基于PLC的恒压供水系统设计

基于PLC的恒压供水控制系统设计

摘 要

本文主要针对当前供水系统中存在的自动化程度不高、能耗严重、可靠性低的缺点加以研究，设计出一种在这三个方面都有所提高的PLC控制的恒压供水系统。

恒压供水系统是当今应用最广泛的节能型供水系统。本文通过对供水系统运行特征及工作状态的分析，阐述了系统的节能原理，介绍了系统的基本构成及特点。并从实际出发，通过对PLC，变频器，离心水泵等原理的介绍，阐述了整个系统实现的理论基础，通过具体编制PLC程序，实现了控制要求，较好的满足了工艺要求。

在变频调速恒压供水系统中，单台水泵工况的调节是通过变频器来改变电源的频率来改变电机的转速 ，从而改变水泵性能曲线得以实现的。分析水泵工况的能耗，可以看出利用变频调速实现恒压供水，当转速降低时，流量与转速成正比，功率以转速的三次方下降，与传统供水方式中用阀门节流方式相比，在一定程度上可以减少能量损耗，能够明显节能。

关键词： 恒压供水，变频调速 ，节能 ，PLC控制

I

Design of Constant Pressure Water Supply Control

System Based on PLC

Abstract

In the thesis, the disadvantages and problems need to be resolved of current supporting water system are briefly analyzed, and a new system, which has great advance in automation, reliability and saving energy, is studied and described.

Constant pressure water supply system is widely used energy saving water supply system in today’s society. This paper describes the theory of energy saving through analyzing the system’s feature and working status, also introduces the system’s basic configuration and function. The research collectively utilized some modern control devices, such as PLC, frequency conversion device, sensor, and their program control method, all of these are of some reference value to the study of relative control system. The theory foundation of the whole system is explained practically through the introduction of the principle of PLC, frequency conversion, as well as pump.

In the frequency control water supply system, a single pump operating conditions by adjusting the frequency converter to change the power to change the motor speed, thus changing the pump performance curve can be realized. Analysis of the energy consumption of pump condition

II

comparison , you can see using frequency control constant pressure water supply, when the speed decreases, the flow and speed is proportional to the cube of power to speed down, and traditional water supply using the valve section flow method, compared to a certain extent, reduce energy consumption, energy saving can be significant.

Keywords:constant pressure water supply ,frequency control ,energy saving ,PLC control

III

目 录

摘 要 ............................................................... I Abstract ............................................................ II 第1章 绪 论 ......................................................... 1

1.1 PLC恒压供水的产生背景 ........................................ 1 1.2 PLC恒压供水的研究现状 ........................................ 2 第2章 恒压供水控制系统工艺 .......................................... 3

2.1 供水系统的工艺流程............................................ 3 2.2 供水系统的特性与工作点........................................ 3 第3章 恒压供水系统的控制方案设计 .................................... 6

3.1 系统方案的总体设计............................................ 6 3.2 所需参数计算.................................................. 7 3.3 系统中PID控制的实现.......................................... 8 3.4系统运行过程 .................................................. 9 第4章 设备选型 .................................................... 11

4.1离心泵机组选型 ............................................... 11

4.1.1 离心泵的基本构造 ....................................... 11 4.1.2 离心泵机组的选型 ....................................... 13 4.2 变频器的选型................................................. 14 4.3 压力变送器和液位传感器的选型................................. 19

4.3.1压力变送器的选型........................................ 19

IV

4.3.2液位传感器的选型........................................ 22 4.4 电接点压力表的选型........................................... 23 4.5 PLC的选型 ................................................... 25

4.5.1 PLC在本系统设计应用中的优势............................ 25 4.5.2 PLC的选型.............................................. 26 4.6 PLC扩展模块EM235、EM223..................................... 27

4.6.1 EM235的功能特性........................................ 27 4.6.2 EM235的技术规范........................................ 28 4.6.3 EM235的校准及配置...................................... 30 4.6.4 EM223的技术规范........................................ 30

第5章 恒压供水控制系统硬件及软件设计 ............................... 34

5.1系统硬件电路的设计 ........................................... 34

5.1.1 电气控制系统原理图 ..................................... 34 5.1.2 控制系统的I/O点及地址分配 ............................. 35 5.1.3电气控制回路接线图...................................... 36 5.2 系统软件程序的设计........................................... 36 参考文献 ............................................................ 41 谢 辞 ............................................................... 42

V

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