【正文】 根據(jù)城市居民用水標準為前提和小型自來水廠的供水要求，自行設計了基于 PLC變頻調(diào)速恒壓供水系統(tǒng)。恒壓供水系統(tǒng)是指用戶端在任何時候，不管用水量的大小，總能保證管網(wǎng)中的水壓恒的基本定。 本系統(tǒng)是用 3 臺水泵電機的變頻循環(huán)運行方式，變頻器和 PLC 作為系統(tǒng)控制的核心部件，時刻跟蹤壓力變送器檢測到的管網(wǎng)壓力和給定壓力的偏差變化，經(jīng) PLC 內(nèi)部進行 PID 運算，通過 PLC 控制變頻和工頻的切 換，自動控制水泵的投入臺數(shù)和 控制變頻器的輸出頻率，進而改變水泵電機的轉(zhuǎn)速來改變供水量，最終保持管網(wǎng)壓力穩(wěn)定在設定值附近 。 關(guān)鍵詞： PLC、變頻調(diào)速、恒壓供水系統(tǒng)、壓力變送器、液位變送器 基于 PLC 變頻調(diào)速恒壓供水系統(tǒng)設計 II ABSTRACT This paper is based on residential water standards for water supply requirements of the premise and waterworks, to design a PLCbased frequency control water supply system. Water Supply System means the size of the client at any time, regardless of water use, always ensure that the water pressure constant in the pipe work in the set. Frequency control water supply system uses PLC, inverter, pressure transmitter, and the pump unit to form a closed loop control system using PLC logic control, the inverter speed control of pump units. This system is the conversion cycle operation mode of the water pump motor, inverter and PLC as the core ponent of the system control keeps track of pressure transmitter detected the pipe work pressure and a given pressure change in error, the PID by the PLC internal operation by the PLC to control the switching of the variable frequency and power frequency, automatic control of pump input the number of units and control of inverter output frequency, and thus change the speed of the pump motor to change the supply quantity, and ultimately to maintain the stability of the pipe work pressure near the set value. This system uses the converter to achieve softstart and frequency control threephase water pump motor run switch using the principle of first initial first stop to avoid the longrunning of the pump and cause damage and reduce the life of the motor, but also increase a realtime monitoring of the level transmitter pump into the empty pumping of water to prevent pump damage to the pump motor and alarm system is the response system is functioning properly, whether the pump motor overload, the inverter is abnormal. Keywords:PLC, Frequency Control, Water Supply System, pressure transmitter, level transmitter 華北科技學院畢業(yè)設計 目 錄 1 緒論 ........................................................................................................................................ 1 選題的背景和意義 ...................................................................................................... 1 變頻恒壓供水的特點及應用 ...................................................................................... 1 變頻恒壓供水代替?zhèn)鹘y(tǒng)恒壓供水的優(yōu)點 ........................................................ 1 變頻恒壓供水的特點 ........................................................................................ 2 變頻調(diào)速恒壓供水的應用 ................................................錯誤 !未定義書簽。 變頻調(diào)速技術(shù)的發(fā)展狀況 ................................................錯誤 !未定義書簽。 變頻恒壓供水系統(tǒng)的發(fā)展趨勢 ........................................錯誤 !未定義書簽。 2 變頻恒壓供水系統(tǒng)的理論分析 ............................................................................................ 3 系統(tǒng)概 述和節(jié)能原理 ................................................................................................... 3 系統(tǒng)概述 ............................................................................................................ 3 節(jié)能原理 ............................................................................................................ 4 電動機的調(diào)速原理 ....................................................................................................... 5 變頻恒壓供水系統(tǒng)的控制方案 .................................................................................. 5 控制方案的選擇 ................................................................................................ 6 系統(tǒng)的組成及原理圖 ........................................................................................ 7 系統(tǒng)控制流程 .................................................................................................... 9 水泵切換條件分析 .......................................................................................... 10 3 系統(tǒng)的硬件設計 .................................................................................................................. 12 供水設備的選擇原則 ................................................................................................ 12 系統(tǒng)主要設備的選型 ................................................................................................ 13 PLC 及其擴展模塊的選型 ............................................................................ 14 變頻器的 選型 ................................................................................................ 17 壓力變送器的選型 ........................................................................................ 21 基于 PLC 變頻調(diào)速恒壓供水系統(tǒng)設計 液位變送器的選型 .........................................................................................21 系統(tǒng)主電路、控制電路分析及其設計 .....................................................................23 系統(tǒng)主電路分析及其設計 .............................................................................23 系統(tǒng)控制電路分析及其設計 .........................................................................25 PLC 的 I/O 分配及外圍接線圖 ...............................................................................27 4 系統(tǒng)的軟件設計 ...................................................................................................................30 系統(tǒng)軟件設計分析 .....................................................................................................30 PLC 程序設計 .............................................................................................................31 控制系統(tǒng)主程序設計 ........................................................................................32 控制系統(tǒng)子程序設計 ........................................................ 錯誤 !未定義書簽。 PID 控制及其控制算法 ..................................................... 錯誤 !未定義書簽。 PID 參數(shù)整定 .