What Is A Brushless DC Motor?

- Jun 22, 2018 -

What is a brushless DC motor?


Auto Door Openers.jpgBrushless DC motors use semiconductor switching devices to achieve electronic commutation, that is, electronic switching devices replace traditional contact commutators and brushes. It has the advantages of high reliability, no commutation sparks, low mechanical noise, etc. It is widely used in high-grade recording seats, video recorders, electronic instruments and automation office equipment. Brushless DC motors consist of permanent magnet rotors, multipole winding stators, and position sensors. Position sensing changes the current of the stator winding along a certain sequence according to the change of the rotor position, that is, detects the position of the rotor pole relative to the stator winding, and generates a position sensing signal at a determined position, which is processed by the signal conversion circuit. To control the power switch circuit, according to a certain logic relationship to switch the winding current. The operating voltage of the stator winding is provided by an electronic switch circuit controlled by the position sensor output.

A brushless DC motor using a magnetically sensitive position sensor has a magneto-sensitive sensor element mounted on a stator assembly for detecting a change in the magnetic field generated when the permanent magnet and the rotor rotate. A brushless DC motor adopting a photoelectric position sensor has a photoelectric sensor arranged on a stator assembly at a certain position. A shading plate is mounted on the rotor, and the light source is a light emitting diode or a small light bulb. When the rotor rotates, due to the action of the shading plate, the photosensitive components on the stator will generate pulse signals intermittently at a certain frequency. A brushless DC motor adopting an electromagnetic position sensor is equipped with an electromagnetic sensor component on the stator assembly. When the position of the permanent magnet rotor changes, the electromagnetic effect will cause the electromagnetic sensor to generate a high-frequency modulation signal.


The general brushless DC motor essentially belongs to a servo motor, which is composed of a synchronous motor and a driver and is a variable frequency speed control motor. Variable-voltage speed-regulated brushless DC motors are truly brushless DC motors.