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在各类技工院校的PLC理论和实训教学中,总有一些难点困惑着初次接触PLC的人们,特别是已完全熟悉继电控制电路的人。根据学习摸索,总结出以下几点在PLC理论和实训教学中易忽视的问题:一是PLC控制电路与传统继电控制电路的异同问题;二是输入软继电器(X)和输出软继电器(Y)的问题;三是软继电器线圈与其触点的文字标号问题;四是外部输入信号触点类型问题;五是PLC接线时的电源问题;六是PLC公共端问题。
There are always some difficulties in PLC theory and practical training in various mechanic colleges and universities. People who first encounter with PLC, especially those who are completely familiar with the relay control circuit, are confused. According to learn groping, summed up the following points in the PLC theory and practical teaching easy to overlook the problem: First, PLC control circuit and the traditional relay control circuit similarities and differences between the problem; the second is the input soft relay (X) and output soft relay Y); Third, the text of the soft-relay coil and its contact problems; Fourth, the external input signal contact type problems; Fifth, PLC wiring power problems; Sixth, PLC common problems.