Water pumps, as we all know, are power components used to transport liquids, and many sectors of the national economy rely on them. They come in a wide variety of types and specifications, and can be classified in different ways. Based on their working principle, they can be divided into three main categories: centrifugal pumps, positive displacement pumps, and other types of pumps.
ISG inline centrifugal pump
Currently, the main product on the market is the centrifugal pump, a type of vane pump, and also the most widely used pump type. This type of pump works by using the high-speed rotation of the impeller to cause the blades to rotate the liquid, giving the liquid centrifugal force to complete the water pumping process. Its applications cover various fields such as domestic hot water supply, sewage drainage, industrial applications, commercial building HVAC circulation, and cooling water transportation. Centrifugal pumps are important pieces of equipment, consuming a significant amount of power to operate! Statistics show that 20% of the world's electricity is consumed by pump systems. However, with necessary technical measures and control methods, 30%-50% of this energy consumption can be saved.
1. Constant speed pumps and variable speed pumps:
Traditional heating and air conditioning systems select circulating water pumps based on a single-mode regulation operation. The selection principle is that the pump flow rate cannot be less than the required flow rate of the external network, generally 1.1 to 1.2 times the theoretical flow rate of the external network . The head is selected based on 1.05 to 1.10 times the total resistance of the pipeline and the user. At this point, the corresponding shaft power is already greater than 100%. It can be seen that the power consumption of the water pump is very high when operating in a constant flow mode. However, the regulation effect is very ideal.
When a water pump operates under a constant flow rate, the required flow rate of the system decreases under partial load. To adapt to the change in flow rate, the valve opening needs to be reduced to change the system characteristic curve, which consumes excess pressure head and wastes a lot of electrical energy!
We can adjust the pump's operating point by changing the valve opening; another method is to change the pump speed.
As can be seen, when the pump speed changes, the pump performance curve will change simultaneously, and the speed will change with the frequency [Hz]. Performance analysis of the circulating water pump shows that the pump flow rate, head, and shaft power all have a certain proportional relationship with the pump impeller speed.
As can be seen, the pump head is directly proportional to the square of the motor speed, and the pump shaft power is directly proportional to the cube of the motor speed. That is, when the pump flow rate decreases by 20%, the motor speed should decrease by 20%, resulting in a 50% reduction in pump power consumption; when the pump flow rate decreases by 50%, the motor speed should decrease by 50%, resulting in an 87.5 % reduction in pump power consumption. When the system requires a reduced flow rate, reducing the motor speed correspondingly reduces the pump flow rate and pump shaft power, resulting in significant energy savings. Furthermore, the use of variable speed control avoids unnecessary valve head losses associated with valve regulation.
II. Speed Control Principle:
When the flow rate decreases, the controller detects a pressure signal (sensor motor current or speed status). At this time, the controller sends a signal to the inverter, causing it to reduce its output (lower frequency) until the pressure returns to the required level (setpoint). Conversely, when the flow rate increases again, the controller detects a pressure decrease. The controller sends a signal to the inverter, causing it to increase its output (higher frequency) until the pressure returns to the required level (setpoint).
3: Overall efficiency of the variable speed pump
The pump efficiency commonly referred to is only the pump efficiency [hp] , but strictly speaking, we should measure its total efficiency:
Overall efficiency [ht] assessment must consider motor efficiency [hm], pump efficiency [hp], and conversion efficiency [hd] simultaneously. Overall efficiency refers to the change from P1 to P4. Motor efficiency varies depending on the motor efficiency class and the motor load.
Variable frequency technology will be increasingly recognized and applied. With proper system design (such as a tertiary pump system) and scientific pump selection and matching, users will experience greater comfort and energy savings.
