PLC在三相异步电动机运行控制中的应用

Application of PLC in Control of Asynchronous Motor Operation

研究目的:通过对几个PLC控制程序的分析,使读者了解PLC程序的基本指令、控制方式和编程思想,初步掌握PLC的编程方法。研究方法:利用FX2N型PLC,根据生产工艺要求,设计了3个PLC在三相异步电动机控制中的应用程序,给出了输入/输出(I/O)接线图、程序控制梯形图及指令语句表。参照梯形图在计算机上利用专用编程软件“FXGP-WIN-CN”编制PLC的梯形图,并转换成指令语句表。用编程电缆连接计算机和PLC主机,执行“写出”操作,将指令语句表写出到PLC主机。“写出”程序是将计算机内的指令语句表程序写出至PLC主机的用户程序存储器。写出完成,即可联机调试。研究结果:通过上述研究方法和过程,帮助读者实现研究目的。研究结论:PLC的控制方式是由继电器控制方式演化而来,由PLC内部的微电子电路构成的软元件线圈和触点取代了硬件继电器的线圈和触点,用PLC的程序指令取代继电器控制的连接导线,将各个元件按照一定的逻辑关系连接起来,PLC内部的中央控制器(CPU)根据输入条件和预定的程序,控制各个软元件的状态,并输出到外部执行部件,控制生产设备运行。

Research purposes： The purpose was to make readers to learn the basic instruction, control way, programming concept and programming method through the analysis of several control programmes of PLC Research methods： According to the requirements of production process, three programmes of PLC applied in control of asynchronous motor were designed by adopting PLC model FX2N. The I/O wiring diagram, ladder diagram of programme control and instruction statement list were presented. The ladder diagram of PLC was programmed by adopting special software of ＂FXGP - WIN - CN＂ through learning experience of the diagram and the ladder diagram was also transferred into instruction statement list. The instruction statement list was written down into PLC processor by entering instruction of ＂write down＂ through connecting computer with PLC processor by cable. The ＂write down＂ programme was to make the instruction programme of statement list written down into the random of subscriber programme of PLC processor. The on- line test could be done after finishing ＂writing down＂. Research results： The research purpose could be realized through adopting the research method and process mentioned above. Research conclusions： The control way of PLC was derived from the control way of relay. The soft element＇s coils and contacts composed of micro electric circuits in PLC took place of the coils and contacts of relay and the programme orders of PLC took place of control wires of relay. With certain logical relation to connect every element, the CPU for PLC controlled the status of every soft element and transferred it to the outside execution elements to control the operation of device.