The principle of water pump starting with frequency converter

The energy saving of the frequency converter is mainly manifested in the application of fans and water pumps. In order to ensure the reliability of production, all kinds of buckle end belt production machinery are designed with power drive, leaving a certain amount of surplus. When the motor cannot run under full load, in addition to meeting the power drive requirements, the excess torque increases the consumption of active power and causes a waste of electrical energy. The traditional speed regulation method of fan and buckle end belt equipment is to adjust the air supply and water supply by adjusting the inlet or outlet baffle and valve opening. The input power is large, and a large amount of energy is consumed in the baffle and valve interception. In the process. When using variable frequency speed regulation, if the flow requirement is reduced, the requirement can be met by reducing the speed of the pump or fan.

According to fluid mechanics, P (power) = Q (flow) × H (pressure), the flow Q is proportional to the first power of the speed N, the pressure H is proportional to the square of the speed N, and the power P is proportional to the cube of the speed N If the efficiency of the water pump is constant, the speed N can be reduced proportionally when the required adjustment flow decreases, and the shaft output power P will decrease in a square relationship at this time. That is, the power consumption of the water pump motor and the rotation speed are approximately in a square ratio relationship. When the required flow rate Q decreases, the output frequency of the frequency converter can be adjusted to reduce the motor speed n proportionally. At this time, the power P of the motor will be greatly reduced according to the cubic relationship, which is 40%-50% more energy-saving than adjusting the baffle and valve, so as to achieve the purpose of saving electricity.

For example: a centrifugal pump motor power is 55 kilowatts, when the speed drops to 4/5 of the original speed, its power consumption is 28.16 kilowatts, saving 48.8% of electricity, when the speed drops to 1/2 of the original speed, its The power consumption is 6.875 kilowatts, which saves power by 87.5%.