The working principle of brushless DC motor

Update:29 Mar 2021
Summary:

The stator of a brushless DC motor is a coil winding ar […]

The stator of a brushless DC motor is a coil winding armature, and the rotor is a permanent magnet. If only a fixed DC current is applied to the motor, the motor can only generate a constant magnetic field, and the motor cannot rotate. Only the position of the motor rotor is detected in real time, and then the different phases of the motor are connected with corresponding currents according to the position of the rotor. The stator generates a rotating magnetic field with uniform changes in direction, so that the motor can rotate with the magnetic field.

Figure 2 shows the schematic diagram of the rotation principle of the brushless DC motor. For the convenience of description, the center tap of the motor stator coil is connected to the motor power supply POWER, the end points of each phase are connected to the power tube, and the G pole of the power tube is connected when the position sensor is turned on. 12V, the power tube is turned on, and the corresponding phase coil is energized. As the three position sensors turn on in turn with the rotation of the rotor, the corresponding phase coils are also energized in turn, so that the direction of the magnetic field generated by the stator changes continuously, and the motor rotor also rotates. This is the brushless DC motor. The basic principle of rotation-detecting the position of the rotor, energizing each phase in turn, so that the direction of the magnetic field generated by the stator changes continuously and uniformly.

Three driving methods of brushless DC motor

The driving mode of brushless straight machine motor can be divided into a variety of driving modes according to different categories, and they have their own characteristics.

According to drive waveform:

Square wave drive, this drive mode is convenient to implement and easy to realize the position sensorless control of the motor;

Sinusoidal drive, this drive mode can improve the motor running effect and make the output torque uniform, but the realization process is relatively complicated. At the same time, this method has two methods, SPWM and SVPWM (Space Vector PWM). The effect of SVPWM is better than SPWM.

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