摘要众所周知，水和人们的生活紧密联系。离开水无人可以存活。然而为了追求经济的可持续发展，人们对原本和谐的生态环境任意践踏，带来了水资源的污染和匮乏等种种的后果。甚至连传统的供水方式都有水质易污染，能耗还多，损坏设备的弊端。总而言之，这些都无疑加重了供水问题的严重性。因此在如今高科技迅猛发展的时代，当务之急就是把这些先进技术巧妙融合到供水环节中去来缓解问题。83688

   根据变频恒压供水系统的结构和工作原理可知，变频调速不仅有利于资源更好的配置,还能节约能源。这种安全可靠的方式让供水系统在最佳条件下运行的同时，很大程度上提高了人们生活水平以及生产的效率。这次设计方案结合了PLC编程简单，耗能少，易维护，系统设计周期短等特点，将它与变频器相结合，再加上水泵机组和压力传感器等设备设计了一个操作简单的变频恒压供水系统。

本文分析了变频调速在恒压供水系统中的工作原理，并确定了它的控制方案。同时着重阐述了系统的硬件和软件设计。主要任务是编写PLC的控制程序并应用三菱软件调试，即主、自动手动控制和报警显示子程序。

毕业论文关键词：PLC；变频器；恒压供水；控制程序

Abstract   As is known to all, water and human lives are related closely。No one can survive without water。 However, in order to pursue the sustainable development of economy, people destroy the ecological environment that used to be harmonious without restraint ,which brings about the pollution and shortage of water resource and so on a series of problems。 What is worse, the traditional way of water supply has the disadvantages of easily polluted water quality , too much energy consumption and damage to the equipment。 In short, there is no doubt that this increases the severity of the problem of water supply。 So under the rapid development of high technology nowadays, it is urgent to combine these advanced technologies with the water supply link to relieve the problem。

  According to the structure and working principle of variable frequency constant pressure water supply system, it can be gotten that the frequency control of speed is not only beneficial to better deployment of resource, but also save some energy。 In this way,the water supply system runs at the best possible conditions, to a large degree,greatly improving the efficiency of people's life and production。The characters of PLC are simple programming , less energy consumption, easy maintenance and short design cycle。This design combines them with frequency converter,  the water pump unit and the pressure sensor devices to design a variable frequency constant pressure water supply system。 

  This paper analyses the working principle of variable frequency speed regulation in constant pressure water supply system, and determines its control scheme。 At the same time, the hardware and software design of the system are emphasized。The main task is to write the program of PLC control system and apply MITSUBISHI software to debug , just the main, manual and automatic control and alarm display subroutine。 

Keywords: PLC;frequency converter；constant pressure water supply;control program

目 录

第一章 绪论

1。1 变频恒压供水的开发背景和意义 1

1。2 国内外研究现状及发展趋势 2

    1。3 PLC可编程控制器 3

1。3。1 可编程控制器的发展和特点 3

1。3。2 可编程控制器的主要应用