The use of frequency converter in fire protection

- Aug 18, 2018-

1 Frequency Control Pump Overview

At present, the number of high-rise buildings is increasing, and the problem of building fire protection has become a concern of the society. The variable-frequency constant-pressure automatic water supply has been widely used due to its excellent performance. The automatic water supply control system can collect the pressure data from the pipe network through the pressure sensor, and convert it into a controllable signal for automatic frequency conversion control. Through this system design, the variable frequency constant pressure water system can replace the water tower and the high-rise water tank to provide water source 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 control pump is proportional to the cube of the motor speed. Therefore, the energy consumption of the frequency conversion speed control pump is low, and the energy saving effect is very obvious. The power consumption of the frequency conversion speed control pump is at least 35% lower than that of the ordinary water supply method. The variable frequency speed control water pump is used in combination with the programmable controller, which can realize the circulating frequency conversion of the water pump and the soft start of the motor, prolong the use time of the equipment, and can greatly improve the stability of the system operation. It is best to use variable frequency control in the fire water supply for the constant pressure pump and in the fire pump inspection, but the direct start or step down start control mode should be adopted in the fire pump fire control.

2 Analysis of the application of variable frequency speed control pump in fire protection

2.1 Application analysis of variable frequency speed control pump in water fire protection

In the usual fire water supply system, the fire protection system pipe network is mainly regulated by the booster and the constant pressure pump, so that the fire protection system maintains the fire water pressure preparation state, so as to ensure that the system can respond to sudden fires in time. If there is a fire in the building, the technician can start the variable frequency speed control fire pump to provide the building fire water with the pressure and water flow of the fire water in time. According to China's fire protection related regulations, the maximum fire fighting time is limited to 2.5 hours, and the energy consumption of the system's fire pump needs to be considered. The fire pump shall be provided with a backup pump, and the backup pump shall be not less than any of the main fire pumps. The theory of multi-pump parallel constant pressure water supply, multi-pump parallel constant pressure water supply, variable frequency speed control pump must be one of the largest pumps, and the other parallel pumps automatically input or exceed are automatically controlled by the variable frequency controller according to the change of water flow. Failure of the lead pump may cause the frequency converter to trip, causing all fire pumps to stop pumping. From this point of view, the use of variable frequency speed control of fire pumps will reduce the reliability of fire water supply, and should not be applied in water fire protection systems. There are various ways to adjust the rotational speed of a three-phase motor, for example, the adjustment of the alternating current frequency, the adjustment of the number of poles of the motor and the adjustment of the rotational speed to achieve the adjustment of the rotational speed. Usually, the technician adjusts the motor speed by adjusting the number of motor poles. In the previous water fire protection system, it is relatively rare to use the frequency to adjust the speed of the machine. Along with the rapid development of power electronic systems and information science, the frequency conversion control technology has been improved and developed. Researchers can adjust the AC frequency frequency regulation of the water pump power supply in the water fire protection system to improve the water supply efficiency of the water fire protection system and reduce the energy consumption of the system. The variable frequency speed control pump has been widely used in water fire protection systems.

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

The current water fire control medium frequency variable speed pump has been widely used. There are many control methods in the variable frequency speed control pump, mainly in the following ways:

(1) Relay contactor control. This is the simplest way to control. According to the fire protection conditions or changes in the external environment, according to the mode power technology, the relay contactor can be used to achieve the purpose of frequency conversion.

(2) Digital circuit control. The control circuit of the digital circuit to the variable frequency speed control pump is fixed in the frequency conversion state, and the other water supply pumps are in the working frequency state. The control method is relatively novel and advanced, but the water supply pump group is all soft-started, and the full-flow frequency change adjustment cannot be controlled in this way. Therefore, the accuracy of the control is relatively low, the pressure fluctuation of the pump is large when switching, and the debugging is relatively troublesome. The ability of the power frequency pump to resist shock and anti-clutter is weak when starting. This type of control system is less expensive. When the pressure of the fire-fighting water pipe network drops to the specified threshold, the water pressure signal is transmitted through the pressure sensor and the pressure-regulating pump is automatically started to perform the water-filling and pressurizing operation on the fire-fighting pipe network, and the water supply is automatically stopped when the pressure of the official website reaches the maximum threshold value. . The technician can set the system of the fire center linkage interface according to the situation of the job site. After the fire hydrant button of the fire center starts to issue the fire alarm signal, the electronic control system automatically starts the variable frequency fire main pump to perform the fire extinguishing operation.

(3) Integrated circuit control. The frequency control of water fire frequency variable frequency water pump by using single chip microcomputer or other integrated circuits has better control effect than logic electronic circuit, but it is relatively troublesome to debug and maintain under different pipe networks and different water supply modes. Since the control program is pre-programmed in the control chip, when the system is upgraded or added, the circuit board needs to be replaced or modified again. The technician needs to re-set the system program, so the control method is convenient. Poor, in addition, the reliability and anti-interference ability of integrated circuit control can not meet the control of variable frequency speed control pump in complex environment. In the system, the water pump acts as a pressure on the fire water supply to meet the fire department's demand for water supply pressure. The energy storage tank can store and receive energy from the water pipe network, and can also reduce the impact on the pipe network when the pump is started. The pressure sensor is used to receive user pipe network pressure information and control the pump speed. The energy conditioner receives the pressure information of the water pipe network, adjusts and controls the water pump to fully utilize the energy of the pipe network, and avoids damage and influence on the pipe network. The control cabinet is used to receive the information of the pressure sensor and to control the operation of the variable frequency speed control pump after scientific processing. The core component of the device is an energy conditioner, which has three pressure values that can be arbitrarily set. Four pressure measurement points are generated by intersecting the pressure value of the water pipe network. The monitoring of the network pressure is monitored by the energy regulator and data is collected. Every time a relevant value is monitored, a scientific judgment is required, and the data result of the judgment is 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 control pump in different distribution forms of fire water supply

In the application of the variable frequency speed control pump, when only a pressurized pump room is used in a certain area, the pump is used for centralized pressure to supply water to buildings in the community. According to whether the life pump and the fire pump are working properly, it is determined whether the two official websites are arranged separately and the official website is arranged. The fire protection system shall ensure that the entire community has at least a complete fire water supply system. The fire control water is used to transfer the fire water to the fire pipe network in each building in the community. Each building has at least one roof water tank in the water tank. Initial fire water must be stored. When the inverter of the variable frequency speed control pump utilizes the integrated mode, it can integrate the functions of PID and PLC into the inverter of the variable frequency speed control pump in an integrated manner to form an application-oriented control inverter. Because the PID operation has been solidified to the inside of the inverter before, the programming design of the PLC and the design of the PID are omitted, and the parameters of the PID 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 protection is kept in a smooth and stable state. In the water fire-fighting variable frequency pump to ensure the accuracy of the signal value of the official website water pressure feedback, it is necessary to set the filter time constant, and also need to scientifically convert the signal value of the system feedback, so that the fire system debugging and operation are relatively simple. Convenience. The constant pressure water supply equipment produced by the inverter with built-in PID function can reduce equipment cost and save installation and debugging time. In addition, in view of the shortcomings of the traditional variable frequency speed control water supply equipment, some products are designed with frequency control and intelligent control technology, so multi-level direct high-voltage inverters, fuzzy controllers and other devices have been applied. High-efficiency power input, output, high quality factor and continuous and stable operation of the system can be achieved with multi-level high-voltage inverters. The fuzzy controller can fully adapt to the changes of the controlled system to achieve the control aim of high precision, fast response and simple control law. The speed adjustment of the speed control pump cannot be adjusted arbitrarily. The speed control pump needs to be kept at a certain lift, and the speed may not be too large. When the pump speed range is exceeded, it is difficult to ensure efficient operation. When the system is running for a long time, it will cause a large energy waste. Therefore, the design condition of the pump should be as close as possible to work within the high efficiency range. The scientific design ensures that the variable frequency speed control pump plays the biggest role in water fire protection.

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