The speed of the motor is determined, which is related to the speed of the pump and the transmission mode, such as the direct drive, the speed of the two should be equal, such as indirect transmission, both of the rated speed has a certain speed ratio relationship.
The AC motor speed and power frequency (alternatingcurrentfrequency) magnetic pole pairs F, motor (numberofpolepair) and P (Slipratio) s slip, due to f and s with little change, so the motor speed depends on the motor poles P. In the choice of motor, not only to meet the requirements of power, but also should try to make the motor speed and pump consistent, in order to improve the transmission efficiency and reduce transmission equipment investment. It should be pointed out that the same capacity of the motor, rated speed is higher, the smaller the size, high efficiency, high power factor, but also the more economical. Therefore, the speed is very low for large pumps, if the use of direct drive, you need to choose a large number of poles of the motor, so that the volume of the motor and increase investment, but not the economy. At this time, can choose a higher speed of the motor, increase the transmission equipment to reduce the speed of the pump to ensure the needs of speed.
