PF755 vs. 525

jraef said:

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.

Click to expand...

ceilingwalker said:

Thank you for the info. In this case, I might be a little concerned about torque control. Would you know how they compare in that area?

Click to expand...

jraef said:

The 525 does NOT do torque control. It does SVC and it can do Flux Vector Control with an encoder feedback, but only VELOCITY FVC, not torque. It doesn't have a torque regulator like the 755 does and the 755 can do encoderless FVC torque control. So yeah, not the same...


But you said it was a "flood pump", so is this some sort of lobe pump or other form of PD pump then? Because if it is centrifugal, torque control is pointless.

Click to expand...

Gene Bond said:

If cost is the issue (assuming simple Ethernet speed control is the *real* function), then why use Rockwell? Why not save some real money and use one of the other brands that are proven as (or better) reliable, readily available and most often less expensive?

Most of the top brands have AOI's just like Rockwell, assuming you are tied to Rockwell's PLC's.

Click to expand...

Gene Bond said:

If cost is the issue (assuming simple Ethernet speed control is the *real* function), then why use Rockwell? Why not save some real money and use one of the other brands that are proven as (or better) reliable, readily available and most often less expensive?

Most of the top brands have AOI's just like Rockwell, assuming you are tied to Rockwell's PLC's.

Click to expand...

seth350 said:

A compact or Contrologix with motion could utilize the 527 drive. It’s a CIP Motion only drive and will configure its parameters automatically. Throw in a managed Ethernet switch to complete the system.

I have only read about them, never used one.

The 755 can also be setup to do CIP Motion.
Both drives use the motion instructions included in logix5000 and studio5000.

Click to expand...

jraef said:

Just a slight correction on that (and I understand that you haven’t used one yet). There are no “parameters” in a 527, it is fully programmed as a motion axis using motion profiles and commands, so if you are not familiar with motion control systems and have an overall motion based system with other servos in it, I don’t recommend using a 527.

Click to expand...