The Application of AC Drive in water pumps

• 2025 Jul 21

The frequency converter, also known as variable frequency drive(VFD) is widely used in water pump area. It is used as an energy-saving water supply device that controls the rotational speed of the water pump motor by adjusting the power supply frequency. It is widely applied in fields such as residential water supply, industrial constant pressure water supply, central air conditioning systems and farmland    irrigation. The core function is to precisely regulate the flow and pressure of the water pump by   changing the motor speed, forming a closed-loop control system.

Energy conservation and consumption reduction

The shaft power of the water pump is directly proportional to the cube of the rotational speed of the water pump. So the shaft power of the water pump can be changed by altering its rotational speed. The variable frequency drive adjusts the motor speed to match the actual demand, avoiding energy waste caused by valve throttling. For instance, When the water demand decreases, variable frequency drive can reduce the rotational speed to avoid motor idling losses.

Precise flow control

The frequency is adjusted by a frequency converter to achieve stepless speed regulation from 0 to 100%. When combined with a pressure sensor, a closed-loop control can be formed. Precisely match the actual amount of  flow/pressure demand. In a constant pressure water supply system, the frequency converter can adjust the rotational speed in real time to maintain pressure fluctuations within ±0.01MPa. 

Soft start protection

The Variable frequency drive can controls the motor to start slowly. Compare with the traditional direct start，the starting current can reach 6 to 7 times the rated current. The starting current is only 1.2 to 1.5 times the rated current. Reduce mechanical shock and frequent start-stop wear of mechanical components (such as valves), thus can extend the service life of water pump bearings and seals by approximately 20% to 30%.

Eliminate the water hammer effect

Due to the water hammer effect, the maximum water pressure can reach up to four times the normal pressure. The variable frequency drive controls the start and stop speed of the water pump to prevent water hammer caused by sudden pressure changes. 

Typical application scenarios and cases

Building water supply system, the high-rise residential buildings adopt a "one-to-many" frequency conversion solution, where a single frequency converter controls multiple water pumps, achieving an energy-saving rate of over 40%. In Industrial circulating water system, the Chemical enterprises achieve dynamic regulation of cooling water flow through PID closed-loop control, saving 35% of pump energy consumption. It also used in Agricultural irrigation area, The frequency converter, in combination with the pressure sensor, adapts to the demands of different irrigation areas, saving more than 15% of water. In Fire hydrants and automatic sprinkler systems, Through the linkage of the air pressure tank and the automatic control system, the pressure and water level inside the tank are adjusted in real time to ensure the water storage capacity for fire protection. By Automatic air replenishment it can achieve pressure stabilization. In the central air conditioning system, in the variable frequency control system of central air conditioning, the fan is precisely controlled through temperature closed-loop control to achieve stable temperature regulation. In addition, the cooling water system also adopts variable frequency control, which can adjust the cooling water flow in real time according to the outlet water temperature, thereby ensuring the cooling effect while achieving energy conservation and efficiency improvement.

Future development trend of frequency converters

The new generation of frequency converters is equipped with built-in AI algorithms, which can predict the wear of the water pump, So an alarm can be triggered when the vibration value is greater than the set value. In the photovoltaic water pump system, the inverter achieves a DC/AC conversion efficiency of 98%,Through the rational application of frequency converters, photovoltaic water pump system can not only significantly reduce energy consumption, but also improve control accuracy and reliability。So in the future, the variable frequemcy drive will be more intelligent integrated and more adapted to the new energy industry.