本科生毕业（设计）论文基于plc的自动恒压供水系统设计(定稿).docVIP

基于PLC的自动恒压供水系统设计 摘 要 在传统的学校供水系统中,由于用水高峰比较集中,使得供水系统工作不稳定。因此,有必要对供水系统进行改造。采用西门子S7-300 PLC和MM440变频器为主控单元,构建一个PLC自动控制的变频恒压供水系统,充分发挥PLC扫描精度高﹑运算能力强等优点,为学校供水系统提供了一套全新的方案。 本设计在学校供水系统的改造中得到了成功的应用，不仅供水压力稳定，满足学校用水需要，而且很好地显示出节能、节水的良好效果。另外该设计采用的MM440系列变频器和S7-300系列可编程控制器具有很好的性能，而且使用方便，价格适中，所以极具推广价值。 关键词: 变频器 PLC控制 恒压 转速调节 PID控制 Abstract In the traditional water supply system in school, because the many users needs water during the rushing hour time, the efficiency of water supply system not stable, so it not be satisfied the demand of all students and teachers. Therefore, it is necessary to transform the water management system. I describe the way to construct the follow-up pressure water supply system. Based on the PLC technology and frequency converter, it provides a new satisfactory pressure control solution for the water supply system by exerting the high scanning accuracy and the great operation capabilities of S7-300. This design is applied successfully in the reform of supplying water system in the school. The answer which satisfy the demands of water in the school; furthermore, it has effective in energy and doesn’t waste the water. Those people who want to reform their supplying water system can also use it. Moreover this design uses the MM440 series frequency changer and the S7-300 series programmable controller has the very good performance, moreover the easy to operate, the price is moderate, therefore has the promoted value extremely. Keywords: frequency converter, PLC control, follow-up pressure, variable-speed control，PID control 目录 摘要 I Abstract II 目录 III 前言 1 1 变频控制理论概述 3 1.1 变频调速的概念 3 1.1.1 转速和频率的关系 3 1.1.2保持的控制方式 3 1.2 PID功能简介 4 1.3 恒压供水闭环系统的PID调节过程 5 1.4 变频器的节能功能 8 1.4.1 降压节能的原理 8 1.4.2 从机械特性看压降节能的原理 8 1.4.3 变频调速与二次方律负载 9 1.5彻底消除供水系统中的水锤效应 10 2 供水系统的总体方案设计 11 2.1 供水系统的具体要求 11 2.2 变频恒压供水系统原理 11 2.3 变频恒压供水系统供水特点 12 2.4水压控制信号算法处理 13 2.5 变频恒压供水控制方式比较和选择 13 2.6 变频调速恒压供水系统工作方式 16 3 供水系统硬件软件设计 18 3.1 系统硬件设计 18 3.1.1 供水系统主电路 18 3.1.2 MM440变频器简介 19 3.1.3 S7-300 PL