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 UO 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.
2006, Vol. 23 
