Is it possible to omit the frequency converter in the constant pressure water supply system? What is the use of the inverter in the constant pressure water supply system? (2)

4. Control method of variable frequency and constant pressure water supply

The function of the frequency converter is to provide a variable frequency power supply for the motor to realize the stepless speed regulation of the motor, so that the water pressure of the pipe network changes continuously. The task of the sensor is to detect the water pressure of the pipe network, and the pressure setting unit provides the system with the expected value of the water pressure that meets the needs of the user. After the pressure setting signal and pressure feedback signal are input to the programmable controller, they are calculated by the internal PID control program of the programmable controller and output to the frequency converter a speed control signal. Another method is to send the pressure setting signal and the pressure feedback signal to the PID loop regulator. After the PID loop regulator performs calculations inside the regulator, it outputs a speed adjustment signal to the inverter.

5. The composition of variable frequency constant pressure water supply

The variable frequency constant pressure water supply system is mainly composed of a pool, a variable frequency control cabinet, a pressure sensor, a centrifugal pump, and a touch screen display. The frequency conversion control cabinet is composed of circuit breakers, frequency converters, contactors, intermediate relays, and PLCs.
Principles for selection of water supply system
(1). The storage tank capacity should be greater than the maximum water supply per hour.
(2). The pump lift should be greater than the actual water supply height.
(3). The sum of the pump flow rates should be greater than the actual maximum water supply.
(4). Frequency conversion control cabinet selection:
The model and number of pumps can be determined according to the water supply volume and water supply height, and then the control cabinet can be selected.

6. Conclusion

6.1 Features of variable frequency and constant pressure water supply system:

  1. Fully automatic, unmanned operation
    The variable frequency and constant pressure water supply system will automatically adjust the pump speed according to the user’s water consumption, determine the number of pumps to add or subtract, and the working procedures of fire inspection, etc., without manual intervention and manual operation.
  2. Less investment in infrastructure construction, no pollution to water sources, and no need for antifreeze treatment
    The system equipment is compact, saving construction area by 60~70%, and saving construction funds (relative to water tower) can reach 80~90%. Because the constant pressure water supply directly sends the source water to the end user, there is no water storage link in the middle, which solves the problem of secondary pollution in the water supply of water towers and water tanks, and there is no need to do antifreeze treatment like high water tanks in severe cold winter.
  3. Water and electricity saving effect is obvious
    If the water supply system does not use frequency conversion control, the water pump can only run continuously under the drive of the industrial frequency power supply. When the pressure in the water consumption drop pipe rises, the excess pressure can only be released through the pressure relief valve, which causes a lot of energy waste. After adopting frequency conversion control, the pressure in the pipe can be controlled by adjusting the speed of the water pump, thus achieving the purpose of energy saving.
    This system can save water up to 15~25%; due to the frequency conversion speed control, the motor and water pump always work in the high-efficiency area, and a series of energy-saving measures taken by the system can make the energy saving rate of the entire water supply system as high as 20~50% .
  4. Perfect protection function to realize uninterrupted water supply
    The system is designed with full consideration of the performance of submersible electric pumps, inverters, etc. It has a variety of protection functions such as phase loss, undervoltage, overvoltage, overcurrent, overheating, overload, unbalance, motor thrust wear, and lack of protection. Various protection functions such as water, and the system’s fault self-diagnosis function facilitates users to troubleshoot faults. The automatic dialing function of the fault phone truly realizes the unattended operation of the pump room. The system also has three types of manual, semi-automatic and fully automatic The working method ensures the continuity of water supply.
  5. Easy to debug and maintain, and the display is intuitive and clear
    The system adopts the latest IPM module frequency converter and intelligent programmable controller, and uses advanced technologies such as fuzzy pressure control to make system debugging, maintenance and repair simple and convenient.
    The system voltage, current, feedback pressure, inverter output frequency, current, motor speed and other operating parameters are directly displayed on the cabinet panel, which is intuitive and easy to maintain.
  6. Flexible settings and complete functions
    The system functions can be flexibly configured through PLC programming design, and various special functions such as regular inspection, daily and weekly timing switch, multi-pressure setting, variable pressure water supply, etc. can be added to meet the special requirements of different users.
    It can be connected to the upper computer of various interfaces to realize the remote monitoring of the system by the computer.
    At the same time, other closed-loop control systems can be formed according to user needs, such as constant liquid level, constant flow, proportional control and other control systems.

6.2 Application of variable frequency and constant pressure water supply system:

  1. Various types of tap water systems, constant pressure water supply systems with submersible electric pumps for wells.
  2. Domestic water for high-rise buildings and residential communities;
  3. Water for industrial and mining enterprises, water supply systems that require constant pressure variables for the production process, such as circulating cooling water, air-conditioning refrigeration, stabilized water supply for boiler heating systems, and circulating water for swimming pools;
  4. Oil field pipelines, oil depots, pumping stations, oil port constant pressure oil delivery systems and other fluid delivery systems;
  5. Rural tap water, agricultural irrigation and drainage and construction water, garden spraying, water features and music fountain systems.
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