A402KC工业自动化 控制模块 DCS PLC系统

A402KC工业自动化 控制模块 DCS PLC系统

A402KC工业自动化 控制模块 DCS PLC系统

基本组件

PLC由几个基本部分组成。它们可能看起来与各个制造商略有不同，但每个组件的用途和范围是相同的。其中包括电源、中央处理单元 (CPU)、输入/输出卡以及放置输入/输出 (I/O) 卡的背板或机架。

如图 2 所示，背板在所有独立组件之间建立了电气连接，从而为 PLC 提供了模块化设计。这种电连接包括电源和通信信号。许多 PLC 制造商在背板上使用专有通信协议，以便 I/O 可以安全地与 CPU 通信。

电源

根据应用和安装环境，电源可接受 120VAC 或 24VDC。如上所述，此电压通过背板为 CPU 和 I/O 模块提供电源，这些模块以“卡”的形式出现。这些卡可以从它们在载体中的插槽中快速添加或移除。

需要注意的是，CPU 的电源并不为传感器和线圈等现场设备供电。此电源连接必须单独与卡建立。

中央处理器 (CPU)

CPU 是 PLC 的实际“大脑”，使其成为计算机。即使是小型的非模块化 PLC 也包含一个 CPU。输入信号来自 I/O 卡，逻辑程序根据信号做出决策。如果需要，CPU 然后命令输出随着信号和条件的变化而打开和关闭。

程序可能包括高级功能，例如数学运算、计时、计数和通过现代网络协议共享信息。对于较旧的中继系统，其中许多操作即使不是不可能，也是极其困难的。

A402KC工业自动化 控制模块 DCS PLC系统

Basic component

A PLC consists of several basic parts. They may look slightly different from individual manufacturers, but the purpose and scope of each component is the same. These include the power supply, the central processing unit (CPU), the input/output card, and the backplane or rack that houses the input/output (I/O) card.

As shown in Figure 2, the backplane establishes electrical connections between all the individual components, thus providing a modular design for the PLC. This electrical connection includes a power supply and a communication signal. Many PLC manufacturers use proprietary communication protocols on the backplane so that I/O can securely communicate with the CPU.

Power source

Depending on the application and installation environment, the power supply can accept either 120VAC or 24VDC. As mentioned above, this voltage supplies power to the CPU and I/O modules through the backplane, which come in the form of "cards." These cards can be quickly added or removed from their slots in the carrier.

It should be noted that the CPU's power supply does not power field devices such as sensors and coils. This power connection must be established separately from the card.

Central Processing Unit (CPU)

The CPU is the actual "brain" of the PLC, making it a computer. Even small non-modular PLCS contain a CPU. The input signal comes from the I/O card, and the logic program makes decisions based on the signal. If needed, the CPU then commands the output to turn on and off as signals and conditions change.

Programs may include advanced functions such as mathematical operations, timing, counting, and sharing information over modern network protocols. Many of these operations are extremely difficult, if not impossible, for older relay systems.