How VFD improves the operational stability of constant pressure boosting systems

In the field of modern industrial production and urban water supply, the stable operation of constant pressure boosting systems is directly related to production efficiency and quality of life. As the core component of the constant pressure boosting system, the variable frequency drive (VFD) provides a solid guarantee for the stability of system operation from multiple dimensions with its advanced technical characteristics. ​
1. Soft start and soft stop: eliminate shock and extend equipment life

In traditional water supply systems, when the water pump adopts direct start mode, the instantaneous current at start-up can reach 5-7 times the rated current. Such a huge current shock will not only cause serious fluctuations in the power grid, but also cause great mechanical stress on components such as the water pump motor, bearings, and couplings. The heat generated by the motor winding under high current will accelerate the aging of the insulation, and the bearings and couplings will wear and loosen due to the instantaneous mechanical shock, greatly shortening the service life of the equipment. ​
The VFD Controlled Constant Pressure Booster System adopts soft start technology to gradually increase the output voltage and frequency to steadily increase the speed of the water pump motor. During the startup process, the starting current can be effectively controlled within 1.5-2 times of the rated current. This process avoids the impact on the power grid and reduces the impact of voltage sag on other electrical equipment; at the same time, the gentle startup process also reduces the stress on mechanical parts and greatly reduces equipment wear. ​
Soft stop is also of great significance to system stability. In the traditional emergency stop mode, the water pump suddenly stops rotating, and the water flow will have a strong impact on the water pump and the pipe network due to inertia, which is easy to cause water hammer. The instantaneous high pressure generated by water hammer can reach several times or even dozens of times the normal pressure, which may cause pipe rupture and loose joints, seriously threatening the safety of the water supply system. The soft stop achieved by VFD gradually reduces the output frequency and voltage, so that the speed of the water pump gradually decreases, and the water flow speed also decreases steadily, effectively avoiding the occurrence of water hammer and protecting the integrity of the entire water supply system. ​
2. Accurate speed control: dynamic adjustment, stable water pressure ​
The precise control of the speed of the water pump by VFD is the core of ensuring the stability of the water pressure in the pipe network. As the sensing element of the system, the pressure sensor monitors the water pressure of the pipe network in real time and feeds the data back to the control system in the form of electrical signals. The control system compares and analyzes the pressure signal with the preset target pressure value. Once it detects that the actual water pressure deviates from the set value, it immediately sends an adjustment command to the VFD. ​
After receiving the command, the VFD can adjust the output frequency in a very short time. According to the positive proportional relationship between the motor speed and the power supply frequency, the speed of the water pump motor will change accordingly, and then adjust the water output and water pressure of the water pump. When the water pressure drops due to the increase in water consumption, the VFD increases the output frequency, the speed of the water pump motor increases, the water output increases, and the water pressure of the pipe network rises; conversely, when the water consumption decreases and the water pressure increases, the VFD reduces the output frequency, the speed of the water pump motor slows down, the water output decreases, and the water pressure falls back to the set value. ​
This dynamic adjustment mechanism can adapt to various complex changes in water use conditions. Whether it is the intermittent water use of equipment in industrial production or the fluctuation of water use during the morning and evening peaks in urban life, the VFD can respond quickly and control the water pressure of the pipe network within a very small fluctuation range. Through precise speed control, the system can prevent excessive water pressure from damaging the pipe network, and prevent low water pressure from affecting normal water use, providing a stable and reliable water pressure environment for various water-using equipment. ​
III. Perfect protection mechanism: resist risks and ensure safety​
The various protection mechanisms built into the VFD constitute a safety barrier for the operation of the system. Overcurrent protection is an important part of it. When the current of the pump motor exceeds the set threshold due to excessive load, mechanical failure or pipe blockage, the VFD will quickly cut off the power supply. This protection action can be completed within tens of milliseconds, effectively preventing the motor from burning due to long-term overcurrent and avoiding serious damage to the equipment. ​
Overvoltage protection and undervoltage protection are mainly aimed at abnormal power supply voltage. In some areas with unstable power supply, voltage fluctuations are frequent. When the power supply voltage exceeds the specified upper limit, the overvoltage protection is activated and the VFD stops working to prevent the motor insulation layer from being broken down; when the voltage is lower than the specified lower limit, the undervoltage protection is activated to prevent the motor from overloading due to insufficient torque and protect the motor and other equipment from damage. ​
Overheat protection monitors the temperature of the VFD and motor in real time. The temperature of the equipment may rise in the case of long-term continuous operation or poor heat dissipation conditions. When the temperature reaches the preset alarm value, the VFD will automatically reduce the operating frequency and reduce the heat generation; if the temperature continues to rise to a dangerous value, it will stop to dissipate heat and restart after the temperature returns to normal. The phase loss protection function can cut off the power supply in time when the power supply is phase-lost, avoiding abnormal vibration and overheating of the motor due to three-phase imbalance, and effectively protecting the normal operation of the motor. These protection mechanisms cooperate with each other, so that the system can take timely measures in the face of various abnormal conditions to ensure the safe and stable operation of the system. ​
Fourth, coordination with the control system: intelligent regulation and optimized operation​
The close coordination between VFD and the control system gives the constant pressure boosting system intelligent regulation capabilities. The preset control strategies and algorithms in the control system can automatically adjust the operating parameters of the VFD according to different water use scenarios and time patterns. In commercial office buildings, the water demand during working hours, lunch breaks and off-get off work hours on weekdays is significantly different. Based on historical water consumption data and real-time monitoring, the control system can adjust the VFD output frequency in advance before work to increase the pump speed and reserve enough water pressure to cope with the upcoming peak water consumption; during low water consumption periods such as lunch breaks and after get off work, the pump speed is reduced to reduce energy consumption while maintaining the necessary water pressure. ​
Through the communication interface, the VFD can realize real-time data interaction with the remote monitoring center. The staff can remotely view the operating parameters of the VFD, such as frequency, voltage, current, power, etc., and can also obtain the system's operating status information, including the start and stop status of the pump, fault alarm, etc. Once the system is abnormal, the remote monitoring center can promptly discover and diagnose the fault, adjust the VFD's operating parameters or issue a shutdown command through remote control to avoid the expansion of the fault. In the urban water supply system, multiple water supply stations realize the collaborative work between stations through this intelligent control and remote monitoring method. When a certain area causes a drop in local water pressure due to pipeline maintenance and other reasons, the system can automatically adjust the operating status of the pumps at surrounding stations to ensure the stability of the water pressure in the area, greatly improving the overall stability and emergency handling capabilities of the urban water supply system. ​
​