【正文】 m variable frequency operation mode to work frequency operation mode. In addition，the bination of the system and the puter is achieved，which improved the overall function of the system．Key words：PLC。給出了實現(xiàn)有效狀態(tài)循環(huán)轉換控制的電氣設計方案和 PLC 控制程序設計方案。本文根據(jù)城區(qū)供水管網(wǎng)改造工程設計了一套由 PLC、變頻器、遠傳壓力表、多臺水泵機組、計算機等主要設備構成的全自動變頻恒壓供水及其遠程監(jiān)控系統(tǒng)，具有自動工頻/變頻恒壓運行、可實現(xiàn)遠程自動控制和現(xiàn)場手動控制等功能。供水的可靠性、穩(wěn)定性、經(jīng)濟節(jié)能性直接影響到城區(qū)的建設和經(jīng)濟的發(fā)展，也影響到城區(qū)居民的正常工作和生活。 論文論述了采用多泵并聯(lián)供水方案的合理性，分析了多泵供水方式的各種供水狀態(tài)及轉換條件，分析了電機由變頻轉工頻運行方式的切換過程及存在的問題。關鍵詞：PLC ；變頻調速；恒壓供水；變頻工頻切換Abstract With the continuous deepening of reforming and opening up, the construction and economy of small and mediumsized cities in China have developed rapidly. People39。 variable frequency to working frequency目錄摘 要 ........................................................................................................................IABSTRACT .............................................................................................................II1 緒 論 .....................................................................................................................1 課題背景及意義 ................................................................................................1 變頻恒壓供水的現(xiàn)況 ........................................................................................1 變頻恒壓供水系統(tǒng)的特點 ................................................................................32 變頻恒壓供水系統(tǒng)理論分析 ...............................................................................4 供水系統(tǒng)的基本特性 ........................................................................................4 不同控制方式下的能耗分析與比較 ................................................................5 變頻恒壓控制的理論模型 ................................................................................6 供水系統(tǒng)中的水錘效應及消除方法 ................................................................73 供水系統(tǒng)恒壓控制與硬件設計 ...........................................................................8 異步電動機調速方法及選型 ............................................................................8 變極調速 .........................................................................................................8 變頻調速 .........................................................................................................9 供水系統(tǒng)的方案確定 ......................................................................................10 供水系統(tǒng)的流量類型 ...................................................................................10 總體設計方案確定 ........................................................................................10 恒壓供水電控系統(tǒng)組成 ................................................................................12 控制系統(tǒng)的硬件設計與選型 ...........................................................................13 主電路設計 ....................................................................................................13 電氣控制電路設計 ........................................................................................14 系統(tǒng)主要配置的選型 ....................................................................................16 PLC 的選型 .......................................................................................................19 系統(tǒng)可靠性措施 ..............................................................................................204 PLC 控制系統(tǒng)的設計 .......................................................................................22 水泵工頻/變頻運行狀態(tài)及轉換過程分析 .....................................................22 供水狀態(tài)及其轉換 ........................................................................................22 狀態(tài)轉換關系 ...............................................................................................22 狀態(tài)轉換條件 ...............................................................................................24 PLC 程序設計 .................................................................................................25 PLC 編程語言 .............................................................................................25 梯形圖語言編程的一般規(guī)則 .....................................................................25 供水系統(tǒng)控制模塊的設計 ..............................................................................26 系統(tǒng)初始化模塊 ............................................................................................26 水泵運行與狀態(tài)轉換模塊 ............................................................................265 恒壓供水系統(tǒng)的 PID 調節(jié) .................................................................................28 PID 控制及其控制算法 ....................................................................................28 恒壓供水 PID 調節(jié)過程分析 ..........................................................................29結 論 .......................................................................................................................31附 錄 .......................................................................................................................32致謝 .........................................................................................................................34參考文獻 .................................................................................................................3511 緒 論