China's urbanization rate has been increasing year by year, and high-rise buildings are being constructed in cities. With this, the construction of fire-fighting projects has attracted more and more attention from all walks of life. In the current water fire fighting, the frequency conversion speed regulation pump technology has been widely used. Its wide frequency conversion range can meet the requirements of different fire protection environments. This article will discuss and analyze the application of variable frequency speed regulating pump in water fire protection.

1 Overview of variable frequency speed regulating pump

At present, there are more and more high-rise buildings, and the problem of building fire protection has become a concern of society. Frequency conversion and constant pressure automatic water supply is widely used due to its excellent performance. The automatic water supply control system can collect pressure data of the pipe network through pressure sensors, convert them into controllable signals for automatic frequency conversion control. Through this system design, the variable frequency constant pressure water system can replace water towers and high-rise water tanks to provide water for building water fire protection, effectively improving the efficiency and quality of building fire protection. In addition, the power consumption of the variable frequency speed governing pump is directly proportional to the cube of the speed of the motor, so the energy consumption of the variable frequency speed governing pump is low, and the energy saving effect is very obvious. The frequency conversion speed-adjustable water pump combined with the programmable controller can realize the circulating frequency conversion of the water pump and the soft start of the motor, extend the use time of the equipment, and greatly improve the stability of the system work. In the fire water supply water, it is better to use frequency conversion control for the constant pressure pump and during the fire pump inspection, but in the fire pump fire control, the direct start or reduced pressure start control method should be used.

2 Application analysis of variable frequency speed regulating pump in fire fighting

2.1 Application analysis of water-fighting medium frequency variable speed pump

In the ordinary fire water supply system, the fire protection system pipe network is mainly stabilized by the booster and pressure-stabilizing pump, so that the fire protection system maintains the state of fire water pressure preparation to ensure that the system can respond to sudden fires in a timely manner. If a fire occurs in a building, a technician can start a variable-frequency speed-adjusting fire pump to provide the building fire-fighting water pressure and water flow in a timely manner. According to China's fire-fighting regulations, the maximum working time of water firefighting is limited to 2.5 hours, and the energy consumption of the fire pump of the system needs to be considered. The fire pump shall be provided with a backup pump, and the backup pump shall not be less than any one main fire pump. According to the multi-pump parallel constant-pressure water supply theory, the multi-pump parallel constant-pressure water supply, the variable frequency speed regulating pump must be the largest one of the pumps, and the other parallel pumps are automatically controlled by the variable frequency controller according to the water flow change. Failure of the variable frequency pump may cause the frequency converter to trip and stop all fire pumps. From this point of view, the use of variable frequency speed regulation for fire pumps will reduce the reliability of fire water supply and should not be used in water fire protection systems. There are various means for adjusting the rotation speed of the three-phase motor, for example, the adjustment of the rotation speed is achieved by adjusting the frequency of the alternating current, the number of poles of the motor rotor, and the difference in rotation. Generally, technicians adjust the motor speed by adjusting the number of poles of the motor. In the previous water fire protection systems, it was relatively rare to adjust the transfer speed by using frequency. With the rapid development of power electronics systems and information science, and the progress and development of variable frequency control technology, researchers have used the water frequency control of AC pumps to adjust the frequency of pump power in water fire protection systems to increase water supply efficiency and reduce system energy consumption. Variable speed pumps have been widely used in water fire protection systems.

2.2 Control analysis of variable frequency speed regulating pump in fire water supply system

The current variable frequency speed governing pumps for water firefighting have been widely used. There are many control methods in the variable frequency speed-regulating pump, mainly including the following methods:

(1) Relay contactor control. This is the simplest control method. According to fire-fighting conditions or changes in the external environment, according to the analog technology, you can use relay contactors to run the pump motor to achieve the purpose of frequency conversion.

(2) Digital circuit control. The control circuit of the digital circuit variable speed pump is fixed in the frequency conversion state, and the other water supply pumps are in the working frequency band state. Its control method is relatively new and advanced, but the water supply pumps are all soft-started, and the full-flow frequency change adjustment cannot be controlled in this way. Therefore, the accuracy of its control is relatively low, the pressure fluctuation of the pump is large during switching, and the debugging is relatively troublesome. The power frequency pump has a weak ability to resist shock and clutter when it starts. The cost of this control system is low. When the pressure of the fire-fighting water-saving pipe network drops to the prescribed threshold, the water pressure signal is transmitted through the pressure sensor and the stabilizing pump is automatically started to supplement and pressurize the fire-fighting pipe network. When the pressure on the official website reaches the maximum threshold, the water supply is automatically stopped . The technicians can set the system of the fire-fighting center linkage interface according to the situation of the job site. After the fire-fighting hydrant button of the fire-fighting center starts to send out a fire alarm signal, the electronic control system automatically starts the frequency-variable fire-fighting main pump to extinguish the fire.

(3) Integrated circuit control. The use of a single-chip microcomputer or other integrated circuits for frequency control of water fire frequency conversion pumps has better control effects than logic electronic circuits, but it is relatively troublesome to debug and maintain in different areas of the pipe network and different water supply modes. Because the control program is pre-programmed in the control chip, when the system is upgraded or added functions, the circuit board needs to be replaced or modified again, and the technician needs to re-set the system program, so this control method is more convenient. In addition, the reliability and anti-interference ability of the integrated circuit control cannot meet the control of the variable frequency speed regulating pump in a complex environment. In the system, the water pump plays a role of supplementing the pressure of the fire water supply to meet the demand of the water supply unit for the pressure of the water supply. The energy storage tank can store and receive the energy from the tap water pipe network, and can also play a role in reducing the impact on the pipe network when the pump is started. The pressure sensor is used to receive the pressure information of the user's pipe network and control the speed of the water pump. The energy regulator receives the pressure information of the water pipe network, and adjusts and controls the pump to make full use of the energy of the pipe network to avoid damage and impact on the pipe network. The control cabinet is used to receive the information from the pressure sensor, and then to control the operation of the variable frequency speed regulating water pump after scientific processing. The core component of the equipment is the energy regulator, which has 3 pressure values that can be set arbitrarily. It can generate 4 pressure measurement points by intersecting with the pressure value of the water pipe network. Monitoring the pressure of the pipe network is monitored and data collected by the energy regulator at all times. Every time a relevant value is monitored, a scientific judgment needs to be made, and the result of the judgment data needs to be transmitted to the frequency conversion control system of the host group, which can achieve the purpose of automatic pressure compensation.

2.3 Application of variable frequency speed regulating pumps in different distribution forms of fire water supply

变频 In the application of variable frequency speed governing pumps, when a community only uses a pressurized pump room, the pump is used for centralized pressurization to supply water to the buildings in the community. According to whether the domestic water pump and the fire pump work normally, determine whether the two official websites are separately set up and arranged. The fire protection system needs to ensure that the entire residential area has at least a complete fire-fighting water supply system. The variable-frequency speed-regulating fire pump is used to deliver fire-fighting water to the fire-fighting pipe network in each building in the residential area. Each building has at least one roof water tank on the roof. The initial fire fighting water must be stored. When the inverter of the variable speed pump is integrated, it can integrate the functions of PID and PLC into the inverter of the variable speed pump in an integrated way to form an application-oriented control inverter. Because the PID calculation has been solidified in the inverter before, the programming design of the PLC and the design of the PID are omitted, and the PID parameters are relatively easy to debug online. The built-in PID regulator uses an optimization algorithm to ensure that the water pressure regulation in water fire fighting is maintained in a smooth and stable state. In the water fire frequency conversion pump, to ensure that the signal value of the water pressure feedback on the official website is accurate, it is necessary to set a constant for the filtering time. At the same time, the signal value of the system feedback needs to be scientifically converted to make the fire system debugging and operation easier. Convenience. The constant pressure water supply equipment produced by the inverter with built-in PID function can reduce equipment cost and save installation and commissioning time. In addition, in view of the shortcomings of traditional variable frequency speed regulating water supply equipment, some products are designed with variable frequency speed regulation and intelligent control technology, so multi-level direct high-voltage frequency converters, fuzzy controllers and other devices have been applied. Such as the use of multi-level high-voltage inverter, can achieve high efficiency power input, output, high quality factor and continuous and stable operation of the system. The fuzzy controller can adapt to the changes of the controlled system to the maximum extent, and achieve the control purpose of high precision, fast response and simple control law. Speed adjustment of speed governing water pump cannot be adjusted arbitrarily. The speed regulating water pump needs to maintain a certain head, and the speed may not be reduced by too much. When the pump speed adjustment range is exceeded, it is difficult for the system to ensure efficient work. When the system is running for a long time, it will cause a large waste of energy. Therefore, the design condition of the pump should be as far as possible to meet its work in the efficient speed regulation range. Through scientific design, it is ensured that the variable frequency speed regulating pump plays the greatest role in water fire protection.

Concluding remarks

With the rapid development of science and technology, the frequency control methods and technical methods of frequency conversion speed-adjusting pumps for water fire fighting are constantly increasing. Through scientific control in the variable frequency speed regulating pump, it can effectively improve its working efficiency and reduce energy consumption, and ensure that the fire protection system works under the optimal conditions.