Application Of PLC In The Control Of Constant Pressure Water Supply System In Xiamen Airport Living Zone

Based on its high reliability, high ratio of performance to price, broader adaptability in industry spot and convenient technique expansibility, PLC achieves much broader application in the automation process control in industry, and is superior to traditional relay control.The variable frequency constant pressure automation water supply system is the mechanical and electronic integration system that adopts the AC variable frequency speed governing and PLC technology to achieve the automatic water supply. With the combination of PLC control technology, variable frequency technology and pump groups, the system can adjust the speed of the pump and achieve the constant pressure water supply with high efficiency and energy saving according to the water consuming condition in the water flow pipe. This paper brought forward a variable frequency project which is a closed loop PID system controlling the water supply pressure. This system realizes the switch between the variable frequency and ac power frequency, makes every pump motor achieve soft start, makes one transducer convert one pump's frequency, so this system solves the compact of water hammer in the motor and avoids frequent starting of the motor. This system has the characteristics of energy saving, good adjustment, good control flexibility and high operation reliability. This system adjusts the speed of the pump motor automatically according to the change of the water consuming condition of the flow pipe so as to keep the preset constant water pressure and required flux, and can be used in the residence community and fire protection places.This paper talks about the application of PLC in the control of variable frequency constant pressure automation water supply system in the pump station of Xiamen airport living zone. This paper has discussed in details the aspects about characteristics of variable-frequency constant- pressure water supply, common used control strategy, technical flow of water supply, PLC and variable frequency technology, the makeup of PLC control system, the selection and connection of system hardware, the design of system programs, the PID control arithmetic and so on. This paper also brought forward the solutions to the problems which were met in practical project application. This system has achieved good control effect and realized the anticipative design requirements.