Parallel 24V DC power supply for control panel? Possible?

flyers

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Hi guys,

I'm designing a control panel system and one of the require from customer is to have parallel (2 units) power supply (24V DC) for the control panel & PLC as well.

There is one incoming 230V AC to the 2 units of power supply (230V AC to 24V DC). Each 24V DC power supply output will energize a relay & a pilot lamp (24V DC). in the event if any of the 24V DC power supply is faulted the relay wiil be de-energize and send an OFF signal to the PLC DI and the pilot lamp for that particular power supply will also be OFF.

My concern is do we need to put a diode after the power supply output, after the relay & pilot lamp so there is no current flow backward? Or izzit possible/advisible to do so?

I'm not sure what problem will I be facing, please advise me....thanks a lot.
 
You can by power supplies already designed to be used in parallel. Attached is a manual for Idecs that have some models that can be used parallel. I believe Sola makes some also.
 
The output internal to a SMPS supply is transformer winding - diode - cap. The problem is the regulator circuit. Most likely, the higher voltage SMPS would drive, while the other would go into shutdown.
If both were linears, they might oscillate with each other.

As suggested, the supplies neeed to be designed for this. The diode idea is safer (no question about supply design) and may be cheaper depending on how much labor is involved in wiring.
Add diodes and set both supplies for 24.7 or so. That will provide isolation, and eliminate any questions.

Supplies with a status output may prove to be the best solution.
 
If the power supplies are not designed for parallel operation, then definitely isolate them with diodes. Just make sure the diodes can handle the current involved and they have adequate heat sinking.
 
I combine switchmodes all the time throughg bridge rectifiers to give redundancy of 24VDC supply. Easy and reliable. Mount the rectifiers directly on the cubicle mounting plate.
 
Great Idea. I had visions of diodes soldered inline and didn't like it. A 25 amp or larger bridge will have a mounting hole in the middle, and .25" blade connections. Much better and cleaner.
 
Using a bridge rectifier is a good idea. I have used diodes in the past bolted through an aluminium heat sink for this purpose.

It is a good idea to independantly adjust each power supply so that their output voltages match and they will then share the load fairly equally. Remember that there will be a small voltage drop through the diodes so make the voltage adjustments with the diodes in the circuit.
 
Apply the outputs of the two power supplies at "PS1" and "PS2". Take the output where indicated. The other two diodes aren't used.

Bridge.JPG
 
Hi guys,

Thanks for all the replies and info given, it's a great help for me.
I've spoke to the end user, since they are Taiwan based, thus they prefer to use Meanwell brand power supply (all other panles are using this brand, non redundant).
so, i've browse the meanwell website and I found out that this might be suitable for me;
http://www.meanwellusa.com/search/DR-RDN20/DR-RDN20-spec.pdf

But the site does not have 2 different incoming (230V AC), so we are connecting one 230VAC to 2 Meanwell power supply and parallel it's 24V DC output.

According to some of the info given by the gurus here, I need a diode to eliminate backflow when one power supply is down. But if i'm using this kind of Meanwell redundant power supply, do I still need to have a diode there?

Hope to hear from you guys again. Thanks.
 

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