plc变频调速恒压供水系统设计1.doc

PLC变频调速恒压供水系统设计 此文档word版本下载后可任意编辑修改 摘要 建设节约型社会，合理开发、节约利用和有效保护水资源是一项艰巨任务。由于传统供水方式的缺陷，本文设计了一套PLC控制的变频调速恒压供水系统。 恒压供水是指在供水网系中用水量发生变化时，出口压力保持不变的供水方式。系统由可编程控制器、变频器、水泵电机组、压力变送器等构成。共三台电机，其中由一台变频器拖动2台电动机的起动、运行与调速，1台电机备用。控制系统中采用德国SIEMENS公司的S7-300可编程控制器来控制水泵电机的投入台数及运行方式；同时利用其中的数字PID控制器，由FB41将压力给定值与测量值的偏差进行处理，实时控制变频器的输出频率，进而改变水泵电动机的转速来改变水泵出水口流量，实现管网压力的自动调节，使管网压力稳定在设定值附近。此方法具有短路保护、过载保护功能，工作稳定可靠，大大延长了电机的使用寿命。 关键词： PLC；变频调速；恒压供水 The Constant Pressure Water Supply System Design Abstract Building the conservation-oriented society, the reasonable development, saves and the effective protecting water resources is an arduous task. As a result of the flaw of the tradition water supply system, a set of PLC controls frequency conversion velocity modulation constant pressure water supply system is designed. Constant pressure water-supply means that the water supply networks in the event of changeable water consumption, but the exports still remain the same pressure. The component of this system includes the PLC, tranducer, pump motor group, and the pressure sensor. This design uses one transducer drivers 2 Motors starting, running and speed control. Another motor is used to be reserved. The control system used S7-300 programmable controller which be made in Germany SIMENS corporation. Through the PID controllers, pressure will be given the fixed value and processing error of the measurement by FB41. Using the controllers to control the voltage and frequency of the frequency converter in real-time and then change the pump motor Speed to change the pump outlet flow, the pressure on the pipe network to achieve automatic adjustment so that the pressure pipeline network settings stability in the vicinity. the auxiliary pump soft start, has the short circuit protection, the overflow protection function stably, the work reliable, lengthened electrical machinerys service life greatly. Key words: PLC; constant pressure water-supply ; variable frequency speed