摘 要
在当今的社会，随着我国经济的不断的快速发展，人们的生活水平在不断地提高。城市中各类基础设施的建设发展也在快速的发展。其中也对城市住宅小区的供水系统提出的更高的要求。变频恒压控制系统是我国住宅小区广泛应用的供水系统, 传统的控制方式存在控制精度低、能耗大的缺点,研究设计的基于PLC 控制的多泵循环变频恒压供水系统, 采用可编程序控制器、变频器以及压力变送器等器件, 完成逻辑控制、变频调速和数据采样等功能, 使系统实现自动控制, 达到节能的目的, 提高了供水系统的质量。本设计根据小区的供水要求，设计了一套基于PLC的住宅小区水塔水位控制系统。该系统主要由可编程控制器（缩写为PLC）、变频器、液位开关、压力传感器及水泵等组成。
本设计通过一台变频器控制三台水泵的启停以及调速。实现了供水水泵的软启动和供水水泵的工频运行与变频运行行之间的切换。通过压力传感器检测供水管网的压力，并将测量到的水压信号反馈回PLC中，与给定值进行比较后，经过PID运算，将运算结果送入变频器，从而实现对变频器的输出电压和频率的控制，通过控制变频器的输出电压和频率，来改变供水水泵电机的转速，进而改变供水量。当有火灾发生时，使三台水泵同时处于工频运行状态，以满足消防用水。
该系统实现了居民用水的底恒压正常供水和火灾发生时的高恒压供水这俩种供水方式以及它们之间的自动切换。同时能够实现水位的自动报警等功能。本系统的设计不仅实现了供水过程的自动控制，同时也达到了节能的效益。
关键词： 可编程控制器PLC 恒压供水 变频调速
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Residential frequency constant pressure water supply system
based on PLC
Abstract
In today's society, with the rapid development of the economy of our country, people's living standard continues to improve. In the city construction and development of all kinds of infrastructure is in fast development. Higher requirements including water supply system in the city area of the proposed. Frequency conversion constant pressure control system is widely used in water supply systems in residential area in China, the traditional control method has the disadvantages of low accuracy, high energy consumption control,Multiple circulation pump frequency conversion constant pressure water supply system based on PLC control and design of the study, the use of programmable logic controller, transducer and pressure transducer devices, finish.Logic control, frequency control and data sampling function, allowing the system to achieve automatic control, to achieve the purpose of saving energy, improve the quality of water supply systems.
According to the design of residential water supply requirements, design a set of residential water tower water level based on PLC control system. The system mainly consists of a programmable controller (PLC), frequency converter, liquid level switch, pressure sensor and pump etc..
Through the design of a frequency converter to control three pump start-stop and speed. The switching between the working frequency and frequency operation, soft start and water pump water supply pump. Through the pressure sensor to detect the pressure of water supply networks, and the hydraulic pressure signal measured feedback PLC, compared with a given value, after PID operation, the operation result to the inverter, so as to realize the control of
II
output voltage and frequency of the inverter, the output voltage and frequency converter through the control, to change the water supply the water pump motor speed, and then change the water supply. When a fire occurs, so that the three pumps in the power frequency operation state at the same time, to meet the fire water.
The system realizes the automatic switching between high pressure water supply residents of the water bottom pressure of normal water supply and fire occurs when both water and their. At the same time to realize the function of water level automatic alarm. The design of the system not only realizes the automatic control of water supply process, but also to the energy saving benefits.
Keywords: Programmable Controller PLC constant-pressure frequency
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目 录
摘 要 ................................................................................................................................. I Abstract .............................................................................................................................. II 第一章 绪论 ...................................................................................................................... 1
1.1 课题产生的背景及意义 ...................................................................................... 1 1.2 变频恒压供水的国内外研究现状 ...................................................................... 1 1.3 变频恒压供水的特点及应用 .............................................................................. 3 1.4 本设计的主要研究内容 ...................................................................................... 4 1.5 系统设计的理论分析及方案的确定及变频恒压供水系统的理论分析 .......... 4
1.5.1 变频恒压供水系统的基本原理 ............................................................... 4 1.5.2 控制系统的节能原理 ............................................................................... 5 1.6 变频恒压供水系统控制方案的确定 .................................................................. 6
1.6.1 几种控制方案的比较及其确定 ............................................................... 6 1.6.2 变频恒压供水系统的组成及原理图 ....................................................... 7 1.6.3 系统中水泵切换条件分析 ....................................................................... 9
第二章 变频恒压供水系统的硬件设计 ......................................................................... 13
2.1可编程控制器PLC的选型 ............................................................................... 13
2.1.1 PLC简介 ................................................................................................. 13 2.1.2 PLC的基本组成 ..................................................................................... 14 2.1.3 PLC的工作过程 ..................................................................................... 15 2.1.4 可编程控制器（PLC）及外接模块的选型 .......................................... 17 2.2 变频器的选型 .................................................................................................... 18
2.2.1 变频器简介 ............................................................................................. 18 2.2.2 变频器的选型 ......................................................................................... 19 2.3 水泵机组的选型 ................................................................................................ 19 2.4 压力传感器的选型 ............................................................................................ 21 2.5 液位开关的选型 ................................................................................................ 21 2.6 系统主电路的分析及其设计 ............................................................................ 22 2.7 系统控制电路的分析及其设计 ........................................................................ 23 2.8 可编程逻辑控制器(PLC)的I/0端子分配 ....................................................... 26
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