic field of the rotor and excites the corresponding winding through logic and drive circuit. In general, the winding reacts according to the magnetic field of the permanent magnet of the motor, thus generating the required torque. When the permanent magnet rotated by the brushless DC motor rotates over the Bipolar digital Hall sensor, the state of the Bipolar digital Hall sensor will change. In the 8-pole magnet brushless DC motor shown in the above figure, every two poles are 90 degrees apart, and Hall sensors are placed 120 degrees apart. At this time, the electrical angles between Hall sensors are 30 degrees apart. When the South Pole approaches, the bipolar digital Hall sensor changes to the working state. When the first digital Hall sensor changes to the working state at an electric angle of 0 degrees, the second digital Hall sensor works at an electrical angle of 30 degrees and the third digital Hall sensor works at an electrolysis of 60 degrees. When the North Pole passes through the Bipolar digital Hall sensor, the digital Hall sensor will turn into a release state, and the distance between each north pole of the rotating 8-pole magnet and the adjacent South Pole is 45 degrees. Therefore, after the magnet rotates 45 degrees, the digital Hall sensor will change from the working state to the release state. The output of the above three Bipolar digital Hall sensors is used as an encoder for rotor position, and the position and polarity information of the magnet are sent to the logic circuit as signals for switching off the H-shaped bridge power tube. The selection of digital Hall components for brushless DC motors shall be based on the installation requirements (The rotor magnetic field orientation) With the induction direction of Hall element, reasonable selection is made. TAG
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