Working principle and structure analysis of brushless motor

Brushless DC motor is the use of semiconductor switching devices to achieve electronic commutation, that is, electronic switching devices instead of traditional contact commutator and brush. It has the advantages of high reliability, no reversing spark, low mechanical noise, and is widely used in high-grade recording booth, video recorder, electronic instrument and automatic office equipment.

Brushless DC motor is composed of permanent magnet rotor, multipole winding stator, position sensor and so on. Position sensing according to the change of rotor position, along a certain sequence of stator winding current converter (i.e. detecting the rotor magnetic pole relative to the position of the stator winding, and in determining the location of position sensor signal, the signal conversion circuit to control the power switch circuit, after processing according to certain logic relation between winding current switch). The operating voltage of the stator windings is provided by an electronic switching circuit controlled by the output of the position sensor.

There are three types of position sensors: magneto-sensitive, photoelectric and electromagnetic.

Brushless DC motor with magnetic-sensitive position sensor, its magnetic-sensitive sensor (such as Hall element, magnetic-sensitive diode, magnetic-sensitive polar tube, magnetic-sensitive resistor or special-purpose integrated circuit, etc.) is mounted on the stator assembly, which is used to detect the magnetic field changes caused by permanent magnet and rotor rotation.

The brushless DC motor with photoelectric position sensor is equipped with photoelectric sensor in a certain position on the stator component, and the light source is light-emitting diode or small bulb. When the rotor rotates, the light-sensitive components on the stator will generate pulse signals intermittently at a certain frequency due to the effect of the mask.

Using electromagnetic position sensor brushless dc motor, is in the electromagnetic sensors are installed on the stator component parts (such as the coupling transformer, close to switch, LC resonance circuit, etc.), when the permanent magnet rotor position changes, electromagnetic effect will make the electromagnetic sensor produces high frequency modulation signal (the amplitude changes with the rotor position).

In terms of structure, brushless motor and brush motor have similarities, also have rotor and stator, but brush motor and the structure of the opposite; The rotor of brush motor is the coil winding, and the power output shaft is connected, the stator is permanent magnet steel; The rotor of the Brushless motor is a permanent magnetic steel connected to the output shaft together with the shell, and the stator is a winding coil. It is called Brushless motor because the commutation brush used by the Brushless motor to convert the electromagnetic field alternately is removed. Then the problem is how to make the Brushless motor rotate without the conversion of electromagnetic field.

Rely on, in short, change the input to the brushless motor stator coil of alternating current wave frequency and waveform, the winding coil around a rotating magnetic field, electrical geometry axis on the magnetic field to drive the rotor permanent magnet steel, motor turned up and the performance of the motor and the number of magnetic steel, magnetic steel, magnetic flux intensity factors such as input voltage, the motor size, It also has a great relationship with the control performance of the brushless motor, because the input is direct current, and the current needs to be changed into 3-phase AC by the electronic governor, and the control signal needs to be received from the remote control receiver to control the speed of the motor, so as to meet the needs of the model. In general, the structure of the brushless motor is relatively simple, and the real decision of its performance is the brushless electronic governor. A good electronic governor needs the overall control of SCM control program design, circuit design, complex processing technology and other processes, so the price is much higher than that of the brush motor.