PLC Basics 5
PLC Programming 5
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Basics of an Electrical Control Panel (Review)
We get many questions about the basics of electrical control panels, such as what devices and equipment we typically use, how the devices are wired, how to keep the control panel and the cabinet within a normal temperature range and so on.
To answer some of these questions, we decided to go to one of our partner’s workshop and shoot a practical video reviewing an actual electrical control panel, for you to see what the basic components of a control panel are, how they are wired, the function of a thermostat and so on.
This is a 2-door control panel that is used for a system that turns wastewater into clean water.
Here is a summary of what you will learn after watching this video:
• We name control panels based on the number of doors that they have. For example, one-door, two-door or three-door control panel enclosures depending on how big of a panel you have. The more equipment and devices you have, the larger the control cabinet you will need.
• We usually have some switches that are connected to the PLC inputs and outputs. For example, one of these switches could be ’Mute Buzzer’. This is the button that you use and press when there is an active alarm on the system.
• You use the big red Emergency Shutdown push button or the E-Stop as it’s often called to shut down the whole system when there is an emergency.
•A PLC is a unit that usually includes a CPU and a few input and output cards.
•What is the difference between a “Wire” and a “Cable”? A wire is a single conductor but a “cable” is a group of wires that are covered in a jacket.
•You need to label each wire to be able to make the uniquely identifiable, which helps with troubleshooting if there is an issue.
• Sometimes we have two power supplies in this control panel with different output voltage. That is simply because we have some devices in the control panel that works with 24 volt DC and some other devices that work with 12 Volt DC.
• The reason that in this control panel the 24 Volt power supply is bigger in size is simply that here we have more devices that need 24 VDC to be turned on.
• We usually size the power supplies based on the amount of current output that we need. For example, we have power supplies with 1 Amp, 3 Amp, 5 Amp, 10 Amp, and 20 Amp output current. The more devices we have, the more current we need and the bigger the power supply gets.