使用PLC的自动化制造系统——电气接线图

3.5 ELECTRICAL WIRING DIAGRAMS

3.5电气接线图

When a controls cabinet is designed and constructed ladder diagrams are used to document the wiring. A basic wiring diagram is shown in Figure 3.9. In this example the system would be supplied with AC power (120Vac or 220Vac) on the left and right rails. The lines of these diagrams are numbered, and these numbers are typically used to number wires when building the electrical system. The switch before line 010 is a master disconnect for the power to the entire system. A fuse is used after the disconnect to limit the maximum current drawn by the system. Line 020 of the diagram is used to control power to the outputs of the system. The stop button is normally closed, while the start button is normally open. The branch, and output of the rung are CR1, which is a master control relay. The PLC receives power on line 30 of the diagram.

当设计和制造一个控制柜时，阶梯图就用于布线的记录。一个基本的接线图如图3.9所示。在这个例子中，系统将在左面和右面的线中提供交流电源（120Vac或220VAC）。这些图的线被编号，这些数字通常用来在构建电气系统时标识电线。在线号010前的开关是一个主断路器用来将整个系统的电源切断。断路器后的熔断器是限制系统的最大电流的。图中的020线是用来控制到输出系统的电源。停止按钮是常闭的，而开始按钮常开。输出的分支梯级CR1是一个主控接触器。PLC在图的30号线接收的电源。

 

 

In the wiring diagram the choice of a normally close stop button and a normally open start button are intentional. Consider line 020 in the wiring diagram. If the stop button is pushed it will open the switch, and power will not be able to flow to the control relay and output power will shut off. If the stop button is damaged, say by a wire falling off, the power will also be lost and the system will shut down - safely. If the stop button used was normally open and this happened the system would continue to operate while the stop button was unable to shut down the power. Now consider the start button. If the button was damaged, say a wire was disconnected, it would be unable to start the system, thus leaving the system unstarted and safe. In summary, all buttons that stop a system should be normally closed, while all buttons that start a system should be normally open.

在接线图中选择常闭的停止按钮和常开的启动按钮是有意的。考虑接线图的020线。如果停止按钮被按下，将打开开关，电源将无法流向控制继电器和输出电源将关闭。如果停止按钮损坏，例如电线脱落，将失去电源，系统将安全地关闭。如果停止按钮用常开，并且发生同样的事，系统将继续运行，因为停止按钮无法关闭电源。现在考虑启动按钮。如果这个按钮遭到破坏，比如说接线断掉，这仅保持系统无法启动系统，从而是安全的。总之，所有的停止系统的按钮应该是常闭的，而所有的启动系统的按钮应常开。