Compared with AC induction motor, brushless DC motor has the following advantages:

1. rotor adopts magnets without exciting current. The same electrical power can achieve greater mechanical power.

2. the rotor has no copper loss and iron loss, and the temperature rise is even smaller.

3. the starting and blocking moment is large, which is beneficial to the instantaneous torque required for valve opening and closing.

4. the output torque of the motor is directly proportional to the working voltage and current. The torque detection circuit is simple and reliable.

5. by adjusting the average value of the supply voltage through PWM, the motor can be adjusted smoothly. The speed regulating and driving power circuit is simple and reliable, and the cost is low.

6. by lowering the supply voltage and starting the motor by PWM, the starting current can be reduced effectively.

7. motor power supply is PWM modulated DC voltage. Compared with the sine wave AC power supply of AC variable frequency motor, its speed regulation and drive circuit produce less electromagnetic radiation and less harmonic pollution to the grid.

8. using closed loop speed control circuit, the motor speed can be changed when load torque changes.