Development Status of Brushless DC Motors

The brushless DC motor not only maintains the good dynamic and static speed regulation characteristics of the traditional DC motor, but also has a simple structure, safe operation and easy control. Its application has developed rapidly from the initial military industry to aerospace, medical, information, home appliances and industrial automation.

Structurally, different from the brushed DC motor, the stator winding of the brushless DC motor is used as the armature, and the excitation winding is replaced by a permanent magnet material. According to the different current waveforms flowing into the armature windings, brushless DC motors can be divided into square wave DC motors (BLDCM) and sine wave DC motors (PMSM). BLDCM replaces the mechanical commutation of the original DC motor with electronic commutation. The permanent magnet material is used as the rotor, eliminating the need for brushes; while PMSM replaces the field winding in the synchronous motor rotor with permanent magnet material, eliminating the need for field windings, slip rings and brushes. Under the same conditions, it is easier for the drive circuit to obtain a square wave, and the control is simple, so the application of BLDCM is much wider than that of PMSM.

Brushless DC motors are generally composed of three parts: electronic commutation circuit, rotor position detection circuit and motor body. Electronic commutation circuit is generally composed of control part and driving part, and the detection of rotor position is generally completed by position sensor. When working, the controller triggers each power tube in the drive circuit in an orderly manner according to the position of the motor rotor measured by the position sensor, and performs orderly commutation to drive the DC motor.