PLC和变频器在中央空调中应用.doc

摘 要 本文介绍了由变频器、PLC、数模转换模块、温度模块、温度传感器等组成的温差闭环控制在中央空调系统节能改造中的应用。通过温差闭环控制，使冷冻水泵和冷却水泵能随空调负荷的变化而自动变速运行，大大优化了系统的运行质量，达到了显著的节能效果。文中首先通过分析原中央空调系统及存在的问题，对系统进行节能改造的可行性分析。然后提出节能改造的具体方案，对节能改造需要的主要设备进行简单介绍。再次通过方案画出变频节能技术框图、PLC变频器节能改造原理分析、画出PLC控制梯形图、写出PLC指令表。最后列举设备调试和遇到的问题并对中央空调改造前和改造后进行运行效果比较。而文中的重点和难点是：对原系统进行节能改造的可行性分析和节能改造的具体方案的确定；变频节能技术、PLC控制原理、PLC控制梯形图和PLC指令表。 关键词：PLC 变频器中央空调节能Abstract This article introduces the application of thermoelectric closed-loop control in the energy saving modification of Central Air-conditioning System. The thermoelectric closed-loop control is composed of frequency-changer, PLC, Digital-to-Analog Conversion module, temperature module, temperature transducer and other devices. Chilled water pump and cooling water pump can be in motion in variable speed automatically with the change of air-conditioning load through the thermoelectric closed-loop control. That optimized the operation quality of system greatly and notable effect of energy conservation can be seen.First, this paper will analyze the feasibility of energy saving modification after analysis of the original Central Air-conditioning system and its existing problems. Then it will put forward specific scheme of energy saving modification and briefly introduce the main equipment needed in energy saving modification. Again through the blue print it will draw up converter energy saving technique block diagram and PLC control ladder diagram and carry out the analysis of principle of PLC frequency-changer energy saving modification and PLC instruction list. At last, equipment debugging and problems met will be listed and there will be a comparison of operation effect before and after the modification and reconstruction of central air-conditioning. The emphasis and difficulty of this article is: analysis of the feasibility of energy saving modification and confirmation of specific scheme of energy saving modification, as well as, converter energy saving technique, prin