PF755 vs. 525

ceilingwalker

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Hello all,

I have a system with several flood pumps (15HP), controlled by Power Flex 755's. In an effort to save some $ I would like to use PF525's. I can't see any reason why I can't, I don't believe I need a very intelligent drive with all the bells and whistles. These are simple single-speed motors with centrifugal pump on the end. I want to make sure there isn't something I am missing, as to why someone would have used the 755 to begin with. It is an old enough system that the 525 may not have been available when these were purchased.....maybe. I just wanted to make sure, before I purchase.

Thank you
 
Since it sounds like it's existing equipment, I would advise that you inspect the drive programming in detail, this will tell you if the new drive will work or not.

I have used this method for a long time, switching between drive models and manufacturers, It works .
 
Are they all controlled over Ethernet/IP or CIP Motion?
If not, a 753 would be a tad bit cheaper and be the same size. The difference is that the 753 has I/O and no Ethernet.

I have never understood what makes one drive “better” than another.
You just need to buy the features you need. The 755 has a whole lot of fluff for different situations to be running a pump without any frills.

Automation Direct has some new drives that seem pretty feature rich.
 
ceilingwalker said:
Hello all,

I have a system with several flood pumps (15HP), controlled by Power Flex 755's. In an effort to save some $ I would like to use PF525's. I can't see any reason why I can't, I don't believe I need a very intelligent drive with all the bells and whistles. These are simple single-speed motors with centrifugal pump on the end. I want to make sure there isn't something I am missing, as to why someone would have used the 755 to begin with. It is an old enough system that the 525 may not have been available when these were purchased.....maybe. I just wanted to make sure, before I purchase.

Thank you...

...I need the Ethernet Control...

I'm a little confused as to your thinking here?...

If the pumping system is operational for some time now (years?) with PowerFlex 755 drives, then what is the primary reason for you wanting to change to any other drive? If they are long since bought and paid for then I cannot see how purchasing new drives will save money here?

If you now require more "modern" Ethernet control/feedback of these drives, as opposed to say an original setup using the drive's digital I/O, then why not just use Ethernet with the existing drives? Are you aware that the PowerFlex 755 drives feature an embedded Ethernet/IP adapter? seth350 was alluding to this fact when asking "Are they all controlled over Ethernet/IP or CIP Motion?". These on-board adapters provide 16 in and 16 out 32-bit Datalinks for integration into a Logix 5000 application.

Even if you were using an older drive that did not have embedded Ethernet, but does have the option to add an adapter; I would still most likely advise that one be added, rather than replacing the entire drive just to add Ethernet.

Maybe I'm overlooking something here, like perhaps you are just referencing an existing system's components so as to specify similar for a new system you are designing, while attempting to use newer equivalent equipment?

To clarify - Are you looking to replace the existing drives in the system you have mentioned in the opening post or are you designing a similar but new system?

Regards,
George
 
Last edited:
AustralIan said:
I assumed he was duplicating the system in another location.

Maybe he's duplicating it in the same location, but using it in another location?

Hehe, these open interpretations!

Yep, It can certainly be read that way when you look at it a couple of times, hence my final thoughts, and I reckon your are on the money, but it isn't clearly stated, so l just wanted to confirm it all the same.

As a proposition - the PowerFlex 525 drives are quite capable for use in simple pumping and fan applications. Certain parameters may need careful attention, but still capable, none the less.

Regards,
George
 
At that HP and that application, it’s almosr a toss-up. But there IS a difference.

The 750 series is an “Architecture” Class drive, they are designed with the end user in mind, so they are designed to last. The components used are selected for life expectancy and they are repairable in the future. The 755 has a lot more performance capability, but those are probably moot on a centrifugal pump application. One thing it does have however that the others don’t is what’s called “DeviceLogix” programming capability, essentially a small PLC embedded into the drive to where you can run programs and control I/O in the VFD application or even separately. That’s one thing you should double check, because the 520 drives don’t have that feature.

The 520 series drives are “Component Class” drives meaning they are parts and are essentially “consumeable” in that if something happens, you replace it. They are mostly targeted for volume OEM sales to be competitive with other similar drives, so component selection is shifted toward being lower cost and they are not designed to be repaired in the future. The one caveat however is that the 520 series has two modules, power and control, so it is “partially” repairable in that if one or the other module fails someday, you only need to replace that half of the drive. The other general difference is that with Rockwell, all Architecture drives have a DC bus choke, which comes with some long term life expectancy benefits, whereas Component class drives typically do not. HOWEVER, in this specific case, a 15HP and up PF525 does happen to have a DC bus choke. Hence the toss-up decision in this specific case.
 
Not knowing anything about these drives I just browsed over a selection guide.
http://literature.rockwellautomation.com/idc/groups/literature/documents/sg/pflex-sg002_-en-p.pdf

My advice would to be to look at the 755 and start crossing off things you don't need and see if you end up with a 525. About the only thing I can see that you might want on a 755 is the direct access to the drive I/O. But from your description it doesn't sound like it.

I think the only thing to consider would be torque control of the 525 vs. 755. I might need tight torque control but am not sure what the 525 offers for that.
 
I'm a little confused as to your thinking here?...

If the pumping system is operational for some time now (years?) with PowerFlex 755 drives, then what is the primary reason for you wanting to change to any other drive? If they are long since bought and paid for then I cannot see how purchasing new drives will save money here?

If you now require more "modern" Ethernet control/feedback of these drives, as opposed to say an original setup using the drive's digital I/O, then why not just use Ethernet with the existing drives? Are you aware that the PowerFlex 755 drives feature an embedded Ethernet/IP adapter? seth350 was alluding to this fact when asking "Are they all controlled over Ethernet/IP or CIP Motion?". These on-board adapters provide 16 in and 16 out 32-bit Datalinks for integration into a Logix 5000 application.

Even if you were using an older drive that did not have embedded Ethernet, but does have the option to add an adapter; I would still most likely advise that one be added, rather than replacing the entire drive just to add Ethernet.

Maybe I'm overlooking something here, like perhaps you are just referencing an existing system's components so as to specify similar for a new system you are designing, while attempting to use newer equivalent equipment?

To clarify - Are you looking to replace the existing drives in the system you have mentioned in the opening post or are you designing a similar but new system?

Regards,
George
Sorry, should have given a little more info. We are building another system that is more-or-less the same. I am evaluating all aspects of the job and of course saving money where I can.
 

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