The meaning of brushless DC motor

The brushless DC motor has the same working principle and application characteristics as the general DC motor, but its composition is different. In addition to the motor itself, the former also has an additional commutation circuit, and the motor itself and the commutation circuit are closely integrated. The motor itself of many low-power motors is integrated with the commutation circuit. From the appearance, the DC brushless motor is exactly the same as the DC motor.

The motor itself of the brushless DC motor is the electromechanical energy conversion part. In addition to the two parts of the motor armature and the permanent magnet excitation, the brushless DC motor also has sensors. The motor itself is the core of the brushless DC motor. The brushless DC motor is not only related to performance indicators, noise and vibration, reliability and service life, but also involves manufacturing costs and product costs. Due to the use of permanent magnet magnetic field, the brushless DC motor can get rid of the traditional design and structure of the general DC motor, and meet the requirements of various application markets. The development of permanent magnet magnetic field is closely related to the application of permanent magnet materials. The application of the third-generation permanent magnet materials promotes brushless DC motors to move towards high efficiency, miniaturization and energy saving.

In order to achieve electronic commutation, the brushless DC motor must have a position signal to control the circuit. In the early days, the electromechanical position sensor was used to obtain the position signal, and now the electronic position sensor or its DC brushless motor method is gradually used to obtain the position signal. The easiest method is to use the potential signal of the armature winding as the position signal. The brushless DC motor must have a speed signal to realize the control of the motor speed. The speed signal is obtained by a similar method of obtaining the position signal. The simplest speed sensor is a combination of a frequency-measuring tachogenerator and an electronic circuit. The commutation circuit of the brushless DC motor consists of two parts, the driving part and the control part. The two parts are not easy to separate. Especially for low-power circuits, the two parts are often integrated into a single application-specific integrated circuit.

In the brushless DC motor, the drive circuit and the control circuit can be integrated into one of the motors with higher power. The drive circuit outputs electric power, drives the armature winding of the motor, and is controlled by the control circuit. At present, the DC brushless motor drive circuit has been transformed from a linear amplification state to a pulse width modulation switching state, and the corresponding circuit composition has also been transformed from a transistor discrete circuit to a modular integrated circuit. Modular integrated circuits are composed of power bipolar transistors, power field effect transistors and isolated gate field effect bipolar transistors. Although the isolation gate field effect bipolar transistor is more expensive, it is more appropriate to choose a DC brushless motor from the perspective of reliability, safety and performance.