The PLC Rack is the foundation on which the modules within the control system will reside. Once the rack is installed, the first module that should be installed is the Power Supply.

The video explains the use, installation, and function of the power supply module.

1) What is a Power Supply?

The power supply module is a necessary and important component of the control system. It is used to safely regulate and supply the voltage necessary for the PLC and other modules installed on the rack. The module is typically installed in the first slot of the rack.

2) Selecting a Power Supply

The output voltage of the power supply that we use is typically 24 volts DC. The output current varies depending on the number of the modules needed in the control system. For instance, this output current could be 2, 5 or 10 Ampere. Depending on which and how many modules are used, the output current of the power supply may need to be higher.

3) Wiring the module

The power supply is fed directly from a 110 or 220 Volt AC voltage power outlet that it’s plugged into. In turn, it usually converts that voltage into a 24 Volt DC voltage output that will safely power the PLC and other modules installed on the rack. To make this voltage available to the control system modules, we have to do the wiring between each individual module and the power supply. This wiring is also necessary with modular PLC’s. In compact PLC’s this wiring is internal and already built in therefore no wiring is necessary. In some cases the power supply can be connected to the CPU using a U-shaped connector.

4)Communication with the power supply

The power supply, unlike the rest of the PLC modules, has no data communication with the CPU or any other modules. The only purpose for the power supply is to supply a safe DC voltage to the modules in order for them to function properly. You will not see any bus connections and will not need to install any between the power supply and the rest of the PLC modules because there are no communications between them.

5) How do I know it’s working

The voltage and current levels are tested at the manufacturer to ensure that the power supply will safely regulate the necessary voltage needed for the modules. If however, you need to determine that the module is functioning properly, you may easily do so using a voltmeter. Some power supplies are equipped with a small internal relay and an opened or closed contact that will be opened/closed in the event of a power failure. Wiring this contact to an input in the control system may be used to determine a power loss.

To summarize, the power supply is a necessary and important module within the control system. This module safely regulates and supplies power to all of the other modules installed on the rack.