525 PowerFlex Amp Question

I'm sure someone out there is a lot smarter than I, so here is the question. I have a PowerFlex drive the max. overcurrent is set at 6.0 amps I was monitoring it and it was running at 11.5 amps, why was it not faulting on overcurrent.
Thanks in advance for you help.

Depends on the parameter but most likely because the time base did not expire. Meaning that for an overload to occur the over current has to be greater than 6 Amps for xxx amount of time.

Where and how were you measuring 11.5 amps?

Which parameter are you referring to as the "max overcurrent" setting?

There is a timer for over current conditions addressing in rush/break out current. That being said your measurement is almost double the overload I. Perhaps this VFD is undersized or your process has changed. Be on your toes, I've had a drive explode near me before. Pretty scary. Now back to my never ending HMI project, yay!

The PF 525 are very versatile VFDs. You have basic parameters and advanced parameters. Then you have appview settings that are designed for application usage and parameters are set that way. Conveyor usage is a appview. AppViews set bare necessity parameters for the desired application. While you can scroll around with the front keypad, that is like looking at everything through a keyhole, difficult to see the whole picture. Using RSLogix 5K or Studio, you should see ALL the parameters. Quite a few to sort through so put a pot of coffee on and take your time. If you do not see parameters in RS Logix, verify firmware and AOP, update as necessary via Ethernet as USB is painfully slow and has reliability issues. Control Flash 15.00 or higher is recommended. The manual is a wealth of knowledge as well.

With all that, back to your question, I cannot answer why you appear to be driving the motor and have overcurrent with the information you have given.

P033 will tell you what your actual OL current is, you can go as high as 2x the amp rating for your drive. It also has to be a sustained current or else it would fault every time the motor started. Some motors have a in rush current 8x their running current. your fuses should handle the short circuit current as well

I would add GRT instruction into PLC program to stop PF525 drive.
you have to set up one input for this motor current

If by “max current” you mean the motor nameplate current setting, that is for motor overload protection and is an “inverse time /current” trip function, meaning there is a curve to the trip time based on I squared t, with two defined points on the curve; 100% of the setting will never trip, 600% of the setting will trip in 10 seconds. Roughly guessing, 200% would likely be somewhere in the neighborhood of 30 seconds.

If you never want the drive to output more than 6A, you need to either set the Jam protection trip to 6A and no delay, or set it to current limit, in which case it will override your speed setting to try to shed load in order to limit current.

Side note: there is no motor inrush when you have a VFD, it totally controls that. You can accelerate a motor to full speed without ever exceeding the motor FLA if you want to, so long as acceleration time is not an issue.

I would look at parameter 33 and 34. Motor OL current and Motor NP FLA
Then there are the current limit settings
Parameter 484 and 485 as suggested there are defaults and you can set these too based on current limit settings.
You can also do a shear pin current limit, parameters 486 thru 489. This is an instantaneous trip.

jraef said:

If by “max current” you mean the motor nameplate current setting, that is for motor overload protection and is an “inverse time /current” trip function, meaning there is a curve to the trip time based on I squared t, with two defined points on the curve; 100% of the setting will never trip, 600% of the setting will trip in 10 seconds. Roughly guessing, 200% would likely be somewhere in the neighborhood of 30 seconds.

If you never want the drive to output more than 6A, you need to either set the Jam protection trip to 6A and no delay, or set it to current limit, in which case it will override your speed setting to try to shed load in order to limit current.

Side note: there is no motor inrush when you have a VFD, it totally controls that. You can accelerate a motor to full speed without ever exceeding the motor FLA if you want to, so long as acceleration time is not an issue.

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Well I stand corrected, I did not know there was no inrush current with VFD's. I guess you learn something new every day! Thanks for the info.

BClark4 said:

Well I stand corrected, I did not know there was no inrush current with VFD's. I guess you learn something new every day! Thanks for the info.

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I've been seeing more and more customers using VFDs as soft starts lately, particularly Powerflex 525s. I'm assuming that they're substantially cheaper than an AB SMC soft start these days.

mylespetro said:

I've been seeing more and more customers using VFDs as soft starts lately, particularly Powerflex 525s. I'm assuming that they're substantially cheaper than an AB SMC soft start these days.

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Not quite - but I have done that myself once where I needed a soft start on a reversing motor. It was only a little 0.37kW motor, and by the time you factor in a soft starter, reversing contactors, all the I/O that goes with it, and the additional labour costs for wiring it, the cost worked out almost the same to throw a PF525 in there and plug in an ethernet cable. And also the cabinet looked much neater so my OCD was happy

ASF said:

Not quite - but I have done that myself once where I needed a soft start on a reversing motor. It was only a little 0.37kW motor, and by the time you factor in a soft starter, reversing contactors, all the I/O that goes with it, and the additional labour costs for wiring it, the cost worked out almost the same to throw a PF525 in there and plug in an ethernet cable. And also the cabinet looked much neater so my OCD was happy

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I almost always use a 525 instead of a softstart. So much more control and data collection back for the cost. I rarely even use contactors any more. Customers are willing to pay the cost for the monitoring alone.