Background of constant pressure water supply
With the rapid development of the social economy in recent years, various parts of the country have experienced rapid urbanization, with a rapid increase in urban population, rapid expansion of urban scale, and continuous growth and breakthroughs in the size and height of urban buildings. These growth demands higher and higher demands on urban water supply systems.
The current development trend of water supply methods for social and economic needs is generally towards the direction of high efficiency, energy conservation, and automatic reliability. Combining constant pressure water supply with variable frequency speed regulation technology is a water supply method that can meet the trend of efficient, energy-saving, and stable and reliable development in modern society. Constant pressure water supply refers to the technology of controlling and adjusting the pressure of water supply through the feedback signal of water pressure difference, so as to maintain a stable pressure and achieve a balance between water supply and water use. Variable frequency technology refers to a technology that reduces power consumption and improves operational efficiency by controlling the power supply frequency and motor speed based on the power demand of the system.Advantages of using frequency conversion technology in water supply systems
1. Reduce current impact: The water pump and motor can achieve variable frequency start and stop, and the start and stop currents are relatively small, greatly reducing the impact current and voltage fluctuations on the power grid caused by system start and stop. 2. Reduce mechanical impact: It can reduce the impact on mechanical systems such as pipeline networks, water pumps, valves, etc., reduce maintenance workload, extend the service life of the pipeline network, and improve economic benefits. 3. Energy conservation and consumption reduction: The speed of the water pump unit can be adjusted according to the peak and valley changes in actual water demand, which has obvious energy-saving effects and improves economic benefits. 4. Improve the automation level of system operation, while also having high reliability, which can achieve unmanned work and greatly reduce the labor cost of system operation. 5. System protection: The system has multiple protection functions such as overcurrent, overload, overvoltage, undervoltage, motor phase loss, short circuit, and system overheating. 6. The system has a certain capacity for expansion and upgrading. If it needs to increase the water supply capacity, convenient expansion and technical transformation can be carried out. If the system needs to undergo unified scheduling and monitoring in the future, using the transformation can also easily achieve network monitoring function and unified scheduling.
The variable frequency constant pressure water supply system mainly consists of alarm devices, operation interfaces, communication interfaces, control systems, signal detection and execution mechanisms. The main components are shown in the following figure.
Composition diagram of constant pressure water supply method
When controlling the system, the signals we need to detect include liquid level, water pressure, and alarm signals: The so-called water pressure signal refers to the pressure value of water in the user network, which is the most important signal in constant pressure water supply control. It is actually an analog signal that is read into the PLC for A/D conversion. In addition, in order to increase the stability of the system, we also need to test the maximum and minimum water supply pressures, as well as the pressure values of the electrical contacts. The adequacy of the water inflow into the water pump is mainly reflected by the liquid level signal. When the liquid level signal is a valid signal, in order to avoid the phenomenon of empty pumping of the water pump, which may cause damage to the motor, the control system should perform the function of protecting the system. We install a liquid level sensor in the water to provide a liquid level signal.
Whether the system is operating normally, whether the frequency converter is malfunctioning, and whether the motor of the water pump is operating in an overload state can be reflected through an alarm signal, which is a digital quantity.
PLC control system configurationUsually composed of programmable controllers, frequency converters, and electrical control equipment. The most important part of controlling a variable frequency constant pressure water supply system is the water supply controller. The water supply controller collects alarm signals, liquid levels, and pressures in the system, analyzes data information from human-machine interfaces and communication interfaces, processes corresponding control algorithms, and obtains corresponding control measures. It uses a frequency converter and contactor to control the water pump. The main function of the frequency converter is to effectively regulate the rotation speed of the water pump. Its main principle is to track the control signal transmitted by the water supply controller and adjust the working frequency of the pump accordingly, thereby adjusting the working speed of the speed regulating pump. The electronic control equipment of the frequency converter includes some components such as conversion switch protection relay and a set of contactors. The main function is to effectively regulate the operation mode of the water pump, achieve manual and automatic transformation, and achieve effective control of dispersion and concentration.
Control cabinet PLC
Constant pressure water supply electric control cabinet