1 Introduction
Traditional water supply solutions not only have high initial investment costs, but also high maintenance costs and labor inputs in the later stages. In addition, the water supply pressure is unstable, the power consumption is high, and the waste of water resources is also quite serious.
With the continuous development of society and the enormous consumption of natural resources by humankind, energy conservation and water saving have become urgent social needs. Therefore, a new water supply solution is imperative. In recent years, constant pressure water supply solutions achieved through frequency converters have effectively solved the problems brought about by traditional water supply solutions. It is believed that this solution will become the development trend of the water supply industry.
2. Traditional water supply system
1. Water supply system with a single constant speed pump
Water supply method: The water pump directly inputs water from the reservoir into the water supply network, and the water pump runs at a constant speed from the start of water supply to the stop of water supply.
Advantages: The system is simple and inexpensive;
Disadvantages: Unstable pipeline pressure, high energy consumption, and significant water waste.
2. Water supply system with constant speed pump and water tower
Water supply method: Water is pumped into the water tower, and then the water tower supplies water to the pipe network. The water pump starts working when the water level in the water tower is lower than a certain level, and stops working when the water level is lower than a certain level.
Advantages: Compared to the previous water supply method, the water supply pressure is more constant and the energy consumption is relatively small;
Disadvantages: large investment in equipment, large footprint, non-adjustable water pressure, and frequent pump start-stop causing significant equipment wear and tear.
3. Water supply system with constant speed pump and pressure tank
Water supply method: Water is pumped into the pressure tank by a water pump, and then the pressure tank supplies water to the pipe network. The water pump starts working when the pressure in the pressure tank is lower than a certain pressure, and stops working when the pressure in the pressure tank is higher than a certain pressure.
Advantages: Lower cost compared to water towers;
Disadvantages: Frequent start-stop of the water pump causes significant equipment wear and tear and high energy consumption.
3 HD31 Technical Features
The HD31 frequency converter utilizes an advanced customized design concept, focusing on the needs of the water supply industry. It perfectly combines advanced motor control technology with constant pressure water supply control logic. With rich water supply control logic functions, strong overload capacity, and comprehensive fault protection, it can meet the energy-saving renovation and application requirements of various water supply systems.
3.1 Abundant water supply control logic functions
(1) Two water supply modes
The constant pressure water supply debugging mode is mainly used to test the wiring of motors and the wiring of inverter output terminals;
The constant pressure water supply operation mode is the mode that must be selected when the constant pressure water supply is in operation.
(2) Water level detection function
The water level detection includes three modes: no water level signal detection, input via digital input terminal, and input via analog input terminal. The water level detection function primarily monitors the water level in the reservoir and implements different water supply measures based on different conditions. When the water level drops, the system operates at the standby pressure when it reaches the lower limit; if the water level drops to the water shortage level, the system will shut down all currently running pumps. When the water level rises, the system restarts the pumps and begins supplying water at the standby pressure when it reaches the lower limit; only when the water level rises to the upper limit will the system supply water at the normal pressure.
(3) Pump rotation function
The pump rotation function is designed to address the issue of some pumps being shut down for extended periods and rusting when the water supply system maintains a stable water pressure.
(4) Hibernation function
The hibernation function occurs when the current water supply system detects that the water supply network pressure is consistently higher than the expected set pressure. At this time, the variable frequency water pump is still in the lower limit frequency and will be in a zero frequency output state. If hibernation is performed at this time, energy will be saved. When the network pressure drops, the system will be reawakened to continue supplying water.
(5) Set water supply pressure for multiple time periods
Multi-time-period pressure water supply is suitable for residential water supply, where water consumption varies significantly at different times.
(6) PID function
For the set pressure signal input to the water supply system and the feedback pipeline pressure signal, the PID control characteristic is used to make the pipeline pressure of the system eventually tend to the set pressure.
3.2 Superior overload capacity
- Rated output current for 2 minutes;
- Rated output current 10 seconds;
3.3 Comprehensive fault protection
4. Constant Pressure Water Supply Application Cases
4.1 Site conditions and wiring
The system utilizes three asynchronous motors, a remote pressure gauge with a DC 0-10V range and a 1MPa range, a potentiometer with a 0-10V range, and a level sensor. The potentiometer signal sets the desired pipeline pressure, the remote pressure gauge signal feeds back to the HD31 to monitor the actual pipeline pressure, and the level sensor monitors the current water level in the reservoir. The HD31 uses the information from the level sensor to determine whether the system should continue pumping water from the reservoir. When the reservoir is full, the HD31 uses its built-in PID function to calculate the desired pipeline pressure based on the potentiometer and remote pressure gauge signals. The wiring diagram is shown in Figure 1.
4.2 Debugging Process
(1) Wiring should be done according to Figure 1 above;
(2) Enable water supply expansion function and enable water supply expansion card;
(3) Set the rated current of water pump 1 according to the motor nameplate;
(4) Set the command given channel;
(5) Set acceleration/deceleration time, analog quantity function, and terminal function;
(6) Adjust the two analog signals and adjust the PID parameters according to the actual performance.
4.3 Parameter Settings
Functional parameters | Parameter Description | Setting values and descriptions |
|---|---|---|
F00.04 | Universal expansion card selection | 2 (Select water supply card) |
F00.05 | Extended application functionality | 1 (Enable water supply function) |
F00.11 | Command to set channel | 1 (Terminal given command terminal) |
F15.00 | DI1 terminal function selection | 2 (Forward rotation command given) |
P00.00 | Water supply mode selection | 0 (Constant pressure water supply operation mode) |
P00.01 | Water level signal input selection | 1 (Input via digital input terminal) |
P00.17 | Hibernation function enabled | 1 (Enable hibernation function) |
P01.00 | Water pump type selection | 1 (Variable Frequency Pump) |
P01.01 | Water pump type 2 selection | 2 (Industrial frequency pump) |
P01.02 | Water pump type 3 selection | 2 (Industrial frequency pump) |
P03.00 | AI1 Function Selection | 1 (Simulated pressure setting) |
P03.01 | AI2 Function Selection | 2 (Simulation Feedback Settings) |
P03.05 | DI2 Function Selection | 15 (Upper limit water level of the inlet pool) |
P03.06 | DI3 Function Selection | 16 (Lower limit water level of the inlet pool) |
P03.07 | DI4 Function Selection | 17 (Water level in the inlet tank is low) |
P03.15 | RLY1 Output Function Selection | 1 (Water pump 1 frequency converter control) |
P03.16 | RLY2 Output Function Selection | 2 (Water pump 1 frequency control) |
P03.17 | RLY3 Output Function Selection | 4 (Water pump 2 frequency control) |
P03.18 | RLY4 Output Function Selection | 6 (Water pump 3 frequency control) |
P03.19 | RLY5 Output Function Selection | 15 (Hibernation Operation Instruction) |
P03.20 | RLY6 Output Function Selection | 19 (Water shortage indicator in the reservoir) |
P03.21 | RLY7 Output Function Selection | 23 (Indication that the water supply system is in operation) |
After setting the desired network pressure, the constant pressure water supply system is started. Through the PID function built into the HD31, water pump 1 quickly adjusts from 0Hz to the upper limit frequency of the PID. At this time, the desired network pressure has not yet been reached. After the pump detection time is exceeded, the frequency converter immediately reduces from the upper and lower limits of the PID to the lower limit frequency according to the preset deceleration time. At the same time, water pump 2 is put into use in power frequency mode. Then water pump 1 runs again according to the frequency adjusted by the PID. At this time, the signal fed back from the remote pressure gauge is basically stable within the range of our preset network pressure.
5. Conclusion
Multiple pressure setting modes meet various engineering implementation needs; advanced PID regulation ensures stable pipeline pressure; water level control ensures water supply is suspended when the reservoir water level is insufficient, saving energy and reducing mechanical wear; and sleep control ensures all water pumps are shut down when pipeline pressure is continuously too high, achieving energy savings. Practical use shows that the HD31 effectively achieves constant pressure water supply. Its superior motor performance, rich control functions, and stable and reliable performance have ultimately won customer recognition. The HD31 will continue to make its due contribution to energy conservation and emission reduction in the water supply industry.
