PLC Power supplies

Nearbyatom

Member
Join Date
Jul 2017
Location
USA
Posts
38
Some PLC manufacturers sell power supplies that attach to the left of the PLC CPU modules (see controllogix and automation direct click's PLC). Do we need these? What's the advantage? What's the use if I have my own (and big enough) power supply?
 
Mostly, it’s because not all power supplies are created equal and a poorly performing one can affect PLC functionality or reliability. Using the designated power supply gives you “one throat to choke”.

Also though, some of these connect directly to the backplane or power bus of the PLC, and you may not have terminal blocks to connect an outside power supply anyway
 
Why risk damaging or destroying your rack and all the I/o modules by using your power supply? Use the manufacturers power supply and if something goes wrong, their on the hook.

if you use yours and send the rack and I/o in or the ab rep sees what you have done, no warranty and you have to buy all new equipment.

james
 
As long as you have the supply that is specified and protected then go ahead and power the CPU from your own power supply.
I have seen some power supplies that also power up the bus system(s) as well as the CPU. Check the manufacturer to ensure that you can use an external supply.
Attached is the specifications for the Productivity 1000 CPU that can be supplied by an external source.

Regards,

productivity power supply.png
 
Honestly it's more a topology thing and customization than anything else by the manufacturers.

Most Siemens PLC's take in 24V and do the conversion into whatever voltages required inside the CPU, for example.
CLX allows you to choose how to power the rack by letting you specify the power supply to fit in it.

Whatever the design, you can achieve with more than one brand, it's how you piece and what pieces you put together that make the difference.
 
With Automation Direct Click, the power supply saves space.
If I need more current, I use my own supply.
Don't know about ControlLogix.
 

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