Three control methods for brushless motors
Time:2023-12-17
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There are three control methods for brushless motors: square wave control, sine wave control, and FOC control; When adjusting the current and voltage of the controller, attention should be paid to adjusting the length of constantan and adjusting the resistance of the power supply connection. Below is a specific introduction to the control method and basic maintenance of brushless motors
Control method of brushless motor
1. Square wave control
Square wave control uses Hall sensors or sensorless estimation algorithms to obtain the position of the motor rotor, and then performs 6 commutations (every 60 ° commutation) within a 360 ° electrical cycle based on the rotor position. Each reversing position motor outputs a specific direction of force, so it can be said that the position accuracy of square wave control is electrical 60 °. Due to this control method, the phase current waveform of the motor is close to a square wave, so it is called square wave control. The advantage is that the control algorithm is simple, the hardware cost is low, and using a controller with ordinary performance can achieve a higher motor speed; The disadvantages are large torque fluctuations, certain current noise, and insufficient efficiency. Square wave control is suitable for situations where the rotational performance of the motor is not highly required.
2. Sine wave control
The sine wave control method uses SVPWM waves to output a 3-phase sine wave voltage, and the corresponding current is also a sine wave current. This method does not have the concept of square wave control commutation, or assumes that an infinite number of commutations have been carried out within an electrical cycle. Obviously, compared to square wave control, sine wave control has smaller torque fluctuations, fewer current harmonics, and feels more delicate to control. However, it requires slightly higher performance from the controller than square wave control, and the motor efficiency cannot be maximized.
3. FOC control
Sine wave control realizes the control of voltage vector and indirectly controls the magnitude of current, but cannot control the direction of current. The FOC control method can be considered as an upgraded version of sine wave control, which realizes the control of current vector, that is, the vector control of motor stator magnetic field.
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