Application of Oulun Frequency Converter in Constant Pressure Water Supply

   With the improvement of people's quality of life, the quality requirements for domestic water use are also getting higher and higher. At the same time, due to the requirements of the factory process, the quality of water supply has also drawn higher requirements. Frequency conversion constant pressure water supply is more and more recognized in the water supply industry for its advantages of environmental protection, energy saving and high quality of water supply. In the development of urban communities, the use of a water supply scheme with a community or community as a whole will greatly increase the utilization rate of the equipment and the energy saving ratio, and reduce the initial investment and area.

1. The advantages of frequency conversion constant pressure water supply instead of traditional constant pressure water supply

1. The frequency conversion constant pressure water supply can automatically maintain a constant pressure for 24 hours, and automatically start the backup pump according to the pressure signal. The pressure is adjusted steplessly. The quality of the water supply is good. Compared with the traditional water supply, it will not cause the pipe network to break and the resonance phenomenon when the water is opened. .

2. Avoid the frequent start and stop of the pump, and start smoothly, reduce the starting impact of the motor water pump, increase the service life of the motor water pump, and avoid the water hammer phenomenon in the traditional water supply

3. The traditional water supply is designed with a water tank, which not only wastes money and occupies a large space, but also has unstable water pressure, polluted water quality, and does not meet sanitary standards. The use of frequency conversion constant pressure water supply, such problems are solved. .

4. Using frequency conversion constant pressure water supply, the system can automatically detect and control the motor speed according to the actual consumption of the user to achieve the energy saving effect. It avoids the phenomenon of always turning on a pump when the water tower is unattended, saving manpower and material resources

5. The frequency conversion constant pressure water supply can automatically realize the multi-pump circulation motion function, which extends the service life of the motor water pump.

6. The frequency conversion constant pressure water supply system has complete protection functions and reliable operation. It has functions such as undervoltage, overcurrent, overload, overheat, phase loss, and short circuit protection.

2. Working principle

The frequency conversion constant pressure water supply system uses a potentiometer to set the pressure (it can also use the internal set pressure), a pressure sensor (feedback of 4~20mA or 0-10V) is used to detect the pressure in the pipe network, and the pressure sensor sends the signal into Inverter PID loop, after PID loop processing, send a water increase or decrease signal to control the motor speed. If the pressure is still insufficient or too large within a certain delay time, the power frequency/frequency conversion is switched through the PLC to make the actual pipe network pressure consistent with the set pressure.

In addition, with the reduction of water consumption, the inverter automatically reduces the output frequency, achieving the purpose of energy saving.

3. Scope of application

The use of frequency conversion constant pressure water supply has the advantages of high efficiency, energy saving, stable pressure, reliable operation, simple operation, convenient installation, less space occupation, low noise, no pollution, low investment and high benefit. Especially suitable for:

1. Domestic water supply and hot water heating systems in hotels, office buildings, apartments, residential quarters and other places.

2. Fire water supply system for high-rise buildings and large civil buildings.

3. Industrial and mining production enterprises

4. Various types of waterworks

Application of Oulun Frequency Converter in Constant Pressure Water Supply

1. Features of frequency conversion constant pressure water supply

1. Energy saving, which can save 20%-40% of electricity and realize green electricity consumption.

2. Small footprint, low investment and high efficiency.

3. Flexible configuration, high degree of automation, complete functions, flexible and reliable. 4. The operation is reasonable. Because it is soft start and soft stop, it can not only eliminate the water hammer effect, but also reduce the average torque and wear on the motor shaft, reducing the amount of maintenance and maintenance costs, and the life of the pump is greatly improved. 5. Since the frequency conversion and constant pressure speed regulation directly supply water from the water source, the secondary pollution of the original water supply method is reduced, and the source of many infectious diseases is prevented. 6. Through communication control, unattended operation can be achieved, saving manpower and material resources. Second, the principle of energy saving is known from the working principle of the water pump: the flow rate of the water pump is proportional to the speed of the water pump (motor), the head of the water pump is proportional to the square of the speed of the water pump (motor), the shaft power of the water pump is equal to the product of the flow rate and the head, Therefore, the shaft power of the water pump is proportional to the third power of the speed of the water pump (that is, the shaft power of the water pump is proportional to the third power of the power supply frequency). According to the above principle, it can be known that changing the speed of the water pump can change the power of the water pump. Flow basic formula: Q∝N H∝N2 KW=Q*H∝N3 and above Q represents flow, N represents speed, H represents head, and KW represents shaft power. For example: reduce the power supply frequency from 50HZ to 45HZ, then P45/P50=(45/50) 3=0.729, that is, P45=0.729 P50; reduce the power supply frequency from 50HZ to 40HZ, then P40/P50=(40/50) 3= 0.512, that is, P40=0.512 P50. The water pump is generally considered according to the maximum working conditions of the water supply system during design. However, in actual use, the water system may not reach the maximum amount of water for a long time. Generally, the valve is adjusted to increase the resistance of the system to throttle. It causes loss of power consumption of the motor, and the use of frequency converters can make the system work smoothly and stably. The water supply can be adjusted by changing the speed, and the investment can be recovered by reducing the speed to save energy. From the figure below we can visually see the comparison of the three flow control methods. Comparison table of actual measurement of power consumption of three flow control methods of 100KW:

Flow% Inverter shaft power KW% Input valve control

Shaft power KW% output valve control

Shaft power KW% Ideal shaft power KW%

50 15 60 84 12.5

60 25 64 89.5 21.6

70 38 68 95 34.3

80 55 72.5 99.5 51.2

90 79 84 103.5 73

100 108 106 107 100

Many motor-driven equipment have the problems of large total margin, low working efficiency, large electric energy consumption, large starting current, and large working noise. And continue to affect the economic benefits of the enterprise, and investing in inverters can fundamentally solve these problems. Under normal circumstances, the process conditions can be completely improved, and the investment recovery period does not exceed 10 months. 3. Main application occasions of frequency conversion constant pressure water supply equipment 1. High-rise buildings, urban and rural residential areas, enterprises and institutions, etc.; 2. Various industries need constant pressure control water, cooling water circulation, heating network water circulation, boiler water supply, etc.; 3 1. Central air-conditioning system; 4. Water plant booster system; 5. Farmland irrigation, sewage treatment, artificial fountain; 6. Various fluid constant pressure control system.

Fourth, the frequency conversion constant pressure water supply equipment system frequency converter is the core part of the entire frequency conversion constant pressure water supply system. Its system composition: The pump motor is the output link, the speed is controlled by the frequency converter, and the variable flow constant pressure control is realized. The frequency converter accepts the signal from the PID controller to control the speed of the water pump. The pressure sensor detects the water outlet pressure of the pipe network and transmits the signal to the PID controller. The PID controller adjusts the frequency of the frequency converter to control the speed of the water pump to achieve a closed-loop control. system. Due to the PID adjustment function of Oulun frequency converter itself, the external PID regulator can be omitted, and the adjustment is more stable.

Fifth, the simple use example of PID

(1) Assuming that the feedback channel is selected (0-10V), the range of the remote transmission pressure gauge is 0-1MPA

(2) Wiring

(3) The set parameters are as follows:

1, F0-01 is actually required, generally set to external terminal control, that is F0-01=2,

2. F0-10=8 The output frequency is determined by PID output;

   F0-11=3 PID start, that is, MI1 function is selected as PID start function;

3. F0-13=1 PID input selection, 0 indicates the source of PID setting value, set by F0-13; 1 indicates the source of PID feedback value, and analog input VI is the source;

4. F0-17=50% set value source (system requires pressure of 0.5MPa)