Three Speed Control Methods for Brushless Motors
Voltage control: Typically, a brushless motor is paired with a driver, and the motor's input voltage can be adjusted by changing the output voltage of the driver, thereby controlling the motor's speed.
PWM control: PWM (Pulse Width Modulation) control involves modulating a constant DC voltage into a pulse voltage sequence with a fixed frequency and adjustable pulse width. This allows for the adjustment of the average output voltage to regulate the motor's speed. In essence, it adjusts the duty cycle, which is the ratio of the high-level and low-level time in the pulse signal. For example, if the high-level voltage is 5V and the low-level voltage is 0V, a 50% duty cycle means equal high-level and low-level times, resulting in an analog output voltage of 2.5V at a certain frequency. With a 75% duty cycle, the voltage output would be 3.75V.
A higher duty cycle leads to a higher pulse magnitude, resulting in a higher voltage and faster speed. Conversely, a lower duty cycle reduces the speed. Therefore, when using PWM control, if the high-level voltage is 5V and a 3.3V magnitude is used, the motor will only run at 66% of its maximum speed. To achieve a higher speed, the maximum speed of the motor can be increased proportionally to the desired speed.
Series resistor control: This method involves connecting a potentiometer in series, but it is inefficient and suitable only for low-power motors. It is generally not recommended for high-power motors to use potentiometer speed control.
PWM control: PWM (Pulse Width Modulation) control involves modulating a constant DC voltage into a pulse voltage sequence with a fixed frequency and adjustable pulse width. This allows for the adjustment of the average output voltage to regulate the motor's speed. In essence, it adjusts the duty cycle, which is the ratio of the high-level and low-level time in the pulse signal. For example, if the high-level voltage is 5V and the low-level voltage is 0V, a 50% duty cycle means equal high-level and low-level times, resulting in an analog output voltage of 2.5V at a certain frequency. With a 75% duty cycle, the voltage output would be 3.75V.
A higher duty cycle leads to a higher pulse magnitude, resulting in a higher voltage and faster speed. Conversely, a lower duty cycle reduces the speed. Therefore, when using PWM control, if the high-level voltage is 5V and a 3.3V magnitude is used, the motor will only run at 66% of its maximum speed. To achieve a higher speed, the maximum speed of the motor can be increased proportionally to the desired speed.
Series resistor control: This method involves connecting a potentiometer in series, but it is inefficient and suitable only for low-power motors. It is generally not recommended for high-power motors to use potentiometer speed control.
Updated on: 13/03/2025
Thank you!