Principle of Brushless DC Motor
Apr 23, 2019
This paper will introduce the development of Brushless DC motor which is fast and widely used in motor types. Brushless DC motor is widely used in daily life appliances, automotive industry, aviation, consumer electronics, medical electronics, industrial automation and other devices and instruments. As the name implies, brushless DC motor directly uses electronic commutator instead of mechanical commutator brush. Compared with brushless DC motor, brushless DC motor has many advantages, such as:
  • Better torque speed characteristics.
  • High speed dynamic response;
  • High efficiency;
  • Long life;
  • Low noise;
  • High speed.
In addition, BLDCM has better torque and shape-size ratio, which makes it more suitable for the occasion which is sensitive to the weight and size of the motor itself. In this application note, the structure, basic principles, characteristics and applications of BLDCM will be discussed in a series of ways. The terminology that may be used in the process can be found in Appendix B "glossary".

1.brushless DC motor structure and basic working principle

  • Brushless DC motor is a kind of synchronous motor, which means that the magnetic field produced by its stator and rotor is the same frequency, so the brushless DC motor will not produce the frequency difference phenomenon of ordinary induction motor. Brushless DC motor also has single phase and 2 phases.

  • The difference between 3 phase motors determines the number of stator winding windings. Here we will focus on the most widely used 3 phase brushless DC motor.

2. stator

  • The stator of brushless DC motor is made of many silicon steel sheets by overlapping and axial stamping. There are certain coils in each punching slot. Traditionally, the stator of brushless DC motor is similar to the stator of induction motor, but there are some differences in the distribution of stator windings. Most brushless DC motors have three windings arranged in a row of stars. Each winding is composed of a number of internally bonded steel sheets in a certain way. Even number of windings are distributed around the stator to form even number of poles.

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