Brushless dc motor control and speed regulation method

Dc brushless motor structure is reasonable, its speed is basically more stable, so in general, rarely to large speed regulation.Because the motor has a wide range of applications and can be used by many machines, it is necessary to adjust its speed according to different occasions.But the brushless dc motor control and speed regulation method needs everyone to learn, in order to faster application:

1. By controlling the order in which the coil is energized, the opposing coil is divided into a group and the current is energized to generate a magnetic field in the same direction.

2. The number of poles of brushless dc motor is three, so that each pair of “magnetic poles” can be conducted in a certain order to achieve the effect of magnetic field rotation.Under the action of magnetic field, the rotor of permanent magnet in the middle always has a tendency to keep the magnetic field in the same direction and will rotate with the rotating magnetic field.

H1H2H3 is three Hall sensors placed in the air gap of the excitation coil, which is used as an element to detect the magnetic field. The voltage can be changed according to the direction of the magnetic field, and the output is digital signal.

3. The stator coil is energized according to the next sequence, and the rotor magnetic field and stator magnetic field must have an Angle.There is no need to judge whether the brushless dc motor is just started, just need to execute the next command according to the working state sent back by the Hall sensor.

Its command is to send three pairs of coil on and off, these switches are achieved through the transistor.

The rotation of three-phase BLDC can be realized by energizing or cutting off three pairs of transistors in a certain order.

4. As the rotor rotates, the induced potential of each coil goes from the highest to zero and back again.Because when the coil is energized in the opposite direction, the reverse electromotive force will obstruct the reverse voltage, so the trapezoidal wave part will appear.The positive and negative voltage of the trapezoidal part of the zero is opposite, so the working state of the motor stator can be determined by detecting the positive and negative voltage after the voltage comparator.

Since the zero point is at the midpoint of the trapezoid, the rotation of the BLDC can be controlled after the control signal of corresponding time sequence is output after a delay of 30°.This control mode does not require Hall sensor, and three wires can drive the BLDC.If the waveform is relatively ideal, the three coil voltage curves can be obtained by directly integrating the voltage.So the brushless dc motor can be controlled.

5. Determine a starting direction, energize the lower coil in that direction first, make the rotor turn to the starting position in a short time, and energize the motor according to the following sequence of actions.

In order to improve the use efficiency of brushless dc motor, we need to learn to according to different use environment, different control and speed regulation, improve the use efficiency of the motor, control and speed regulation method can be applied to adjust the speed.

Post time: Mar-28-2020