24 V DC Power Supplies in parallel

[Orn Jonsson]

Is there any problem with connecting two or more 24V DC power supplies in parallel to get more Amps? I have one 40A supply on a large machine running 20 servo valves plus a bunch of I/O. After 16 years in service it appears as if the machine is now drawing more than the 960 Watts available and faults the SOLA HD power supply on a start up. If I disconnect two or more of the servo valves during power up, the supply holds ok, and then we bring those two valves back on line. So this problem only happens on a start-up. Probably inrush related. Current power supply is about 5 years old.

I was thinking of throwing a small 5 AMP sola PS in parallel with the 40Amp one.

Please advice if you have time.

 

[mylespetro]

I literally have a benchtop 24VDC supply on the desk behind me with the two channels paralleled to get more amps, so I think in theory it should be fine but I would definitely look into literature.

 

[m_turk]

It would work. But also, you could just move those few solenoids to the new supply. Both have it's advantages, but I think separated one is more "by the book"..

 

[JBA-DK]

it would work. But also, you could just move those few solenoids to the new supply. Both have it's advantages, but i think separated one is more "by the book"..

,,

 

[Orn Jonsson]

Thanks for the fast reply guys. I was trying to avoid rewiring hence the "scab on idea". Rewiring a few of the servo valves to a separate power supply would probably be preferred but in this case the incoming power to the machine is 480V so I would have to purchase large 480 V AC in 24 V DC out unit.
I have a 1000 W 110V AC transformer on the machine that I was thinking about using for the Amp boosting supply. I asked an EE fella about this the other day and he implied that there could be issues due to imbalance between the two supplies... Any concerns with this setup that you guys see? I am feeling brave and lucky at the moment - but that could change really fast...

 

[JBA-DK]

A small 480v to 24 VDC power supply. How expensive can it be??

 

[NetNathan]

Thanks for the fast reply guys. I was trying to avoid rewiring hence the "scab on idea". Rewiring a few of the servo valves to a separate power supply would probably be preferred but in this case the incoming power to the machine is 480V so I would have to purchase large 480 V AC in 24 V DC out unit.
I have a 1000 W 110V AC transformer on the machine that I was thinking about using for the Amp boosting supply. I asked an EE fella about this the other day and he implied that there could be issues due to imbalance between the two supplies... Any concerns with this setup that you guys see? I am feeling brave and lucky at the moment - but that could change really fast...

Yes.. I might be more prone to parallel the same size..'
If not...How is it handled if they are current limiting??

 

[m_turk]

Thanks for the fast reply guys. I was trying to avoid rewiring hence the "scab on idea". Rewiring a few of the servo valves to a separate power supply would probably be preferred but in this case the incoming power to the machine is 480V so I would have to purchase large 480 V AC in 24 V DC out unit.
I have a 1000 W 110V AC transformer on the machine that I was thinking about using for the Amp boosting supply. I asked an EE fella about this the other day and he implied that there could be issues due to imbalance between the two supplies... Any concerns with this setup that you guys see? I am feeling brave and lucky at the moment - but that could change really fast...

I don't understand why you wouldn't go with your plan for a small supply and a transformer, but separate them.. Yes, some rewiring, but it shouldn't be a big issue..
Also, it doesn't have to be the solenoids.. Maybe pick something more practical to rewire?

 

[GaryS]

You should never do it unless they are rated for parallel use master slave so to speak
the problem is that they will never regulate at exaxctly the same output vlotage and then the higher voltag unit will over load and fail causing both to fail.
there is a company that makes power supplies that are designed to do exactly that I ran into them as while back. I just can't remember the name

 

[NetNathan]

You should never do it unless they are rated for parallel use master slave so to speak
the problem is that they will never regulate at exaxctly the same output vlotage and then the higher voltag unit will over load and fail causing both to fail.
there is a company that makes power supplies that are designed to do exactly that I ran into them as while back. I just can't remember the name

Phoenix Contact for one...

 

[ASF]

GaryS makes an important point. It may work for a while, but if the two are trying to regulate the output at slightly different voltages, they will fight each other, and they will almost certainly fail prematurely.

Some DC power supplies are specifically designed for this, and you should use that type. You will need to replace both power supplies.

 

[Soggy Canuck]

On the machines I have worked on over the years that have duplexed (or triplexed) power supplies, they have always been identical supplies. One machine for sure was using Sola brand.

I had a Siemens parallel where one had failed, the nearest replacement was in the fatherland. Stuck an equivelant wattage Omron PS in until the correct unit arrived some 8 days later and it worked fine.

Don't use different wattage units, you'll let the smoke out, and before you ask, yes, I learned that the hard way on an earlier 2am callout.

 

[rupej]

The plain jane weidmullers we use are rated for up to 5 of them in parallel. I figure they also function as redundancy in addition to more available amps.

 

[chavak]

If you enough cash to spare, the easier fix would be replace the power supply with a higher wattage one and reserve this existing for other purpose

 

[L33er]

You should never do it unless they are rated for parallel use master slave so to speak
the problem is that they will never regulate at exaxctly the same output vlotage and then the higher voltag unit will over load and fail causing both to fail.
there is a company that makes power supplies that are designed to do exactly that I ran into them as while back. I just can't remember the name

Was it rack mounted? Sorensen?