恒压供水系统设计
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 control's 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 machinery's service life greatly.
Key words: PLC; constant pressure water-supply ; variable frequency speed-regulating
目录
摘要 ............................................................................................................................................. I Abstract ......................................................................................................................................II 第一章 绪论 .............................................................................................................................. 1
1.1 课题提出的背景 ......................................................................................................... 1 1.2 课题研究的目的和意义 ............................................................................................. 1 1.3 国内外在变频恒压供水系统研究现状及分析 ......................................................... 2
1.3.1 变频恒压供水系统的国内外研究现状 .......................................................... 2 1.3.2 可编程序控制器技术国内外发展现状 .......................................................... 3 1.4 设计主要内容 ............................................................................................................. 4 第二章 恒压供水基本原理 ...................................................................................................... 6
2.1 供水系统简介 ............................................................................................................. 6 2.2 恒压供水基本原理 ..................................................................................................... 6
2.2.1 恒压供水原理 .................................................................................................. 6 2.2.2 系统结构框图设计 .......................................................................................... 6 2.3 恒压供水的优点 ......................................................................................................... 8 2.4 本章小结 ..................................................................................................................... 9 第三章 恒压供水系统部件选择 ............................................................................................ 10
3.1 变频恒压供水系统的构成 ....................................................................................... 10
3.1.1 变频恒压供水系统硬件结构 ........................................................................ 10 3.1.2 恒压供水系统构成 ........................................................................................ 11 3.2 S7-300系列PLC简介 .............................................................................................. 12
3.2.1 S7-300的概况 ................................................................................................. 12
3.2.2 S7-300 的模拟量输入/输出模块 ................................................................... 14 3.2.3 S7-300 的PID模块FB41 ............................................................................. 17 3.3 变频器的介绍 ........................................................................................................... 17
3.3.1 选择变频器规格 ............................................................................................ 17 3.3.2 开关指令信号的输入 .................................................................................... 18 3.3.3 变频器与PLC的连接 ................................................................................... 19 3.4 传感器 ....................................................................................................................... 19 3.5 本章小结 ................................................................................................................... 21 第四章 恒压供水系统软件设计 ............................................................................................ 22
4.1 系统设计 ................................................................................................................... 22
4.1.1 系统主电路的设计 ........................................................................................ 22 4.1.2 PLC控制电路设计 ......................................................................................... 23 4.2 程序设计 ................................................................................................................... 24
4.2.1 控制系统主程序设计 .................................................................................... 24 4.2.2 水泵电机切换程序 ........................................................................................ 25 4.2.3 西门子S7300系列PLC通信程序设计 ....................................................... 27 4.2.4 量程转换程序设计 ........................................................................................ 29 4.3 PID设计 ..................................................................................................................... 29
4.3.1 PID控制 .......................................................................................................... 29 4.3.2 恒压供水PID调节过程分析 ........................................................................ 31 4.3.3 PID控制器的应用 .......................................................................................... 31 4.4 本章小结 ................................................................................................................... 32 第五章 总结 ............................................................................................................................ 33
